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LeetCode 3933 - Largest Local Values in a Matrix II

LeetCode Problem 3933 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution Problem Understanding The problem asks us to find local maximums in a 2D matrix according to a specialized neighborhood rule. Each cell in the matrix has a value x . A cell is a local maximum if it is non-zero and no neighboring cell within a distance of x in both row and column has a strictly greater...

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LeetCode 3926 - Count Valid Word Occurrences

LeetCode Problem 3926 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting Solution Problem Understanding The problem asks us to count occurrences of specific words in a string that is formed by concatenating an array of smaller string "chunks". The twist is that words are defined in a non-standard way: they can include joiner hyphens , which are hyphens that appear between two lowercase English letters. Any other character, including...

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LeetCode 3891 - Minimum Increase to Maximize Special Indices

LeetCode Problem 3891 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy, Prefix Sum Solution Problem Understanding This problem asks us to modify an integer array to create as many special indices as possible, where a special index i is one where nums[i] > nums[i-1] and nums[i] > nums[i+1] . We can only increase values in the array, one unit at a time, and our goal is to maximize the number...

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LeetCode 3843 - First Element with Unique Frequency

LeetCode Problem 3843 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Correctness The proposed solution does not answer the question that Exercise 4.3.1.17 asks. The exercise is specific: given that $v_{n-1} \ge \lfloor b/2 \rfloor$ and $u_n = v_{n-1}$, one must show that the quotient digit $q$ in the division step satisfies $q = b-1$ or $q = b-2$. This is a statement about bounds on the first quotient...

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LeetCode 3687 - Library Late Fee Calculator

LeetCode Problem 3687 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding The problem asks us to calculate the total late fee for a library based on how many days each book was returned late. You are given an integer array daysLate , where each element daysLate[i] represents the number of days the i-th book was returned past its due date. The penalty rules are tiered: if a book is...

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LeetCode 3672 - Sum of Weighted Modes in Subarrays

LeetCode Problem 3672 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window, Counting, Ordered Set Solution Problem Understanding The problem asks us to calculate the sum of weighted modes for all subarrays of length k in a given array nums . Each subarray is contiguous and has exactly k elements. For a subarray, the mode is the element that occurs most frequently. If multiple elements share the same highest frequency,...

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LeetCode 3761 - Minimum Absolute Distance Between Mirror Pairs

LeetCode Problem 3761 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math Solution Correctness The proposed solution does not answer the question that Exercise 4.3.1.17 asks. The exercise is specific: given that $v_{n-1} \ge \lfloor b/2 \rfloor$ and $u_n = v_{n-1}$, one must show that the quotient digit $q$ in the division step satisfies $q = b-1$ or $q = b-2$. This is a statement about bounds on the first quotient...

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LeetCode 3656 - Determine if a Simple Graph Exists

LeetCode Problem 3656 Difficulty: 🟡 Medium Topics: Array, Binary Search, Graph Theory, Sorting, Prefix Sum Solution Correctness The proposed solution explains in detail how Algorithm S computes subtraction in radix $b$ and how the complement-based correction works when a final borrow occurs. However, the exercise asks specifically to show that if $u_n = v_{n-1}$, then $q = b - 1$ or $b - 2$ , where $q$ is presumably the...

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LeetCode 3645 - Maximum Total from Optimal Activation Order

LeetCode Problem 3645 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem involves determining the maximum total value achievable by activating elements in an array under a set of constraints. We are given two arrays, value and limit , both of length n . Each element starts inactive, and activating an element adds its corresponding value[i] to the total. However, activation is...

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LeetCode 3631 - Sort Threats by Severity and Exploitability

LeetCode Problem 3631 Difficulty: 🟡 Medium Topics: Array, Sorting Solution Problem Understanding The problem gives a list of threats, where each threat is represented as a triplet [IDi, sevi, expi] . Each threat has a unique identifier, a severity value, and an exploitability value. From these two attributes, a derived metric called score is defined as score = 2 × severity + exploitability . The task is to reorder the...

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LeetCode 3575 - Maximum Good Subtree Score

LeetCode Problem 3575 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search, Bitmask Solution LeetCode 3575 - Maximum Good Subtree Score Problem Understanding We are given a rooted tree with n nodes. Node 0 is the root, and the tree structure is described by the parent array par , where par[i] is the parent of node i . Each node contains an integer value vals[i] . For...

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LeetCode 3576 - Transform Array to All Equal Elements

LeetCode Problem 3576 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks whether it is possible to transform an array of integers containing only 1 and -1 into an array where all elements are equal by performing at most k operations. Each operation consists of selecting an index i (from 0 to n-2 ) and multiplying both nums[i] and nums[i + 1] by -1 . The array...

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LeetCode 3473 - Sum of K Subarrays With Length at Least M

LeetCode Problem 3473 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem gives an integer array nums , together with two integers k and m . We must choose exactly k non-overlapping subarrays, and every chosen subarray must have length at least m . Among all valid choices, we want the maximum possible total sum. A subarray is a contiguous segment of the array. Non-overlapping...

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LeetCode 3485 - Longest Common Prefix of K Strings After Removal

LeetCode Problem 3485 Difficulty: 🔴 Hard Topics: Array, String, Trie Solution Problem Understanding This problem asks us to calculate the longest common prefix (LCP) among any k strings from a list of strings, after removing each string in turn . Specifically, for each index i , we remove words[i] from the array, then find the longest prefix shared by any k remaining strings. The output is an array where each...

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LeetCode 3410 - Maximize Subarray Sum After Removing All Occurrences of One Element

LeetCode Problem 3410 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Segment Tree Solution Solution Algorithm S performs digit-by-digit subtraction in radix $b$ without requiring knowledge of whether $(u_{n-1}\ldots u_0) b \ge (v {n-1}\ldots v_0) b$. It produces digits $w_0, w_1, \ldots, w {n-1}$ and a final borrow $k \in {0,-1}$, where $k=-1$ occurs if and only if $u < v$. Assume Algorithm S is executed without prior ordering of the...

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LeetCode 3934 - Smallest Unique Subarray

LeetCode Problem 3934 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Rolling Hash, Suffix Array, Hash Function Solution Problem Understanding The problem asks us to find the smallest possible length of a contiguous subarray such that there exists at least one subarray of that length that appears exactly once in the entire array. In other words, for a fixed length L , we look at every subarray of size...

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LeetCode 3928 - Minimum Cost to Buy Apples II

LeetCode Problem 3928 Difficulty: 🔴 Hard Topics: Array, Graph Theory, Heap (Priority Queue), Shortest Path Solution Problem Understanding The problem asks us to determine the minimum cost to purchase apples starting from each shop, taking into account two types of costs: the local price of apples at each shop and the transportation costs along roads connecting the shops. Each road has a base cost to traverse when empty and a...

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LeetCode 3927 - Minimize Array Sum Using Divisible Replacements

LeetCode Problem 3927 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy, Number Theory Solution Problem Understanding The problem gives an integer array nums and allows an operation that can reduce values under a divisibility condition. Specifically, you may choose two indices a and b such that nums[a] % nums[b] == 0 , and then replace nums[a] with nums[b] . The effect of this operation is that any number in...

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LeetCode 3925 - Concatenate Array With Reverse

LeetCode Problem 3925 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding The problem asks us to construct a new array by concatenating an input array with its reversed version. Given an integer array nums of length n , we must return a new array ans of length 2 * n . The first n elements of ans are exactly the same as nums , preserving order. The next n...

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LeetCode 3904 - Smallest Stable Index II

LeetCode Problem 3904 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem gives an integer array nums of length n and an integer k . For every index i , we split the array into two overlapping parts: The prefix nums[0..i] The suffix nums[i..n-1] For that index, we compute an instability score: $$\text{instability}(i)=\max(nums[0..i])-\min(nums[i..n-1])$$ An index is considered stable if this value is less than or equal to...

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LeetCode 3923 - Minimum Generations to Target Point

LeetCode Problem 3923 Difficulty: 🟡 Medium Topics: Array, Hash Table, Simulation Solution LeetCode 3923 - Minimum Generations to Target Point Problem Understanding This problem defines a process that repeatedly creates new 3D points from existing points. We begin with the given list points , which forms generation 0 . For every later generation, we consider all distinct points that have been created so far, including points from every previous generation....

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LeetCode 3921 - Score Validator

LeetCode Problem 3921 Difficulty: 🟢 Easy Topics: Array, String, Simulation Solution LeetCode 3921 - Score Validator Problem Understanding This problem asks us to simulate a simple scoring system while processing a sequence of event strings from left to right. We are given an array called events , where each element represents one event. Two variables are maintained throughout the simulation: score , initially 0 counter , initially 0 Each event...

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LeetCode 3920 - Maximize Fixed Points After Deletions

LeetCode Problem 3920 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sorting Solution Problem Understanding The problem asks us to maximize the number of fixed points in an array after performing deletions. A fixed point is an index i such that nums[i] == i . We are allowed to delete any number of elements from the array, and after each deletion, all remaining elements shift left, which reassigns the indices starting...

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LeetCode 3919 - Minimum Cost to Move Between Indices

LeetCode Problem 3919 Difficulty: 🟡 Medium Topics: Array, Greedy, Prefix Sum Solution LeetCode 3919 - Minimum Cost to Move Between Indices Problem Understanding We are given a strictly increasing array nums . Each position represents an index in the array, and we want to move between indices as cheaply as possible. For every index x , a special neighbor called closest(x) is defined. Since the array is strictly increasing, each...

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LeetCode 3917 - Count Indices With Opposite Parity

LeetCode Problem 3917 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3917 - Count Indices With Opposite Parity Problem Understanding The problem gives us an integer array nums of length n . For every index i , we must determine how many indices to its right contain a number with the opposite parity. Parity refers to whether a number is even or odd: Even numbers have a remainder of 0 when...

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LeetCode 3914 - Minimum Operations to Make Array Non Decreasing

LeetCode Problem 3914 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3914 - Minimum Operations to Make Array Non Decreasing Problem Understanding We are given an array nums . In a single operation, we choose any contiguous subarray and increase every element in that subarray by the same positive integer value x . The cost of an operation is exactly the chosen value x . If we perform multiple operations,...

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LeetCode 3915 - Maximum Sum of Alternating Subsequence With Distance at Least K

LeetCode Problem 3915 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Segment Tree Solution Correctness The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger. It correctly uses the standard TAOCP idea: if a final borrow remains, then the computed digit string represents a complement representation, and an additional...

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LeetCode 3912 - Valid Elements in an Array

LeetCode Problem 3912 Difficulty: 🟢 Easy Topics: Array Solution Correctness The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger. It correctly uses the standard TAOCP idea: if a final borrow remains, then the computed digit string represents a complement representation, and an additional correction step is needed...

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LeetCode 3911 - K-th Smallest Remaining Even Integer in Subarray Queries

LeetCode Problem 3911 Difficulty: 🔴 Hard Topics: Array, Binary Search Solution Problem Understanding The problem provides a strictly increasing integer array nums and a list of queries, each consisting of [li, ri, ki] . For each query, we consider the subarray nums[li..ri] and remove all elements of this subarray from the infinite sequence of positive even integers . The task is to determine the kith smallest number remaining in that...

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LeetCode 3909 - Compare Sums of Bitonic Parts

LeetCode Problem 3909 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem gives us a bitonic array nums , meaning an array that first strictly increases to a single peak element and then strictly decreases. The task is to split this array into two overlapping parts: The ascending part , which includes all elements from the start of the array up to and including the peak. The descending part...

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LeetCode 3910 - Count Connected Subgraphs with Even Node Sum

LeetCode Problem 3910 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory, Enumeration Solution Correctness The solution does address the correct exercise and correctly identifies that the task is to generalize Algorithm S by handling the case when subtraction is performed without knowing which operand is larger. It correctly uses the standard TAOCP idea: if a final borrow remains, then the computed digit string represents...

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LeetCode 3905 - Multi Source Flood Fill

LeetCode Problem 3905 Difficulty: 🟡 Medium Topics: Array, Breadth-First Search, Matrix Solution Problem Understanding The problem asks us to simulate a multi-source flood fill on an n x m grid. Each element of the sources array represents a starting point with a specific color, and all other cells start uncolored, represented as 0. At each time step, the currently colored cells spread their color to their four immediate neighbors (up,...

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LeetCode 3903 - Smallest Stable Index I

LeetCode Problem 3903 Difficulty: 🟢 Easy Topics: Array, Prefix Sum Solution Problem Understanding The problem asks us to find the smallest index i in an integer array nums such that the instability score at that index is less than or equal to a given integer k . The instability score is defined as the difference between the maximum of the prefix nums[0..i] and the minimum of the suffix nums[i..n-1] ....

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LeetCode 3892 - Minimum Operations to Achieve At Least K Peaks

LeetCode Problem 3892 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution LeetCode 3892 - Minimum Operations to Achieve At Least K Peaks Problem Understanding We are given a circular array nums . An index is considered a peak if its value is strictly greater than both of its neighbors. Because the array is circular, the first and last elements are adjacent. For example, the neighbors of index 0 are nums[n...

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LeetCode 3886 - Sum of Sortable Integers

LeetCode Problem 3886 Difficulty: 🔴 Hard Topics: Array, Math, Sorting, Enumeration Solution Problem Understanding The problem asks us to find all integers k that divide the length of the input array nums and for which the array can be sorted into non-decreasing order using a very specific operation. The operation is to partition nums into consecutive subarrays of length k and then cyclically rotate each subarray independently any number of...

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LeetCode 3874 - Valid Subarrays With Exactly One Peak

LeetCode Problem 3874 Difficulty: 🟡 Medium Topics: Array, Math Solution Problem Understanding The problem asks us to count the number of contiguous subarrays of a given integer array nums that contain exactly one peak , where a peak is defined as an element nums[i] that is strictly greater than both its immediate neighbors nums[i-1] and nums[i+1] . Furthermore, for a subarray to be valid, the distance from the peak to...

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LeetCode 3861 - Minimum Capacity Box

LeetCode Problem 3861 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem presents a straightforward search scenario. You are given an array capacity where each element represents the storage capacity of a box. You are also given an integer itemSize , representing the size of an item you want to store. The task is to find the index of the box that has the smallest capacity that is still...

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LeetCode 3859 - Count Subarrays With K Distinct Integers

LeetCode Problem 3859 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sliding Window, Counting Solution Problem Understanding This problem asks us to count subarrays of a given integer array nums such that each subarray contains exactly k distinct integers , and each distinct integer in the subarray appears at least m times . In other words, for a subarray to be valid, it must satisfy two constraints: a cardinality constraint (exactly...

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LeetCode 3824 - Minimum K to Reduce Array Within Limit

LeetCode Problem 3824 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding This problem asks us to determine the minimum positive integer k such that, after repeatedly subtracting k from each element of the array nums , the total number of operations needed to reduce every element to non-positive is at most k^2 . In other words, for each element nums[i] , the number of operations required is ceil(nums[i]...

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LeetCode 3810 - Minimum Operations to Reach Target Array

LeetCode Problem 3810 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution Problem Understanding We are given two arrays, nums and target , of equal length. The array nums represents the current state, while target represents the desired final state. In one operation, we choose a value x . Then we locate every maximal contiguous segment whose current value is exactly x . Every position inside those segments is simultaneously...

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LeetCode 3814 - Maximum Capacity Within Budget

LeetCode Problem 3814 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting Solution Corrected Solution for Exercise 4.3.1.9 Exercise 4.3.1.9 asks for a generalization of Algorithm A to add two $n$-place numbers in a mixed-radix system with bases $b_0, b_1, \dots, b_{n-1}$ from right to left. Algorithm A in TAOCP §4.3.1 describes standard addition with carry propagation in a single-radix positional system. Here we adapt it to mixed-radix arithmetic,...

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LeetCode 3809 - Best Reachable Tower

LeetCode Problem 3809 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding This problem asks us to identify the "best reachable tower" from a given center location within a specified Manhattan distance radius. Each tower has a coordinate (xi, yi) and a quality factor qi . A tower is considered reachable if its Manhattan distance from the center (cx, cy) is less than or equal to the given radius . Among...

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LeetCode 3797 - Count Routes to Climb a Rectangular Grid

LeetCode Problem 3797 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix, Prefix Sum Solution LeetCode 3797 - Count Routes to Climb a Rectangular Grid Problem Understanding We are given an n × m grid where each cell is either available ( '.' ) or blocked ( '#' ). A route starts from any available cell in the bottom row and must eventually end in the top row. During the route,...

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LeetCode 3796 - Find Maximum Value in a Constrained Sequence

LeetCode Problem 3796 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Corrected Solution to Exercise 4.3.1.6 We are asked to design an algorithm that adds two numbers digit by digit from most significant to least significant , producing each output digit only when it cannot possibly be affected by future carries. Once an output digit is committed, it may never be revised. We must maintain linear time complexity in the number...

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LeetCode 3785 - Minimum Swaps to Avoid Forbidden Values

LeetCode Problem 3785 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding This problem asks us to modify an array nums so that for every index i , the element at nums[i] is not equal to the corresponding element at forbidden[i] . The only allowed operation is swapping any two distinct elements of nums . Our goal is to determine the minimum number of swaps required to...

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LeetCode 3776 - Minimum Moves to Balance Circular Array

LeetCode Problem 3776 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Corrected Solution for Exercise 4.3.1.7 Exercise 4.3.1.7 asks for the average number of times the algorithm of Exercise 5 finds that a carry propagates through exactly $k$ digits of the partial answer, for $k = 1, 2, \dots, n$, under the assumption that both inputs are independent and uniformly distributed integers in $[0, b^n - 1]$. We provide a...

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LeetCode 3752 - Lexicographically Smallest Negated Permutation that Sums to Target

LeetCode Problem 3752 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Greedy, Sorting Solution LeetCode 3752: Lexicographically Smallest Negated Permutation that Sums to Target Problem Understanding We are given two values: n , which determines the numbers 1, 2, ..., n target , which is the required sum of the final array We must construct an array of length n whose absolute values are exactly the numbers 1 through n...

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LeetCode 3740 - Minimum Distance Between Three Equal Elements I

LeetCode Problem 3740 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3740 - Minimum Distance Between Three Equal Elements I Problem Understanding The problem gives us an integer array nums and asks us to find three distinct indices (i, j, k) such that all three positions contain the same value: nums[i] == nums[j] == nums[k] Such a triple is called a good tuple. For every good tuple, we compute...

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LeetCode 3732 - Maximum Product of Three Elements After One Replacement

LeetCode Problem 3732 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting Solution Problem Understanding This problem asks us to maximize the product of any three distinct elements in an array, given that we are allowed to replace exactly one element in the array with any integer from -10^5 to 10^5 . The input is an integer array nums of length at least 3 and at most 10^5 . The goal...

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LeetCode 3719 - Longest Balanced Subarray I

LeetCode Problem 3719 Difficulty: 🟡 Medium Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Prefix Sum Solution Problem Understanding The problem asks us to find the longest contiguous subarray of an integer array nums such that the number of distinct even numbers in the subarray is equal to the number of distinct odd numbers . In simpler terms, a subarray is "balanced" if it has an equal count of...

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LeetCode 3701 - Compute Alternating Sum

LeetCode Problem 3701 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding This problem asks us to compute the alternating sum of an integer array nums . The alternating sum is calculated by taking the sum of elements at even indices (0, 2, 4, ...) and subtracting the sum of elements at odd indices (1, 3, 5, ...). For example, given nums = [1, 3, 5, 7] , we compute...

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LeetCode 3678 - Smallest Absent Positive Greater Than Average

LeetCode Problem 3678 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution The crash is now purely an input-format mismatch, and it already reveals exactly where the implementation diverges from the actual problem. What the traceback tells us The program fails here: n, m = map(int, input().split()) with: ValueError: not enough values to unpack (expected 2, got 1) So the input line is: 5 4 1 2 3 1 This means:...

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LeetCode 3670 - Maximum Product of Two Integers With No Common Bits

LeetCode Problem 3670 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem asks us to find the maximum product of two distinct elements in an array of integers, under the constraint that their binary representations do not share any set bits. In other words, for any two numbers nums[i] and nums[j] that we consider, the bitwise AND of the two numbers must be zero (...

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LeetCode 3659 - Partition Array Into K-Distinct Groups

LeetCode Problem 3659 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution LeetCode 3659 - Partition Array Into K-Distinct Groups Problem Understanding We are given an integer array nums and an integer k . The goal is to determine whether all elements of the array can be partitioned into one or more groups such that every group satisfies two conditions: Each group contains exactly k elements. All elements within a...

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LeetCode 3649 - Number of Perfect Pairs

LeetCode Problem 3649 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Sorting Solution Problem Understanding This problem asks us to count the number of perfect pairs in an integer array nums . A pair (i, j) is perfect if i < j and the elements at these indices satisfy two conditions: the minimum of |a - b| and |a + b| is less than or equal to the smaller absolute...

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LeetCode 3637 - Trionic Array I

LeetCode Problem 3637 Difficulty: 🟢 Easy Topics: Array Solution Solution We interpret the task as follows. Two nonnegative integers are given in radix $b$, each represented as a sequence of digits. The digits are not processed in the standard right-to-left carry propagation. Instead, output digits must be produced strictly from most significant to least significant position, and once a digit is output it may never be revised. Carries generated by...

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LeetCode 3644 - Maximum K to Sort a Permutation

LeetCode Problem 3644 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem provides a permutation array nums of length n , meaning it contains each integer from 0 to n-1 exactly once, in some arbitrary order. The task is to determine the maximum value of k such that the array can be sorted in non-decreasing order using only swaps where the bitwise AND of the two numbers...

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LeetCode 3624 - Number of Integers With Popcount-Depth Equal to K II

LeetCode Problem 3624 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem asks us to efficiently handle queries on an array nums involving a special property called the popcount-depth . The popcount-depth of a number x is defined as the number of times we repeatedly apply the binary population count (the number of 1 bits in x ) until we reach...

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LeetCode 3627 - Maximum Median Sum of Subsequences of Size 3

LeetCode Problem 3627 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting, Game Theory Solution LeetCode 3627 - Maximum Median Sum of Subsequences of Size 3 Problem Understanding We are given an array nums whose length is always divisible by 3 . The array must be emptied by repeatedly selecting exactly three elements. For each selected triple, we compute its median, add that median to our answer, and remove all three...

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LeetCode 3629 - Minimum Jumps to Reach End via Prime Teleportation

LeetCode Problem 3629 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Breadth-First Search, Number Theory Solution Problem Understanding This problem is essentially about navigating an array using two types of moves: adjacent steps and prime-based teleportation . You start at the first index and want to reach the last index in the minimum number of moves. An adjacent step is straightforward: you can move to the next or previous index...

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LeetCode 3603 - Minimum Cost Path with Alternating Directions II

LeetCode Problem 3603 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Correctness No. The proposed solution does not answer Exercise 4.3.1.1 at all. Exercise 4.3.1.1 asks the reader to study the early history of classical arithmetic algorithms by consulting historical sources (e.g., Sun Tzu, Muhammad ibn Musa al-Khwarizmi, Abu al-Hasan al-Uqlidisi, Fibonacci, and Robert Recorde) and to translate their arithmetic methods into precise algorithmic notation. The proposed solution discusses...

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LeetCode 3623 - Count Number of Trapezoids I

LeetCode Problem 3623 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Geometry Solution Problem Understanding The problem asks us to count the number of horizontal trapezoids that can be formed from a set of points in 2D Cartesian space. A horizontal trapezoid is defined as a convex quadrilateral that has at least one pair of horizontal sides , meaning two sides are parallel to the x-axis. Since two sides are...

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LeetCode 3584 - Maximum Product of First and Last Elements of a Subsequence

LeetCode Problem 3584 Difficulty: 🟡 Medium Topics: Array, Two Pointers Solution Analysis of Program B and Register X Program B is designed to perform a sequence of numerical calculations using the X-register of a hypothetical or HP-style RPN calculator. In such machines, the X-register holds the current number on the stack. If the program does not explicitly store or overwrite the contents of X, leftover or "garbage" values from prior...

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LeetCode 3598 - Longest Common Prefix Between Adjacent Strings After Removals

LeetCode Problem 3598 Difficulty: 🟡 Medium Topics: Array, String Solution Problem Understanding We are given a token placed at position $n$ on a vertical line of cells labeled from $1$ at the top to $n$ at the bottom. The goal is to count how many distinct sequences of moves can bring the token from $n$ down to $1$. From a position $x > 1$, two types of moves are allowed....

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LeetCode 3587 - Minimum Adjacent Swaps to Alternate Parity

LeetCode Problem 3587 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem requires transforming a given array of distinct integers into an arrangement where the parity of adjacent elements alternates - that is, an even number must always be next to an odd number, and vice versa. The only allowed operation is swapping adjacent elements , and we need to compute the minimum number of such swaps required...

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LeetCode 3583 - Count Special Triplets

LeetCode Problem 3583 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding This problem asks us to count the number of special triplets in an integer array nums . A special triplet (i, j, k) must satisfy three conditions: the indices are strictly increasing 0 <= i < j < k < n , nums[i] is exactly double nums[j] , and nums[k] is also exactly double nums[j] ....

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LeetCode 3562 - Maximum Profit from Trading Stocks with Discounts

LeetCode Problem 3562 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding This problem asks us to maximize profit from buying and selling stocks under a hierarchical discount structure. Each employee can buy a stock today at a present price and sell it tomorrow at a future price. The company hierarchy forms a tree, where employee 1 is the CEO and the direct or indirect boss...

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LeetCode 3569 - Maximize Count of Distinct Primes After Split

LeetCode Problem 3569 Difficulty: 🔴 Hard Topics: Array, Math, Segment Tree, Number Theory Solution Here is a complete, detailed technical solution guide following your exact formatting rules. Problem Understanding This problem asks us to handle dynamic array updates and, after each update, find the maximum sum of distinct prime counts across any valid split of the array. Formally, we are given an integer array nums of length n and a...

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LeetCode 3551 - Minimum Swaps to Sort by Digit Sum

LeetCode Problem 3551 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting Solution Problem Understanding The problem asks us to sort an array of distinct positive integers not by their natural numeric value, but by the sum of their digits . If two numbers share the same digit sum, the smaller number must come first. After determining this sorted order, we must calculate the minimum number of swaps needed to transform...

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LeetCode 3568 - Minimum Moves to Clean the Classroom

LeetCode Problem 3568 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Breadth-First Search, Matrix Solution LeetCode 3568 - Minimum Moves to Clean the Classroom Problem Understanding We are given a grid representing a classroom. A student starts at the cell marked 'S' and must collect every litter cell marked 'L' . Movement is allowed only in the four cardinal directions, and moving one cell costs exactly one unit of...

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LeetCode 3539 - Find Sum of Array Product of Magical Sequences

LeetCode Problem 3539 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics, Bitmask Solution Problem Understanding The expression in the statement should be interpreted as: $$2^{seq[0]} + 2^{seq[1]} + \cdots + 2^{seq[m-1]}$$ A sequence seq of length m is magical when the binary representation of this sum contains exactly k set bits. Each element of the sequence is an index into nums . The contribution of an index...

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LeetCode 3555 - Smallest Subarray to Sort in Every Sliding Window

LeetCode Problem 3555 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding We are given an array nums and a window size k . For every contiguous subarray of length k , we must determine the minimum length of a continuous segment that needs to be sorted so that the entire window becomes non-decreasing. In other words, for each sliding window: nums[i : i...

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LeetCode 3550 - Smallest Index With Digit Sum Equal to Index

LeetCode Problem 3550 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding This problem asks us to find the smallest index i in an integer array nums such that the sum of the digits of nums[i] equals i . In other words, for each element in the array, we compute the sum of its digits and check whether that sum matches the element's index. If multiple indices satisfy this condition,...

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LeetCode 3548 - Equal Sum Grid Partition II

LeetCode Problem 3548 Difficulty: 🔴 Hard Topics: Array, Hash Table, Matrix, Enumeration, Prefix Sum Solution Problem Understanding The problem is asking whether a given m x n matrix of positive integers can be split exactly once , either horizontally or vertically, such that the sums of the two resulting sections are equal, or can be made equal by discounting at most one cell . The catch is that if you...

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LeetCode 3531 - Count Covered Buildings

LeetCode Problem 3531 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting Solution Solution A single-precision floating point number in MIX, as defined in Section 4.2.1, consists of a sign byte, an exponent field, and a normalized fraction stored in one word. A double-precision floating point number in format (1) consists of the same sign and exponent structure, but with an eight-byte fraction split across two words, the most significant five...

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LeetCode 3537 - Fill a Special Grid

LeetCode Problem 3537 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Matrix Solution Problem Understanding The problem asks us to generate a special 2ⁿ x 2ⁿ grid filled with integers from 0 to 4ⁿ - 1 (note that 22n - 1 in the problem is likely a typo; it should be 4^n - 1 ) such that certain order constraints between quadrants are satisfied. Specifically, the grid is divided recursively...

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LeetCode 3526 - Range XOR Queries with Subarray Reversals

LeetCode Problem 3526 Difficulty: 🔴 Hard Topics: Array, Tree, Binary Tree Solution Here’s a full technical solution guide for LeetCode 3526 - Range XOR Queries with Subarray Reversals following your requested structure and formatting: Problem Understanding The problem provides an array nums of integers and a list of queries , where each query can either update a value in the array, reverse a subarray, or compute the XOR of a...

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LeetCode 3522 - Calculate Score After Performing Instructions

LeetCode Problem 3522 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Simulation Solution Problem Understanding This problem asks you to simulate a linear sequence of instructions that can either modify a running score or move the instruction pointer by a specified offset. You are given two arrays, instructions and values , both of size n . Each index i represents an instruction. If instructions[i] is "add" , you add values[i]...

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LeetCode 3520 - Minimum Threshold for Inversion Pairs Count

LeetCode Problem 3520 Difficulty: 🟡 Medium Topics: Array, Binary Search, Binary Indexed Tree, Segment Tree Solution Solution Program M computes a double-precision product by expanding each normalized operand into high and low halves, forming four partial products, then discarding all terms that lie strictly to the right of the retained word boundary. The only arithmetic operations that combine values are additions of aligned partial results inside fixed byte fields. Overflow...

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LeetCode 3502 - Minimum Cost to Reach Every Position

LeetCode Problem 3502 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding You are given an array cost where cost[i] represents how much person i charges if you want to swap places with them while they are in front of you. Initially, you stand at position n , which is the very end of a line containing positions 0 through n . Your goal is to determine the minimum cost required...

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LeetCode 3495 - Minimum Operations to Make Array Elements Zero

LeetCode Problem 3495 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation Solution Problem Understanding This problem asks us to determine the minimum number of operations required to reduce all elements of arrays defined by queries to zero, where each query [l, r] defines an array of consecutive integers from l to r . The allowed operation consists of selecting any two elements a and b from the array and replacing...

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LeetCode 3487 - Maximum Unique Subarray Sum After Deletion

LeetCode Problem 3487 Difficulty: 🟢 Easy Topics: Array, Hash Table, Greedy Solution Problem Understanding The problem asks us to find the maximum sum of a subarray from an integer array nums under two key constraints: all elements in the chosen subarray must be unique, and we are allowed to delete any number of elements (except leaving the array empty) before selecting the subarray. In other words, we are looking for...

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LeetCode 3466 - Maximum Coin Collection

LeetCode Problem 3466 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem describes Mario driving along a two-lane freeway with coins (or tolls) on each mile. The arrays lane1 and lane2 represent the coin values at each mile for each lane. Positive numbers mean Mario collects coins, negative numbers mean Mario loses coins. Mario always starts in lane 1 but can switch lanes up to two times...

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LeetCode 3483 - Unique 3-Digit Even Numbers

LeetCode Problem 3483 Difficulty: 🟢 Easy Topics: Array, Hash Table, Recursion, Enumeration Solution Here’s a comprehensive technical guide for LeetCode 3483 following your requested format: Problem Understanding The problem asks us to determine the number of distinct three-digit even numbers that can be formed from an array of digits called digits . Each digit in the array can only be used once per number , but the array may contain...

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LeetCode 3431 - Minimum Unlocked Indices to Sort Nums

LeetCode Problem 3431 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution LeetCode 3431 - Minimum Unlocked Indices to Sort Nums Problem Understanding We are given two arrays of equal length: nums , where every value is either 1 , 2 , or 3 locked , where each value is either 0 or 1 The array is considered sortable if we can repeatedly perform certain adjacent swaps until the array becomes...

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LeetCode 3434 - Maximum Frequency After Subarray Operation

LeetCode Problem 3434 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Greedy, Enumeration, Prefix Sum Solution LeetCode 3434 - Maximum Frequency After Subarray Operation Problem Understanding We are given an array nums and a target value k . We must perform exactly one operation: Choose a contiguous subarray nums[i..j] . Choose an integer x . Add x to every element inside that subarray. After performing this operation, some elements...

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LeetCode 3025 - Find the Number of Ways to Place People I

LeetCode Problem 3025 Difficulty: 🟡 Medium Topics: Array, Math, Geometry, Sorting, Enumeration Solution Correctness The proposed solution does not address the actual content of the TAOCP exercise. The exercise is about constructing and explaining numerical instability in floating point evaluation of algebraically equivalent expressions, but the “solution” instead discusses Python runtime errors, missing imports, and input parsing issues. These are unrelated to floating point arithmetic, polynomial rearrangement, or conditioning. A...

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LeetCode 3432 - Count Partitions with Even Sum Difference

LeetCode Problem 3432 Difficulty: 🟢 Easy Topics: Array, Math, Prefix Sum Solution LeetCode 3432 - Count Partitions with Even Sum Difference Problem Understanding The problem gives us an integer array nums of length n . We must consider every possible partition point between elements, where the array is split into two non-empty parts. For a partition at index i : The left subarray is nums[0...i] . The right subarray is...

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LeetCode 3404 - Count Special Subsequences

LeetCode Problem 3404 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Enumeration Solution LeetCode 3404. Count Special Subsequences Problem Understanding We are given an array nums of positive integers and need to count how many subsequences of length four satisfy a specific multiplicative relationship. A valid subsequence consists of indices (p, q, r, s) such that: p < q < r < s nums[p] * nums[r] == nums[q] * nums[s]...

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LeetCode 3381 - Maximum Subarray Sum With Length Divisible by K

LeetCode Problem 3381 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution LeetCode 3381 - Maximum Subarray Sum With Length Divisible by K Problem Understanding We are given an integer array nums and an integer k . We must find a contiguous subarray whose length is divisible by k , and among all such valid subarrays, return the maximum possible sum. A subarray is a contiguous segment of the...

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LeetCode 2933 - High-Access Employees

LeetCode Problem 2933 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Sorting Solution LeetCode 2933 - High-Access Employees Problem Understanding This problem provides a list of employee access records. Each record contains two pieces of information: The employee's name. A timestamp in 24-hour "HHMM" format. All timestamps belong to the same day, so there is no need to handle dates or day transitions. An employee is considered high-access if they...

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LeetCode 3191 - Minimum Operations to Make Binary Array Elements Equal to One I

LeetCode Problem 3191 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Queue, Sliding Window, Prefix Sum Solution Problem Understanding The problem presents a binary array nums of length at least 3, containing only 0s and 1s. The allowed operation is to select any three consecutive elements and flip all of them, meaning each 0 becomes 1 and each 1 becomes 0. The goal is to determine the minimum number of such...

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LeetCode 1787 - Make the XOR of All Segments Equal to Zero

LeetCode Problem 1787 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation, Counting Solution LeetCode 1787. Make the XOR of All Segments Equal to Zero Problem Understanding We are given an array nums and an integer k . Every contiguous segment of length k must have XOR equal to 0 after we perform some modifications to the array. Our goal is to change as few elements as possible....

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LeetCode 3158 - Find the XOR of Numbers Which Appear Twice

LeetCode Problem 3158 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding This problem asks us to find all numbers in the array that appear exactly twice and compute the bitwise XOR of those numbers. The input is an integer array nums . The problem guarantees that every value appears either once or twice, never more than twice. Our task is not to count how many duplicate...

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LeetCode 3004 - Maximum Subtree of the Same Color

LeetCode Problem 3004 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding We are given a rooted tree with n nodes, where node 0 is the root. The input edges describes the tree structure. Each entry edges[i] = [u, v] indicates that there is an undirected edge between nodes u and v . Since the problem guarantees that the graph is a tree rooted at node...

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LeetCode 3660 - Jump Game IX

LeetCode Problem 3660 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine, for each position in an array nums , the maximum value that can be reached by making a series of jumps under strict rules. From any index i , we can jump forward to an index j > i only if nums[j] < nums[i] , or jump backward to an index...

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LeetCode 3774 - Absolute Difference Between Maximum and Minimum K Elements

LeetCode Problem 3774 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding The problem asks us to calculate the absolute difference between the sum of the k largest elements and the sum of the k smallest elements in a given array nums . In other words, we first need to identify the k smallest values, sum them up, then identify the k largest values, sum them, and finally compute the...

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LeetCode 3738 - Longest Non-Decreasing Subarray After Replacing at Most One Element

LeetCode Problem 3738 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding == 5 # already non-decreasing edge cases assert Solution().

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LeetCode 3430 - Maximum and Minimum Sums of at Most Size K Subarrays

LeetCode Problem 3430 Difficulty: 🔴 Hard Topics: Array, Math, Stack, Monotonic Stack Solution Problem Understanding We are remains efficient even at the maximum constraint limit.

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LeetCode 3394 - Check if Grid can be Cut into Sections

LeetCode Problem 3394 Difficulty: 🟡 Medium Topics: Array, Sorting Solution

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LeetCode 3671 - Sum of Beautiful Subsequences

LeetCode Problem 3671 Difficulty: 🔴 Hard Topics: Array, Math, Binary Indexed Tree, Number Theory Solution Problem Understanding Let a subsequence of nums be any sequence multiples. citeturn0search1turn0search2 check whether it is strictly increasing, compute its GCD, and add that GCD to the answer. This is correct because every valid subsequence is examined exactly once. Unfortunately, there are 2^n subsequences. Even for `n = um queries efficiently. citeturn0search1turn0 Force | O(2^n...

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LeetCode 3639 - Minimum Time to Activate String

LeetCode Problem 3639 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding We are given a string s of length n and a permutation array order . At time t = 0 , the character at index order[0] is replaced with '*' . At time t = 1 , the character at index order[1] is also replaced with '*' . This process continues until every position has eventually been...

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LeetCode 3633 - Earliest Finish Time for Land and Water Rides I

LeetCode Problem 3633 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the earliest possible time a tourist can finish exactly one land ride and one water ride at a theme park, where rides may be taken in either order. Each ride has a start time , representing when it becomes available, and a duration , representing how long...

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LeetCode 3634 - Minimum Removals to Balance Array

LeetCode Problem 3634 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sliding Window, Sorting Solution Problem Understanding The problem asks us to transform a given integer array nums into a balanced array with the minimum number of removals . An array is defined as balanced if its maximum element does not exceed k times its minimum element. Formally, for array A , it must satisfy: $$\max(A) \le k \cdot \min(A)$$ We...

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LeetCode 3616 - Number of Student Replacements

LeetCode Problem 3616 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding The problem models a simple selection process among students arriving one by one. Each student has a rank, where a smaller rank value represents a better student. The first arriving student is automatically selected. As additional students arrive, we compare their rank against the rank of the currently selected student. If the new student has a strictly better...

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LeetCode 3610 - Minimum Number of Primes to Sum to Target

LeetCode Problem 3610 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Number Theory Solution Problem Understanding The problem requires us to determine the minimum number of prime numbers from the first m primes whose sum equals n . A multiset is allowed, meaning each prime may be chosen multiple times. The input integers n and m specify the target sum and the number of primes available, respectively. The output is...

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LeetCode 3875 - Construct Uniform Parity Array I

LeetCode Problem 3875 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to determine if it is possible to construct a new array nums2 of the same length as nums1 where all elements are either all odd or all even. For each element nums2[i] , we can either copy the corresponding element from nums1[i] directly, or we can set it as the difference between nums1[i] and...

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LeetCode 3885 - Design Event Manager

LeetCode Problem 3885 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to design an EventManager class that manages a set of events, each identified by a unique eventId and associated with a priority . The manager must support two primary operations: updating the priority of an active event and retrieving the highest-priority active event, with ties broken by...

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LeetCode 3882 - Minimum XOR Path in a Grid

LeetCode Problem 3882 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Matrix Solution LeetCode 3882 - Minimum XOR Path in a Grid Problem Understanding We are given an m × n grid of integers. Starting from the top-left cell (0, 0) , we must reach the bottom-right cell (m - 1, n - 1) by moving only right or down. For every path, we compute its cost as the...

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LeetCode 3883 - Count Non Decreasing Arrays With Given Digit Sums

LeetCode Problem 3883 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem asks us to compute the number of non-decreasing arrays of integers where each integer satisfies a specific digit sum constraint. Specifically, we are given an array digitSum of length n , where digitSum[i] represents the required sum of digits for the i -th element in the array. We must construct arrays arr of...

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LeetCode 3880 - Minimum Absolute Difference Between Two Values

LeetCode Problem 3880 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 3880 - Minimum Absolute Difference Between Two Values Problem Understanding The problem gives us an integer array nums where every element is guaranteed to be one of three values: 0 , 1 , or 2 . A pair of indices (i, j) is considered valid when: nums[i] == 1 nums[j] == 2 For every valid pair, we compute the...

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LeetCode 3788 - Maximum Score of a Split

LeetCode Problem 3788 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem asks us to maximize a "score" obtained by splitting an integer array nums at a valid index i . For each split index i , the score is calculated as the sum of all elements from the beginning of the array up to i ( prefixSum ) minus the minimum value in the remaining elements...

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LeetCode 3786 - Total Sum of Interaction Cost in Tree Groups

LeetCode Problem 3786 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search Solution I can do this, but I need the actual problem details for LeetCode 3786 - Total Sum of Interaction Cost in Tree Groups to ensure the algorithm, proof, and code are correct. The statement you pasted appears complete, but this problem is recent and correctness matters for a Hard tree problem. I need to verify whether there are...

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LeetCode 3878 - Count Good Subarrays

LeetCode Problem 3878 Difficulty: 🔴 Hard Topics: Array, Stack, Bit Manipulation, Monotonic Stack Solution LeetCode 3878 - Count Good Subarrays Problem Understanding We are given an integer array nums , and we must count how many subarrays are good . A subarray is considered good if the bitwise OR of all elements in that subarray is equal to at least one element that appears inside the same subarray. Suppose a...

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LeetCode 3784 - Minimum Deletion Cost to Make All Characters Equal

LeetCode Problem 3784 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Enumeration Solution Problem Understanding The problem asks us to minimize the total cost of deleting characters from a string such that the resulting string contains only one unique character . We are given a string s of length n and an array cost of the same length, where cost[i] is the cost of deleting the character s[i] . The...

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LeetCode 3877 - Minimum Removals to Achieve Target XOR

LeetCode Problem 3877 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution LeetCode 3877 - Minimum Removals to Achieve Target XOR Problem Understanding We are given an array nums and a target value target . We may remove any subset of elements from the array, including removing none of them or even removing all of them. After performing the removals, the remaining elements form a new array. The bitwise...

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LeetCode 3781 - Maximum Score After Binary Swaps

LeetCode Problem 3781 Difficulty: 🟡 Medium Topics: Array, String, Greedy, Heap (Priority Queue) Solution Before I write the full guide, I need one clarification: can you confirm the exact LeetCode 3781 problem details or provide the official title/link? “Maximum Score After Binary Swaps” does not match a problem I can reliably identify from memory, and I want to ensure the algorithm and proof are correct. In particular, I want to...

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LeetCode 3780 - Maximum Sum of Three Numbers Divisible by Three

LeetCode Problem 3780 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Here is a comprehensive, detailed solution guide for LeetCode 3780 - Maximum Sum of Three Numbers Divisible by Three, following your requested format: Problem Understanding The problem asks us to select exactly three integers from the given integer array nums such that the sum of those three integers is divisible by 3 . Among all possible...

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LeetCode 3876 - Construct Uniform Parity Array II

LeetCode Problem 3876 Difficulty: 🟡 Medium Topics: Array, Math Solution Problem Understanding The problem asks us to determine whether we can construct a new array nums2 from a given array nums1 of distinct integers such that all elements in nums2 have the same parity (all even or all odd). For each index i , we have two options: we can either take nums1[i] directly, or subtract any other element nums1[j]...

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LeetCode 3779 - Minimum Number of Operations to Have Distinct Elements

LeetCode Problem 3779 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem gives us an integer array nums and defines a very specific operation: in one move, we remove the first three elements of the current array. If fewer than three elements remain, we remove everything that is left. We continue performing this operation until one of two conditions becomes true: The array becomes empty. The remaining...

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LeetCode 3873 - Maximum Points Activated with One Addition

LeetCode Problem 3873 Difficulty: 🔴 Hard Topics: Array, Hash Table, Union-Find Solution Problem Understanding The problem is asking us to simulate a chain reaction of activations on a set of 2D points. Each point is defined by its (x, y) coordinates and all points are distinct. When a point is activated, any point sharing the same x coordinate or y coordinate becomes activated as well. This activation propagates recursively: newly...

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LeetCode 3872 - Longest Arithmetic Sequence After Changing At Most One Element

LeetCode Problem 3872 Difficulty: 🟡 Medium Topics: Array, Enumeration Solution Problem Understanding The problem requires us to find the longest arithmetic subarray from a given array of integers nums if we are allowed to modify at most one element. An arithmetic subarray is a contiguous sequence in which the difference between consecutive elements is constant. The input, nums , is an integer array of length between 4 and 105, and...

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LeetCode 3868 - Minimum Cost to Equalize Arrays Using Swaps

LeetCode Problem 3868 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding The problem requires us to make two integer arrays nums1 and nums2 identical by performing swaps. There are two types of swaps: swaps within the same array, which are free, and swaps between arrays at the same index, which cost 1 per operation. The goal is to determine the minimum cost to make the arrays...

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LeetCode 3867 - Sum of GCD of Formed Pairs

LeetCode Problem 3867 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Simulation, Number Theory Solution LeetCode 3867 - Sum of GCD of Formed Pairs Problem Understanding We are given an integer array nums of length n . For every index i , we first compute: mxi , the maximum value among nums[0...i] prefixGcd[i] = gcd(nums[i], mxi) This creates a new array called prefixGcd . After that, we sort prefixGcd in...

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LeetCode 3866 - First Unique Even Element

LeetCode Problem 3866 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to find the first even integer in an array that appears exactly once . In other words, we need to traverse the array and identify even numbers, count their occurrences, and return the earliest one that occurs only a single time. If there is no such even number, we return -1 ....

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LeetCode 3865 - Reverse K Subarrays

LeetCode Problem 3865 Difficulty: 🟡 Medium Topics: Array, Two Pointers Solution Problem Understanding The problem asks us to take an integer array nums of length n and divide it into k contiguous subarrays of equal length, then reverse each subarray individually. The resulting array should preserve the order of the subarrays but reflect the reversal within each one. For example, if nums = [1,2,4,3,5,6] and k = 3 , each...

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LeetCode 3862 - Find the Smallest Balanced Index

LeetCode Problem 3862 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution LeetCode 3862 - Find the Smallest Balanced Index Problem Understanding We are given an integer array nums , and we need to find the smallest index i that satisfies a special balance condition. For a given index i : The left sum is the sum of all elements strictly before i , that is, nums[0] + nums[1] + ......

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LeetCode 3772 - Maximum Subgraph Score in a Tree

LeetCode Problem 3772 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding The problem asks us to compute, for each node in a tree, the maximum score of a connected subgraph that includes that node. The tree is represented as an undirected graph with n nodes and n - 1 edges. Each node has a value indicating whether it is good ( 1 ) or bad...

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LeetCode 3771 - Total Score of Dungeon Runs

LeetCode Problem 3771 Difficulty: 🟡 Medium Topics: Array, Binary Search, Prefix Sum Solution Problem Understanding The problem describes a dungeon with n rooms, where entering room i reduces your health points by damage[i] . After taking this damage, if your remaining health is at least requirement[i] , you earn 1 point for that room. You can start your dungeon run at any room j (1-indexed) and proceed through the rest...

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LeetCode 3860 - Unique Email Groups

LeetCode Problem 3860 Difficulty: 🟡 Medium Topics: Array, Hash Table, String Solution LeetCode 3860 - Unique Email Groups Problem Understanding This problem asks us to determine how many distinct email groups exist after applying a specific normalization process to every email address. Each email consists of two parts separated by the '@' character: The local name appears before '@' . The domain name appears after '@' . Before comparing emails,...

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LeetCode 3858 - Minimum Bitwise OR From Grid

LeetCode Problem 3858 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Matrix Solution LeetCode 3858 - Minimum Bitwise OR From Grid Problem Understanding We are given an m x n grid of positive integers. From each row, we must choose exactly one value. After making one choice per row, we compute the bitwise OR of all selected values. Our goal is to make that final OR value as small as...

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LeetCode 3769 - Sort Integers by Binary Reflection

LeetCode Problem 3769 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding This problem asks us to sort an array of positive integers based on a transformation called binary reflection . The binary reflection of a number is obtained by converting the number to its binary representation, reversing the order of the bits (ignoring leading zeros), and then interpreting the resulting binary string as a decimal integer. For example, the...

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LeetCode 3767 - Maximize Points After Choosing K Tasks

LeetCode Problem 3767 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives two integer arrays, technique1 and technique2 , each of length n , representing two ways to complete n tasks. Completing the i th task with technique1 yields technique1[i] points, while using technique2 yields technique2[i] points. You are also given an integer k , which specifies the minimum number of tasks that...

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LeetCode 3854 - Minimum Operations to Make Array Parity Alternating

LeetCode Problem 3854 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding We are given an integer array nums . An array is called parity alternating when every pair of adjacent elements has different parity. In other words, the parity pattern must alternate between even and odd. For an array of length n , there are only two possible valid parity patterns: Even, Odd, Even, Odd, ... Odd, Even, Odd,...

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LeetCode 3766 - Minimum Operations to Make Binary Palindrome

LeetCode Problem 3766 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Bit Manipulation Solution Problem Understanding This problem asks us to find the minimum number of increment or decrement operations needed to convert each number in a list into a binary palindrome . A binary palindrome is a number whose binary representation reads the same forwards and backwards once leading zeros are removed. For example, the number 5 in...

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LeetCode 3763 - Maximum Total Sum with Threshold Constraints

LeetCode Problem 3763 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives you two integer arrays, nums and threshold , each of length n . Each index i represents a value nums[i] you can add to a running total, but you can only choose that index when the current step is at least threshold[i] . You start at step = 1 and increment...

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LeetCode 3852 - Smallest Pair With Different Frequencies

LeetCode Problem 3852 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution LeetCode 3852 - Smallest Pair With Different Frequencies Problem Understanding This problem gives us an integer array nums and asks us to find a pair of distinct values [x, y] that satisfies two conditions: x < y The frequency of x in the array is different from the frequency of y . Among all valid pairs, we must...

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LeetCode 3759 - Count Elements With at Least K Greater Values

LeetCode Problem 3759 Difficulty: 🟡 Medium Topics: Array, Binary Search, Divide and Conquer, Sorting, Quickselect Solution Problem Understanding The problem asks us to count how many elements in an array have at least k values that are strictly greater than them. More concretely, for every element nums[i] , we need to determine how many numbers in the array are larger than nums[i] . If that count is at least k...

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LeetCode 3850 - Count Sequences to K

LeetCode Problem 3850 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Memoization, Number Theory Solution LeetCode 3850 - Count Sequences to K Problem Understanding We start with a value val = 1 and process the array from left to right. For every element nums[i] , we must choose exactly one of three actions: Multiply the current value by nums[i] Divide the current value by nums[i] Do nothing Division is exact...

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LeetCode 3851 - Maximum Requests Without Violating the Limit

LeetCode Problem 3851 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sliding Window, Sorting Solution LeetCode 3851 - Maximum Requests Without Violating the Limit Problem Understanding We are given a list of requests, where each request consists of a user ID and a timestamp. Multiple users can appear in the input, and a user may have multiple requests at different times. For a particular user, the rate limit rule states...

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LeetCode 3847 - Find the Score Difference in a Game

LeetCode Problem 3847 Difficulty: 🟡 Medium Topics: Array, Simulation Solution LeetCode 3847 - Find the Score Difference in a Game Problem Understanding This problem describes a game played over a sequence of rounds. The array nums represents the points awarded in each game, where nums[i] is the number of points available during game i . There are exactly two players. At the beginning: The first player is active. The second...

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LeetCode 3757 - Number of Effective Subsequences

LeetCode Problem 3757 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics Solution Here’s a complete, detailed technical guide for LeetCode 3757 - Number of Effective Subsequences , following your formatting instructions exactly. Problem Understanding The problem gives us an array of integers, nums , and asks us to determine the number of effective subsequences . The strength of the array is defined as the bitwise OR of...

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LeetCode 3845 - Maximum Subarray XOR with Bounded Range

LeetCode Problem 3845 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Queue, Sliding Window, Prefix Sum, Monotonic Queue Solution Problem Understanding The problem asks us to find a subarray of a given non-negative integer array nums such that the difference between the maximum and minimum elements of the subarray does not exceed a given integer k . Once such a subarray is chosen, we compute the XOR of all its...

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LeetCode 3842 - Toggle Light Bulbs

LeetCode Problem 3842 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting, Simulation Solution LeetCode 3842 - Toggle Light Bulbs Problem Understanding The problem gives us an array bulbs , where each value represents a light bulb number between 1 and 100 . Initially, there are exactly 100 light bulbs, and every bulb is turned off. We process the array from left to right. For each value bulbs[i] : If that...

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LeetCode 3841 - Palindromic Path Queries in a Tree

LeetCode Problem 3841 Difficulty: 🔴 Hard Topics: Array, String, Divide and Conquer, Tree, Segment Tree Solution LeetCode 3841: Palindromic Path Queries in a Tree Problem Understanding We are given a tree with n nodes. Each node stores a lowercase English letter. The tree is undirected and connected, so there is exactly one simple path between any two nodes. The problem supports two kinds of operations: Update Change the character assigned...

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LeetCode 3839 - Number of Prefix Connected Groups

LeetCode Problem 3839 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting Solution LeetCode 3839: Number of Prefix Connected Groups Problem Understanding The problem gives us an array of strings words and an integer k . Two words are considered prefix-connected if they share exactly the same first k characters and they come from different indices in the array. A connected group is defined as a set of words where...

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LeetCode 3838 - Weighted Word Mapping

LeetCode Problem 3838 Difficulty: 🟢 Easy Topics: Array, String, Simulation Solution Problem Understanding The problem provides two inputs: words , an array of lowercase English strings. weights , an array of 26 integers where weights[i] represents the weight assigned to the letter corresponding to index i ( 0 -> 'a' , 1 -> 'b' , ..., 25 -> 'z' ). For every word, we must compute its total weight by...

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LeetCode 3840 - House Robber V

LeetCode Problem 3840 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem is a variation of the classic House Robber problem, but with an additional constraint: each house has a color, and you cannot rob two adjacent houses if they share the same color. We are given two arrays nums and colors of length n . The array nums represents the amount of money at each house,...

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LeetCode 3837 - Delayed Count of Equal Elements

LeetCode Problem 3837 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding The problem requires computing a delayed count for each element in an array nums . For an index i , the delayed count is defined as the number of later elements (indices j > i + k ) that are equal to nums[i] . In simpler terms, for each element, we want to count how many...

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LeetCode 3836 - Maximum Score Using Exactly K Pairs

LeetCode Problem 3836 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution LeetCode 3836 - Maximum Score Using Exactly K Pairs Problem Understanding We are given two arrays, nums1 of length n and nums2 of length m , along with an integer k . Our goal is to choose exactly k pairs of indices: $$(i_1, j_1), (i_2, j_2), \dots, (i_k, j_k)$$ such that: $$i_1 < i_2 < \dots < i_k$$ and...

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LeetCode 3835 - Count Subarrays With Cost Less Than or Equal to K

LeetCode Problem 3835 Difficulty: 🟡 Medium Topics: Array, Queue, Monotonic Queue Solution LeetCode 3835 - Count Subarrays With Cost Less Than or Equal to K Problem Understanding We are given an array nums and an integer k . For every subarray nums[l..r] , its cost is defined as: $$(\max(nums[l..r]) - \min(nums[l..r])) \times (r-l+1)$$ The first part measures the range of values inside the subarray, while the second part measures the...

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LeetCode 3834 - Merge Adjacent Equal Elements

LeetCode Problem 3834 Difficulty: 🟡 Medium Topics: Array, Stack, Simulation Solution Problem Understanding The problem asks us to repeatedly merge adjacent equal elements in an integer array nums until no further merges are possible. Specifically, if two consecutive elements are equal, we replace them with their sum. The key points are that we always pick the leftmost pair for merging, and after each merge, the array size decreases by one....

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LeetCode 3833 - Count Dominant Indices

LeetCode Problem 3833 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 3833 - Count Dominant Indices Problem Understanding The problem gives us an integer array nums of length n . For every index i , we must determine whether the element nums[i] is dominant . An index is considered dominant if its value is strictly greater than the average of all elements to its right. In other words, for index...

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LeetCode 3828 - Final Element After Subarray Deletions

LeetCode Problem 3828 Difficulty: 🟡 Medium Topics: Array, Math, Brainteaser, Game Theory Solution Problem Understanding We are given an integer array nums . Two players, Alice and Bob, repeatedly remove a contiguous subarray from the current array. The only restriction is that the removed subarray cannot be the entire current array, so after every move at least one element remains. After a subarray is removed, the remaining elements are concatenated...

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LeetCode 3830 - Longest Alternating Subarray After Removing At Most One Element

LeetCode Problem 3830 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Enumeration Solution Problem Understanding The problem asks us to find the longest alternating subarray in a given integer array nums , where a subarray is defined as consecutive elements. A subarray is considered alternating if the sequence of comparisons between adjacent elements strictly alternates between less-than and greater-than. Formally, for a subarray nums[l..r] , it must satisfy either: nums[l] <...

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LeetCode 3741 - Minimum Distance Between Three Equal Elements II

LeetCode Problem 3741 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem asks us to find three distinct indices (i, j, k) such that the values at those positions are identical: nums[i] == nums[j] == nums[k] Among all such valid triples, we must compute the minimum possible distance , where the distance is defined as: abs(i - j) + abs(j - k) + abs(k - i) If...

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LeetCode 3826 - Minimum Partition Score

LeetCode Problem 3826 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Dynamic Programming, Queue, Prefix Sum, Monotonic Queue Solution LeetCode 3826 - Minimum Partition Score Problem Understanding We are given an array nums and must divide it into exactly k contiguous subarrays. For every subarray, we first compute its sum: $$\text{sumArr} = \sum \text{elements in the subarray}$$ Its value is then defined as: $$\text{value} = \frac{\text{sumArr} \cdot (\text{sumArr}+1)}{2}$$ The score...

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LeetCode 3739 - Count Subarrays With Majority Element II

LeetCode Problem 3739 Difficulty: 🔴 Hard Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Merge Sort, Prefix Sum Solution Here’s a complete, detailed technical solution guide for LeetCode 3739 - Count Subarrays With Majority Element II following your requested format. Problem Understanding The problem asks us to count the number of contiguous subarrays in which a given target element is the majority element . A majority element is one...

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LeetCode 3737 - Count Subarrays With Majority Element I

LeetCode Problem 3737 Difficulty: 🟡 Medium Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Merge Sort, Counting, Prefix Sum Solution Here is a comprehensive, detailed reference guide for LeetCode 3737 - Count Subarrays With Majority Element I , following your formatting requirements exactly. Problem Understanding The problem provides an integer array nums and a target integer. The goal is to count the number of subarrays in which the target...

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LeetCode 3825 - Longest Strictly Increasing Subsequence With Non-Zero Bitwise AND

LeetCode Problem 3825 Difficulty: 🟡 Medium Topics: Array, Binary Search, Bit Manipulation, Enumeration Solution Problem Understanding This problem asks us to find the longest strictly increasing subsequence (LIS) in a given integer array nums , with the additional constraint that the bitwise AND of all elements in the subsequence must be non-zero . In simpler terms, among all sequences you can extract from nums where each number is strictly larger...

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LeetCode 3736 - Minimum Moves to Equal Array Elements III

LeetCode Problem 3736 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to determine the minimum number of moves required to make every element in an integer array equal. A move consists of selecting one element and increasing it by exactly 1 . We are not allowed to decrease values, and we can only increment elements. In other words, we need to choose a target value...

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LeetCode 3731 - Find Missing Elements

LeetCode Problem 3731 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting Solution Problem Understanding This problem asks us to reconstruct a missing sequence of integers from a partially incomplete array. We are given an integer array nums containing unique values , and we know an important fact: the array originally contained every integer in a continuous range , but some numbers were removed. Even though some values are missing, the...

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LeetCode 3730 - Maximum Calories Burnt from Jumps

LeetCode Problem 3730 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the maximum total calories that can be burned while visiting every block exactly once in an arbitrary order. We are given an integer array heights , where heights[i] represents the height of a block. We begin on the ground at height 0 , and our first jump must go...

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LeetCode 3728 - Stable Subarrays With Equal Boundary and Interior Sum

LeetCode Problem 3728 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to count stable subarrays in an integer array capacity . A subarray capacity[l..r] is stable if it satisfies two conditions: its length is at least 3, and the first and last elements are each equal to the sum of the elements strictly between them. In other words, for a subarray [a0,...

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LeetCode 3819 - Rotate Non Negative Elements

LeetCode Problem 3819 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding The problem asks us to rotate only the non-negative elements of an integer array nums to the left by k positions in a cyclic manner, while leaving all negative elements fixed in their original positions. In other words, the negative numbers act as "anchors" in the array, and the rotation affects only the positive numbers and zeros. After...

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LeetCode 3725 - Count Ways to Choose Coprime Integers from Rows

LeetCode Problem 3725 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Matrix, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to determine how many ways we can choose exactly one number from each row of a given m x n matrix such that the greatest common divisor (GCD) of all chosen numbers is 1. In other words, we need to count all valid combinations of one element per...

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LeetCode 3818 - Minimum Prefix Removal to Make Array Strictly Increasing

LeetCode Problem 3818 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem asks us to process an integer array nums and determine the minimum length of a prefix that we can remove so that the remaining array becomes strictly increasing. A prefix is any number of contiguous elements starting from the beginning of the array, including possibly zero elements (meaning we may not need to remove anything). A strictly...

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LeetCode 3724 - Minimum Operations to Transform Array

LeetCode Problem 3724 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding This problem asks us to transform an array nums1 of length n into another array nums2 of length n + 1 using the minimum number of operations. The allowed operations are increasing or decreasing any element of nums1 by 1, or appending any element of nums1 to the end of the array. The goal is to make nums1...

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LeetCode 3721 - Longest Balanced Subarray II

LeetCode Problem 3721 Difficulty: 🔴 Hard Topics: Array, Hash Table, Divide and Conquer, Segment Tree, Prefix Sum Solution Problem Understanding The problem requires us to find the length of the longest subarray in an integer array nums where the count of distinct even numbers equals the count of distinct odd numbers . A subarray is a contiguous section of the array, and “distinct” means that duplicate values are counted only...

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LeetCode 3717 - Minimum Operations to Make the Array Beautiful

LeetCode Problem 3717 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Here is the complete, detailed technical solution guide for LeetCode 3717 - Minimum Operations to Make the Array Beautiful following your exact formatting rules. Problem Understanding The problem asks us to transform an integer array nums into a beautiful array . An array is considered beautiful if every element (except the first) is divisible by its previous element. Formally,...

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LeetCode 3712 - Sum of Elements With Frequency Divisible by K

LeetCode Problem 3712 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to compute the sum of all elements in the array whose total frequency is divisible by a given integer k . To understand the requirement clearly, we need to focus on two important details: First, we must determine how many times each number appears in the array. This is the element's frequency...

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LeetCode 3811 - Number of Alternating XOR Partitions

LeetCode Problem 3811 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation Solution LeetCode 3811 - Number of Alternating XOR Partitions Problem Understanding We are given an array nums and two distinct target XOR values, target1 and target2 . A partition divides the array into contiguous, non-empty blocks. Every element must belong to exactly one block, and the blocks must cover the entire array. The partition is considered...

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LeetCode 3711 - Maximum Transactions Without Negative Balance

LeetCode Problem 3711 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Here is a complete, detailed technical solution guide for LeetCode 3711 - Maximum Transactions Without Negative Balance , following your formatting instructions precisely. Problem Understanding The problem provides an array transactions of integers representing sequential money movements in an account. Positive values correspond to receiving money, while negative values correspond to sending money. The account starts at...

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LeetCode 3710 - Maximum Partition Factor

LeetCode Problem 3710 Difficulty: 🔴 Hard Topics: Array, Binary Search, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory Solution Problem Understanding The problem asks us to split a set of n points in a 2D Cartesian plane into exactly two non-empty groups, such that the minimum Manhattan distance among all pairs of points within each group (the partition factor) is maximized. The Manhattan distance between points [xi, yi] and [xj, yj]...

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LeetCode 3709 - Design Exam Scores Tracker

LeetCode Problem 3709 Difficulty: 🟡 Medium Topics: Array, Binary Search, Design, Prefix Sum Solution Problem Understanding This problem asks us to design a system that tracks Alice's exam scores over time and efficiently computes the total score for any given time interval. The system must support two operations: recording a new exam with a timestamp and score, and querying the total score of exams between two timestamps inclusive. The input...

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LeetCode 3805 - Count Caesar Cipher Pairs

LeetCode Problem 3805 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, String, Counting Solution LeetCode 3805 - Count Caesar Cipher Pairs Problem Understanding We are given an array words containing n lowercase strings. Every string has the same length m . Two strings are considered similar if we can repeatedly apply the following operation to either string: Shift every character forward by one position in the alphabet. The alphabet wraps...

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LeetCode 3702 - Longest Subsequence With Non-Zero Bitwise XOR

LeetCode Problem 3702 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding We are given an integer array nums , and we must determine the maximum possible length of a subsequence whose bitwise XOR is not equal to zero . A subsequence is formed by deleting zero or more elements from the array while preserving the relative order of the remaining elements. Unlike subarrays, subsequences do not need to...

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LeetCode 3806 - Maximum Bitwise AND After Increment Operations

LeetCode Problem 3806 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation, Sorting Solution Problem Understanding The problem asks us to find the maximum possible bitwise AND of any subset of size m from an array nums after performing up to k increment operations . Each operation allows us to increase any element in the array by 1. The output is the largest integer that can be obtained as the bitwise...

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LeetCode 3804 - Number of Centered Subarrays

LeetCode Problem 3804 Difficulty: 🟡 Medium Topics: Array, Hash Table, Enumeration Solution Problem Understanding The problem asks us to count the number of centered subarrays in a given integer array nums . A subarray is called centered if the sum of its elements is equal to at least one element within that subarray . In simpler terms, for every contiguous sequence of numbers in nums , we need to check...

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LeetCode 3799 - Word Squares II

LeetCode Problem 3799 Difficulty: 🟡 Medium Topics: Array, String, Backtracking, Sorting, Enumeration Solution LeetCode 3799 - Word Squares II Problem Understanding We are given an array of distinct 4-letter words. Our goal is to construct every valid word square consisting of exactly four different words: top forms the top row. bottom forms the bottom row. left forms the left column. right forms the right column. Since each word has length...

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LeetCode 3801 - Minimum Cost to Merge Sorted Lists

LeetCode Problem 3801 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Bit Manipulation Solution Problem Understanding We are given between 2 and 12 sorted lists. At any moment we may choose any two existing lists and merge them. If the two lists are $a$ and $b$, the merge cost is $$\operatorname{len}(a)+\operatorname{len}(b)+ \left|\operatorname{median}(a)-\operatorname{median}(b)\right|.$$ After the merge, the two lists disappear and are replaced by their sorted union. The...

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LeetCode 3698 - Split Array With Minimum Difference

LeetCode Problem 3698 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution I can write the full detailed guide, but I need to flag one issue first: the problem statement for LeetCode 3698 - Split Array With Minimum Difference appears inconsistent with the provided Go stub and the current LeetCode catalog. Before I produce a rigorous reference-quality solution, I need to confirm the exact problem definition, because there is a high...

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LeetCode 3696 - Maximum Distance Between Unequal Words in Array I

LeetCode Problem 3696 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding The problem gives us an array of strings, words , and asks us to find the maximum distance between two indices i and j where the words at those positions are different . More formally, we want to find two indices such that: words[i] != words[j] i < j the value j - i + 1 is as...

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LeetCode 3685 - Subsequence Sum After Capping Elements

LeetCode Problem 3685 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Dynamic Programming, Sorting Solution Here is a complete, rigorous study companion-style solution guide for LeetCode 3685 - Subsequence Sum After Capping Elements , following your requested format and voice. Problem Understanding We are given an integer array nums of size n and a positive integer k . For any integer x from 1 to n , we define the capped...

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LeetCode 3795 - Minimum Subarray Length With Distinct Sum At Least K

LeetCode Problem 3795 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 3795: Minimum Subarray Length With Distinct Sum At Least K Problem Understanding This problem asks us to find the shortest contiguous subarray whose distinct-value sum is at least k . The important detail is that we do not sum all elements in the subarray. Instead, each distinct value contributes to the sum exactly once, regardless of...

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LeetCode 3755 - Find Maximum Balanced XOR Subarray Length

LeetCode Problem 3755 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Prefix Sum Solution LeetCode 3755 - Find Maximum Balanced XOR Subarray Length Problem Understanding This problem asks us to find the longest contiguous subarray that simultaneously satisfies two independent conditions: The bitwise XOR of all elements in the subarray is equal to 0 . The subarray contains an equal number of even and odd elements. We are given...

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LeetCode 3742 - Maximum Path Score in a Grid

LeetCode Problem 3742 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem presents a grid of size m x n where each cell contains a value of 0, 1, or 2. Each cell contributes both a score and a cost: a cell with value 0 adds 0 to both score and cost, a cell with value 1 adds 1 to score and 1 to cost, and...

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LeetCode 3729 - Count Distinct Subarrays Divisible by K in Sorted Array

LeetCode Problem 3729 Difficulty: 🔴 Hard Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to find the number of distinct subarrays in a sorted array nums such that the sum of elements in the subarray is divisible by a given integer k . A subarray is a contiguous segment of the original array, and two subarrays are considered distinct if their sequences of values differ,...

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LeetCode 3718 - Smallest Missing Multiple of K

LeetCode Problem 3718 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem asks us to find the smallest positive multiple of k that is not present in a given integer array nums . In other words, if we consider the infinite sequence of numbers k, 2k, 3k, 4k… , we need to identify the first number in this sequence that does not appear in nums . The...

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LeetCode 3708 - Longest Fibonacci Subarray

LeetCode Problem 3708 Difficulty: 🟡 Medium Topics: Array Solution LeetCode 3708 - Longest Fibonacci Subarray Problem Understanding The problem gives us an array nums consisting of positive integers and asks us to find the length of the longest contiguous subarray that satisfies the Fibonacci property. A subarray is a contiguous segment of the original array. For a sequence to be considered Fibonacci, every element from the third position onward must...

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LeetCode 3691 - Maximum Total Subarray Value II

LeetCode Problem 3691 Difficulty: 🔴 Hard Topics: Array, Greedy, Segment Tree, Heap (Priority Queue) Solution Problem Understanding The problem is asking us to select exactly k distinct subarrays from a given integer array nums such that the sum of their "values" is maximized. Each subarray's value is calculated as the difference between its maximum and minimum elements. Subarrays may overlap, but the exact same subarray (defined by the same start...

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LeetCode 3690 - Split and Merge Array Transformation

LeetCode Problem 3690 Difficulty: 🟡 Medium Topics: Array, Hash Table, Breadth-First Search Solution LeetCode 3690 - Split and Merge Array Transformation Problem Understanding The problem gives us two arrays, nums1 and nums2 , of equal length n . We are allowed to repeatedly perform a special operation on nums1 . In a single operation, we choose any contiguous subarray, remove it from its current location, and then insert that entire...

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LeetCode 3681 - Maximum XOR of Subsequences

LeetCode Problem 3681 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation Solution LeetCode 3681 - Maximum XOR of Subsequences Problem Understanding The problem gives us an array nums of non-negative integers. We must choose two subsequences: The first subsequence has XOR value X . The second subsequence has XOR value Y . The two subsequences: May be empty. Must preserve the original order of elements, as all subsequences do....

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LeetCode 3679 - Minimum Discards to Balance Inventory

LeetCode Problem 3679 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window, Simulation, Counting Solution LeetCode 3679 - Minimum Discards to Balance Inventory Problem Understanding This problem models a stream of arriving items. On each day, exactly one item arrives, and each item has a type represented by an integer. We are given two parameters: w , the size of the sliding window. m , the maximum number of times...

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LeetCode 3661 - Maximum Walls Destroyed by Robots

LeetCode Problem 3661 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Sorting Solution LeetCode 3661 - Maximum Walls Destroyed by Robots Problem Understanding This problem takes place on a one dimensional number line. We are given positions of robots and positions of walls. Every robot owns exactly one bullet, and that bullet can be fired either to the left or to the right. A robot located at position robots[i]...

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LeetCode 3654 - Minimum Sum After Divisible Sum Deletions

LeetCode Problem 3654 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Prefix Sum Solution LeetCode 3654 - Minimum Sum After Divisible Sum Deletions Problem Understanding This problem gives us an array nums containing positive integers and an integer k . We may repeatedly remove any contiguous subarray whose sum is divisible by k . After each removal, the remaining elements close the gap, meaning the array becomes shorter and...

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LeetCode 3635 - Earliest Finish Time for Land and Water Rides II

LeetCode Problem 3635 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Great! We will cover LeetCode 3627 - Maximum Median Sum of Subsequences of Size 3 in a full, comprehensive technical guide following your formatting requirements. Problem Understanding The problem gives us an integer array nums with a length divisible by 3. We are asked to remove the array in steps by selecting any three elements...

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LeetCode 3595 - Once Twice

LeetCode Problem 3595 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem provides an integer array nums where every element appears exactly three times , except for one element that appears once and one element that appears twice . We are asked to identify these two unique elements and return them as a list, with the element appearing once first and the element appearing twice second. The...

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LeetCode 3593 - Minimum Increments to Equalize Leaf Paths

LeetCode Problem 3593 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution LeetCode 3593 - Minimum Increments to Equalize Leaf Paths Problem Understanding We are given a rooted tree with root node 0 . Every node has a cost, and the score of a root-to-leaf path is the sum of the costs of all nodes along that path. We are allowed to increase the cost of any nodes...

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LeetCode 3590 - Kth Smallest Path XOR Sum

LeetCode Problem 3590 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Ordered Set Solution Problem Understanding The problem asks us to work with an undirected tree rooted at node 0, where each node has a value vals[i] and a parent par[i] . We are asked to calculate the path XOR sum for each node, which is defined as the XOR of all vals[i] along the path from the root to...

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LeetCode 3572 - Maximize Y‑Sum by Picking a Triplet of Distinct X‑Values

LeetCode Problem 3572 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue) Solution LeetCode 3572 - Maximize Y-Sum by Picking a Triplet of Distinct X-Values Problem Understanding The problem gives us two arrays, x and y , both of length n . Each position i represents a pair (x[i], y[i]) . We need to select exactly three distinct indices i , j , and k such that...

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LeetCode 3566 - Partition Array into Two Equal Product Subsets

LeetCode Problem 3566 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Recursion, Enumeration Solution Here’s a detailed technical solution guide for LeetCode 3566 following your formatting rules: Problem Understanding The problem asks us to determine whether a given array of distinct positive integers can be split into two non-empty, disjoint subsets , such that the product of the elements in each subset equals a given target value . Each element of...

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LeetCode 3534 - Path Existence Queries in a Graph II

LeetCode Problem 3534 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Greedy, Bit Manipulation, Graph Theory, Sorting Solution Problem Understanding This problem asks us to compute the shortest path between nodes in an implicit undirected graph defined by a nums array and a maxDiff . Each node i corresponds to nums[i] . There is an edge between nodes i and j if the absolute difference of their...

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LeetCode 3506 - Find Time Required to Eliminate Bacterial Strains

LeetCode Problem 3506 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Heap (Priority Queue) Solution Problem Understanding This problem asks us to find the minimum time required to eliminate all bacterial strains given a single initial white blood cell (WBC) and the ability of WBCs to split into two after some splitTime . Each bacterial strain has a specific time requirement timeReq[i] to be eliminated by a single WBC. The WBCs...

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LeetCode 3505 - Minimum Operations to Make Elements Within K Subarrays Equal

LeetCode Problem 3505 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Sliding Window, Heap (Priority Queue) Solution Problem Understanding You are given an integer array nums , and you want to create at least k non-overlapping subarrays. Every chosen subarray must have length exactly x , and after performing some modifications, every element inside each chosen subarray must become equal. The only allowed operation is increasing or decreasing...

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LeetCode 3468 - Find the Number of Copy Arrays

LeetCode Problem 3468 Difficulty: 🟡 Medium Topics: Array, Math Solution LeetCode 3468 - Find the Number of Copy Arrays Problem Understanding We are given an array original and a range constraint for every position in the form of bounds[i] = [ui, vi] . We need to count how many arrays copy satisfy two conditions. The first condition states that the difference between consecutive elements in copy must be exactly the...

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LeetCode 3464 - Maximize the Distance Between Points on a Square

LeetCode Problem 3464 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Geometry, Sorting Solution LeetCode 3464 - Maximize the Distance Between Points on a Square Problem Understanding We are given a square of side length side . Every point in the input lies somewhere on the boundary of this square. We must choose exactly k points from the given set. For any two selected points, we can compute their Manhattan...

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LeetCode 3453 - Separate Squares I

LeetCode Problem 3453 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution LeetCode 3453 - Separate Squares I Problem Understanding We are given a collection of axis-aligned squares. Each square is represented by three integers: xi : x-coordinate of the bottom-left corner yi : y-coordinate of the bottom-left corner li : side length The square therefore occupies the region: $$[x_i, x_i + l_i] \times [y_i, y_i + l_i]$$ We must find...

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LeetCode 3414 - Maximum Score of Non-overlapping Intervals

LeetCode Problem 3414 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Sorting Solution Problem Understanding This problem combines weighted interval scheduling with an additional constraint: we may select at most 4 intervals, and if multiple selections achieve the same maximum total weight, we must return the lexicographically smallest list of original indices. Each interval is represented as: [left, right, weight] where: left is the starting position right is the...

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LeetCode 3402 - Minimum Operations to Make Columns Strictly Increasing

LeetCode Problem 3402 Difficulty: 🟢 Easy Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives us a matrix grid of size m x n containing non-negative integers. Each column must become strictly increasing , meaning for each column j , the condition grid[i][j] < grid[i+1][j] must hold for all 0 <= i < m-1 . We are allowed to perform operations that increment any element by 1 , and...

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LeetCode 3770 - Largest Prime from Consecutive Prime Sum

LeetCode Problem 3770 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 3770 - Largest Prime from Consecutive Prime Sum Problem Understanding The problem gives us an integer n and asks us to find the largest prime number that satisfies two conditions: It is less than or equal to n . It can be written as the sum of one or more consecutive prime numbers starting from 2 ....

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LeetCode 3768 - Minimum Inversion Count in Subarrays of Fixed Length

LeetCode Problem 3768 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Sliding Window Solution LeetCode 3768 - Minimum Inversion Count in Subarrays of Fixed Length Problem Understanding We are given an array nums of length n and an integer k . For every contiguous subarray of length k , we must compute its inversion count, then return the smallest inversion count among all such windows. An inversion is a pair of...

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LeetCode 3762 - Minimum Operations to Equalize Subarrays

LeetCode Problem 3762 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Segment Tree Solution Problem Understanding We are given an array nums and a fixed integer k . A single operation allows us to choose any element and either increase it by exactly k or decrease it by exactly k . We may perform as many operations as needed. For each query [l, r] , we only consider the subarray...

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LeetCode 3748 - Count Stable Subarrays

LeetCode Problem 3748 Difficulty: 🔴 Hard Topics: Array, Binary Search, Prefix Sum Solution Problem Understanding The problem asks us to count "stable" subarrays within a given array nums . A subarray is stable if it contains no inversions , which means that for any two indices i < j in the subarray, nums[i] <= nums[j] . Essentially, a stable subarray is non-decreasing . We are given multiple queries [li, ri]...

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LeetCode 3745 - Maximize Expression of Three Elements

LeetCode Problem 3745 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Enumeration Solution LeetCode 3745 - Maximize Expression of Three Elements Problem Understanding The problem gives us an integer array nums and asks us to choose three elements a , b , and c from distinct indices such that the expression: $$a + b - c$$ is as large as possible. The important detail is that the three elements must come...

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LeetCode 3743 - Maximize Cyclic Partition Score

LeetCode Problem 3743 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding We are given a cyclic array nums , which means the array is considered to wrap around from the last element back to the first element. We want to partition the entire cycle into at most k contiguous subarrays. Since the array is cyclic, one of the subarrays is allowed to cross the boundary between the last...

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LeetCode 3727 - Maximum Alternating Sum of Squares

LeetCode Problem 3727 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution LeetCode 3727 - Maximum Alternating Sum of Squares Problem Understanding We are given an integer array nums , and we are allowed to rearrange its elements in any order before computing a score. The score of a rearranged array arr is defined as: $$arr[0]^2 - arr[1]^2 + arr[2]^2 - arr[3]^2 + \cdots$$ The sign alternates between positive and negative...

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LeetCode 3715 - Sum of Perfect Square Ancestors

LeetCode Problem 3715 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Tree, Depth-First Search, Counting, Number Theory Solution Problem Understanding This problem asks us to compute a sum across all non-root nodes in a tree based on ancestor relationships and the property of perfect squares. We are given a rooted tree of n nodes, represented as an edge list. Each node has a positive integer value from the nums array....

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LeetCode 3706 - Maximum Distance Between Unequal Words in Array II

LeetCode Problem 3706 Difficulty: 🟡 Medium Topics: Array, String Solution LeetCode 3706 - Maximum Distance Between Unequal Words in Array II Problem Understanding We are given an array of strings called words . Our goal is to find two different indices i and j such that the strings at those positions are different, meaning words[i] != words[j] . For every valid pair, the distance is defined as: $$j - i...

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LeetCode 3697 - Compute Decimal Representation

LeetCode Problem 3697 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding This problem asks us to decompose a positive integer n into the fewest possible base-10 components , where a base-10 component is defined as a single digit (1-9) multiplied by a power of 10. Essentially, we are breaking n down into its decimal place contributions . For example, for n = 537 , the hundreds place contributes 500,...

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LeetCode 3695 - Maximize Alternating Sum Using Swaps

LeetCode Problem 3695 Difficulty: 🔴 Hard Topics: Array, Greedy, Union-Find, Sorting Solution LeetCode 3695 - Maximize Alternating Sum Using Swaps Problem Understanding We are given an array nums and a list of allowed swap operations. The alternating sum of an array is defined as: $$nums[0] - nums[1] + nums[2] - nums[3] + \cdots$$ Elements at even indices contribute positively, while elements at odd indices contribute negatively. The important detail is...

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LeetCode 3693 - Climbing Stairs II

LeetCode Problem 3693 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem is an extension of the classic "climbing stairs" dynamic programming problem but with more complex jump costs. You are given a staircase with n + 1 steps, numbered from 0 to n . Each intermediate step i (1-indexed) has an associated cost costs[i] . You start at step 0 with zero cost. From any step...

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LeetCode 3689 - Maximum Total Subarray Value I

LeetCode Problem 3689 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem asks us to select exactly k non-empty subarrays from a given integer array nums , where subarrays may overlap and can even be identical. For each chosen subarray nums[l..r] , we compute its value as the difference between its maximum and minimum element, specifically max(nums[l..r]) - min(nums[l..r]) . The goal is to maximize the total sum...

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LeetCode 3686 - Number of Stable Subsequences

LeetCode Problem 3686 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to count how many subsequences of a given integer array are stable , where stability is defined by a constraint on parity patterns inside the subsequence itself. A subsequence is formed by deleting zero or more elements without changing the relative order of the remaining elements. A subsequence is considered unstable if, when...

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LeetCode 3688 - Bitwise OR of Even Numbers in an Array

LeetCode Problem 3688 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Simulation Solution Problem Understanding This problem asks us to compute the bitwise OR of all even numbers in a given integer array nums . A number is considered even if it is divisible by 2, meaning its least significant bit is 0. The task is to iterate through the array, select only the even numbers, and combine them using the...

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LeetCode 3683 - Earliest Time to Finish One Task

LeetCode Problem 3683 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3683 - Earliest Time to Finish One Task Problem Understanding The problem gives us a list of tasks, where each task is represented by two integers: si , the time when the task starts. ti , the amount of time required to complete the task. A task finishes at time: $$\text{finishTime} = s_i + t_i$$ Our goal is to determine...

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LeetCode 3684 - Maximize Sum of At Most K Distinct Elements

LeetCode Problem 3684 Difficulty: 🟢 Easy Topics: Array, Hash Table, Greedy, Sorting Solution Problem Understanding This problem requires selecting at most k distinct elements from a given array of positive integers nums such that their sum is maximized. The result must be returned as a list sorted in strictly descending order . The input nums represents a collection of numbers from which we can pick a subset. Each number can...

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LeetCode 3682 - Minimum Index Sum of Common Elements

LeetCode Problem 3682 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding This problem is asking us to identify the smallest sum of indices from two equal-length arrays, nums1 and nums2 , such that the elements at those indices are equal. Formally, we want a pair (i, j) where nums1[i] == nums2[j] , and we want the minimum value of i + j . If no such pair exists,...

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LeetCode 3680 - Generate Schedule

LeetCode Problem 3680 Difficulty: 🟡 Medium Topics: Array, Math, Greedy Solution Problem Understanding The problem is asking us to generate a round-robin style schedule for n teams, where each team plays every other team exactly twice, once at home and once away. Each day in the schedule can host exactly one match, and a team is not allowed to play on consecutive days. The input is simply an integer n...

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LeetCode 3676 - Count Bowl Subarrays

LeetCode Problem 3676 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution Problem Understanding The problem asks us to count how many subarrays in an array of distinct integers satisfy a specific “bowl” condition. A subarray nums[l...r] is considered a bowl if it has length at least 3 and the smaller of its two endpoints is strictly greater than the maximum value of all elements strictly inside the subarray. In...

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LeetCode 3674 - Minimum Operations to Equalize Array

LeetCode Problem 3674 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Brainteaser Solution Let's go step by step and produce a fully detailed, reference-style solution guide for LeetCode 3674 following your requested formatting. Problem Understanding The problem asks us to make all elements of an integer array nums equal using the minimum number of operations. Each operation consists of selecting a contiguous subarray and replacing every element in that subarray with...

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LeetCode 3667 - Sort Array By Absolute Value

LeetCode Problem 3667 Difficulty: 🟢 Easy Topics: Array, Math, Two Pointers, Sorting Solution Problem Understanding The problem asks us to reorder an integer array such that the elements are sorted in non-decreasing order of their absolute values . This means we are not sorting based on the actual numeric value, but rather based on how far each number is from zero on the number line, regardless of sign. In simpler...

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LeetCode 3668 - Restore Finishing Order

LeetCode Problem 3668 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3668 - Restore Finishing Order Problem Understanding This problem gives us two arrays: order , which represents the finishing order of all participants in a race. friends , which contains the IDs of our friends. The array order is a permutation of the integers from 1 to n , meaning every participant appears exactly once. The position of...

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LeetCode 3665 - Twisted Mirror Path Count

LeetCode Problem 3665 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to count all unique paths from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) of a binary grid where certain cells contain mirrors. The robot can move only right or down , but mirrors change its trajectory in a very specific way: moving right into...

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LeetCode 3664 - Two-Letter Card Game

LeetCode Problem 3664 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting, Enumeration Solution Problem Understanding Each card consists of exactly two lowercase letters. A card is only relevant if it contains the given letter x somewhere in its two positions. During the game, we repeatedly select two cards that satisfy two conditions: Both cards contain the letter x . The two strings differ in exactly one position. After selecting...

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LeetCode 3663 - Find The Least Frequent Digit

LeetCode Problem 3663 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Counting Solution Problem Understanding The problem asks us to find the least frequent digit in the decimal representation of a given integer n . In other words, we need to count how many times each digit from 0 to 9 appears in the number, and then return the smallest digit that occurs the fewest times. The input is a...

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LeetCode 3651 - Minimum Cost Path with Teleportations

LeetCode Problem 3651 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem asks us to find the minimum cost to travel from the top-left corner (0, 0) of a 2D grid to the bottom-right corner (m - 1, n - 1) . Each cell contains a non-negative integer representing its cost. There are two ways to move: Normal move : move either right or down, paying...

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LeetCode 3655 - XOR After Range Multiplication Queries II

LeetCode Problem 3655 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer Solution Problem Understanding We are given an array nums and a list of queries. Each query has the form: [li, ri, ki, vi] For a query, we start at index li and repeatedly jump forward by ki until we pass ri . Every visited position is multiplied by vi , and the result is taken modulo 10^9 + 7...

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LeetCode 3653 - XOR After Range Multiplication Queries I

LeetCode Problem 3653 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Simulation Solution LeetCode 3653 - XOR After Range Multiplication Queries I Problem Understanding We are given an integer array nums and a list of queries. Each query has the form: [li, ri, ki, vi] For a query, we start at index li and repeatedly move forward by ki positions until we exceed ri . Every visited index is updated...

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LeetCode 3652 - Best Time to Buy and Sell Stock using Strategy

LeetCode Problem 3652 Difficulty: 🟡 Medium Topics: Array, Sliding Window, Prefix Sum Solution Problem Understanding This problem asks us to calculate the maximum possible profit from a stock trading strategy with the option to modify it once in a very specific way. You are given two arrays: prices , which contains the stock price on each day, and strategy , which tells you what action to take each day: -1...

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LeetCode 3647 - Maximum Weight in Two Bags

LeetCode Problem 3647 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem asks us to distribute a set of items, each with a given weight, into two separate bags with fixed capacity limits, in order to maximize the total weight placed across both bags. Each item in the input array weights can be used at most once, and for each item we must decide one of three...

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LeetCode 3643 - Flip Square Submatrix Vertically

LeetCode Problem 3643 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Matrix Solution LeetCode 3643 - Flip Square Submatrix Vertically Problem Understanding This problem gives us an m x n matrix called grid and three integers: x , y , and k . The values x and y specify the top-left corner of a square submatrix, while k specifies the side length of that square. Therefore, the submatrix occupies: Problem Understanding...

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LeetCode 3640 - Trionic Array II

LeetCode Problem 3640 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding We are given an integer array nums , and we must find the maximum possible sum of a contiguous subarray that follows a very specific shape: It first increases strictly. Then decreases strictly. Then increases strictly again. More formally, for a subarray nums[l...r] , there must exist indices: l < p < q < r such that:...

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LeetCode 3641 - Longest Semi-Repeating Subarray

LeetCode Problem 3641 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 3641 - Longest Semi-Repeating Subarray Problem Understanding We are given an integer array nums and an integer k . A subarray is considered semi-repeating if the number of distinct values that appear more than once inside that subarray is at most k . To understand this carefully, consider a frequency map for a subarray: If a...

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LeetCode 3636 - Threshold Majority Queries

LeetCode Problem 3636 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Divide and Conquer, Counting, Prefix Sum Solution Problem Understanding The problem asks us to process multiple queries on a given array nums where each query specifies a subarray defined by [li, ri] and a threshold . For each query, we need to find an element in the subarray that appears at least threshold times. If multiple elements meet...

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LeetCode 3638 - Maximum Balanced Shipments

LeetCode Problem 3638 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding We are given an array weight representing parcels arranged in a line. We must partition some prefix-suffix segments of this array into a collection of non-overlapping contiguous subarrays called shipments. Each parcel can belong to at most one shipment, and it is also allowed to leave some parcels unused. A shipment is considered...

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LeetCode 3632 - Subarrays with XOR at Least K

LeetCode Problem 3632 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Prefix Sum Solution Problem Understanding This problem asks us to count the number of contiguous subarrays of a given array nums such that the bitwise XOR of all elements in the subarray is greater than or equal to a given integer k . The input array nums consists of positive integers, and k is a non-negative integer. A contiguous...

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LeetCode 3630 - Partition Array for Maximum XOR and AND

LeetCode Problem 3630 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to partition an integer array nums into three subsequences A , B , and C such that every element belongs to exactly one subsequence. The goal is to maximize the sum XOR(A) + AND(B) + XOR(C) , where XOR and AND represent the bitwise XOR and AND of the elements...

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LeetCode 3625 - Count Number of Trapezoids II

LeetCode Problem 3625 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Geometry Solution Problem Understanding The problem asks us to count the number of unique trapezoids that can be formed from a set of points on a 2D Cartesian plane. Each point is given as a pair of integers representing its x and y coordinates. A trapezoid is defined as a convex quadrilateral with at least one pair of parallel...

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LeetCode 3620 - Network Recovery Pathways

LeetCode Problem 3620 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Graph Theory, Topological Sort, Heap (Priority Queue), Shortest Path Solution LeetCode 3620 - Network Recovery Pathways Problem Understanding We are given a directed acyclic graph (DAG) with n nodes numbered from 0 to n - 1 . Each directed edge is represented as: u -> v with cost c and stored in: edges[i] = [u, v, c] We...

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LeetCode 3619 - Count Islands With Total Value Divisible by K

LeetCode Problem 3619 Difficulty: 🟡 Medium Topics: Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix Solution Problem Understanding The problem is asking us to count islands in a 2D grid where the sum of the values in each island is divisible by a given integer k . An island is defined as a group of positive integers that are 4-directionally connected, meaning we can move horizontally or vertically between adjacent positive...

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LeetCode 3618 - Split Array by Prime Indices

LeetCode Problem 3618 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 3618 - Split Array by Prime Indices Problem Understanding The problem gives us an integer array nums and asks us to divide its elements into two groups based on their indices. Array A contains all elements whose indices are prime numbers. Array B contains all remaining elements, meaning indices that are not prime. Remember that array indices...

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LeetCode 3605 - Minimum Stability Factor of Array

LeetCode Problem 3605 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Greedy, Segment Tree, Number Theory Solution LeetCode 3605 - Minimum Stability Factor of Array Problem Understanding We are given an array nums and an integer maxC . A subarray is called stable if the greatest common divisor (HCF/GCD) of all elements in that subarray is at least 2 . The stability factor of the entire array is defined as...

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LeetCode 3606 - Coupon Code Validator

LeetCode Problem 3606 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Sorting Solution Problem Understanding The problem is asking us to validate a set of coupons based on three criteria: the coupon code must be a non-empty string containing only alphanumeric characters or underscores, the business line must belong to a set of four predefined categories, and the coupon must be active. We are given three arrays of equal length,...

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LeetCode 3607 - Power Grid Maintenance

LeetCode Problem 3607 Difficulty: 🟡 Medium Topics: Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem gives an undirected graph of c power stations labeled from 1 to c , connected by bidirectional cables. These connections define connected components, which are referred to as power grids. Importantly, these grids are static, meaning connectivity does not change even if stations...

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LeetCode 3599 - Partition Array to Minimize XOR

LeetCode Problem 3599 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Prefix Sum Solution Problem Understanding This problem asks us to partition an array of integers, nums , into exactly k non-empty contiguous subarrays, and then compute the bitwise XOR of each subarray. The goal is to minimize the maximum XOR among these subarrays. Essentially, we are trying to distribute the elements into k groups such that the "largest...

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LeetCode 3594 - Minimum Time to Transport All Individuals

LeetCode Problem 3594 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Graph Theory, Heap (Priority Queue), Shortest Path, Bitmask Solution Problem Understanding This problem is a shortest-path optimization over a highly constrained state space where you are repeatedly moving groups of people across a river using a single boat. The twist is that the travel time is not fixed: it depends both on the slowest person in the group and on...

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LeetCode 3592 - Inverse Coin Change

LeetCode Problem 3592 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem gives us a 1-indexed array numWays , where numWays[i] indicates the number of ways to form a total amount i using an infinite supply of some unknown coin denominations . The goal is to recover the original set of coin denominations. The array effectively represents the output of a classical coin change problem, but in...

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LeetCode 3591 - Check if Any Element Has Prime Frequency

LeetCode Problem 3591 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Counting, Number Theory Solution Problem Understanding This problem asks us to determine whether any number in an array appears a prime number of times. In other words, for each unique number in the input array nums , we calculate its frequency-the number of occurrences-and check if that frequency is a prime number. If at least one element has a...

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LeetCode 3589 - Count Prime-Gap Balanced Subarrays

LeetCode Problem 3589 Difficulty: 🟡 Medium Topics: Array, Math, Queue, Sliding Window, Number Theory, Monotonic Queue Solution Count Prime-Gap Balanced Subarrays Problem Understanding We are given an integer array nums and an integer k . We must count how many contiguous subarrays satisfy two conditions: The subarray contains at least two prime numbers. Among all prime numbers inside that subarray, the difference between the largest prime and the smallest prime...

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LeetCode 3585 - Find Weighted Median Node in Tree

LeetCode Problem 3585 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted tree with n nodes. A tree is an undirected connected graph with exactly n - 1 edges, which guarantees that there is exactly one simple path between any two nodes. Each edge has a positive weight. For every query [u, v] , we look at...

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LeetCode 3588 - Find Maximum Area of a Triangle

LeetCode Problem 3588 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy, Geometry, Enumeration Solution LeetCode 3588 - Find Maximum Area of a Triangle Problem Understanding We are given n distinct points on a 2D Cartesian plane. Each point is represented as [x, y] . We must choose any three points that form a non-degenerate triangle, meaning the area must be strictly greater than zero. Among all valid triangles, we...

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LeetCode 3578 - Count Partitions With Max-Min Difference at Most K

LeetCode Problem 3578 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Queue, Sliding Window, Prefix Sum, Monotonic Queue Solution LeetCode 3578 - Count Partitions With Max-Min Difference at Most K Problem Understanding We are given an array nums and an integer k . We want to split the array into one or more contiguous, non-empty segments. Every element must belong to exactly one segment, and the segments must preserve the original...

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LeetCode 3577 - Count the Number of Computer Unlocking Permutations

LeetCode Problem 3577 Difficulty: 🟡 Medium Topics: Array, Math, Brainteaser, Combinatorics Solution Problem Understanding The problem presents a set of n computers, each with a unique password complexity represented in an array complexity of length n . The computers are labeled 0 to n - 1 , and only computer 0 is initially unlocked. To unlock another computer i , you must already have unlocked at least one computer j...

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LeetCode 3573 - Best Time to Buy and Sell Stock V

LeetCode Problem 3573 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 3573 - Best Time to Buy and Sell Stock V Problem Understanding This problem extends the classic stock trading dynamic programming family by allowing two different kinds of transactions. A normal transaction consists of buying first and selling later. If the stock price rises, the profit is: $$\text{sell price} - \text{buy price}$$ A short selling transaction reverses the...

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LeetCode 3574 - Maximize Subarray GCD Score

LeetCode Problem 3574 Difficulty: 🔴 Hard Topics: Array, Math, Enumeration, Number Theory Solution Problem Understanding The problem asks us to choose a contiguous subarray from an array of positive integers after performing at most k doubling operations, where each element can be doubled at most once. After applying these optional doublings, we compute the score of a subarray as the product of its length and the greatest common divisor (GCD)...

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LeetCode 3567 - Minimum Absolute Difference in Sliding Submatrix

LeetCode Problem 3567 Difficulty: 🟡 Medium Topics: Array, Sorting, Matrix Solution Problem Understanding The problem requires computing a specific statistic for every contiguous k x k submatrix of a given m x n integer matrix grid . For each submatrix, we must find the minimum absolute difference between any two distinct elements. The final result is a 2D array ans of size (m - k + 1) x (n -...

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LeetCode 3565 - Sequential Grid Path Cover

LeetCode Problem 3565 Difficulty: 🟡 Medium Topics: Array, Recursion, Matrix Solution Problem Understanding The problem asks us to find a path that visits every cell of a given m x n grid exactly once while visiting certain numbered cells in a specified order. Specifically, the grid contains integers from 1 to k in exactly one cell each, and the rest of the cells are zeros. The path can start at...

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LeetCode 3559 - Number of Ways to Assign Edge Weights II

LeetCode Problem 3559 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given an undirected tree with n nodes, rooted at node 1 . Every edge will eventually receive a weight of either 1 or 2 . For each query [u, v] , we only care about the unique path connecting u and v . All edges outside that path are...

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LeetCode 3549 - Multiply Two Polynomials

LeetCode Problem 3549 Difficulty: 🔴 Hard Topics: Array, Math Solution Problem Understanding The input arrays represent polynomials in coefficient form. If: poly1 = [a0, a1, a2, ...] then it represents: A(x) = a0 + a1x + a2x² + ... Similarly: poly2 = [b0, b1, b2, ...] represents: B(x) = b0 + b1x + b2x² + ... The task is to compute the product polynomial: R(x) = A(x) × B(x) and...

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LeetCode 3553 - Minimum Weighted Subgraph With the Required Paths II

LeetCode Problem 3553 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted, undirected tree with n nodes. Because the graph is a tree, there is exactly one simple path between any two nodes. For each query [src1, src2, dest] , we must find the minimum total weight of a connected subtree such that both src1 and src2 can reach...

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LeetCode 3552 - Grid Teleportation Traversal

LeetCode Problem 3552 Difficulty: 🟡 Medium Topics: Array, Hash Table, Breadth-First Search, Matrix Solution Problem Understanding This problem presents a 2D grid traversal scenario with obstacles and teleportation portals. You are given a matrix of characters representing cells. Empty cells '.' are freely passable, '#' represents obstacles that block movement, and uppercase letters 'A' - 'Z' are teleportation portals. The task is to move from the top-left (0, 0) to...

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LeetCode 3546 - Equal Sum Grid Partition I

LeetCode Problem 3546 Difficulty: 🟡 Medium Topics: Array, Matrix, Enumeration, Prefix Sum Solution LeetCode 3546 - Equal Sum Grid Partition I Problem Understanding This problem asks us to determine whether a rectangular grid of positive integers can be split into two parts with exactly the same sum using a single straight cut. The cut can be made in only one of two ways: A horizontal cut between two adjacent rows....

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LeetCode 3544 - Subtree Inversion Sum

LeetCode Problem 3544 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search Solution Problem Understanding This problem asks us to select a subset of nodes in a rooted tree such that each selected node triggers a subtree inversion, and inversions interact through ancestor-descendant relationships with a distance constraint. Each inversion multiplies all values in the corresponding subtree by −1, and multiple inversions stack multiplicatively, meaning each node’s final sign...

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LeetCode 3542 - Minimum Operations to Convert All Elements to Zero

LeetCode Problem 3542 Difficulty: 🟡 Medium Topics: Array, Hash Table, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem requires us to reduce all elements of a given non-negative integer array nums to zero using the fewest number of operations. Each operation allows selecting a contiguous subarray and setting all occurrences of the minimum non-negative integer in that subarray to zero. In essence, we can remove the "smallest" numbers in...

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LeetCode 3540 - Minimum Time to Visit All Houses

LeetCode Problem 3540 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution LeetCode 3540 - Minimum Time to Visit All Houses Problem Understanding This problem describes a set of n houses arranged in a circle. Between adjacent houses, there are two directed road systems: forward[i] is the distance from house i to (i + 1) % n . backward[i] is the distance from house i to (i - 1 + n)...

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LeetCode 3538 - Merge Operations for Minimum Travel Time

LeetCode Problem 3538 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding This problem presents a road of length l kilometers, segmented by n signs at strictly increasing positions, where the first sign is at the start of the road ( position[0] = 0 ) and the last sign is at the end of the road ( position[n-1] = l ). Each segment between consecutive signs has...

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LeetCode 3535 - Unit Conversion II

LeetCode Problem 3535 Difficulty: 🟡 Medium Topics: Array, Math, Depth-First Search, Breadth-First Search, Graph Theory Solution Problem Understanding The input describes a collection of unit conversion relationships. Each conversion is given as: source -> target with factor f meaning: 1 unit of source = f units of target The important observation is that there are exactly n - 1 conversion edges among n units, and the statement guarantees that unit...

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LeetCode 3533 - Concatenated Divisibility

LeetCode Problem 3533 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution LeetCode 3533 - Concatenated Divisibility Problem Understanding We are given an array nums containing up to 13 positive integers and an integer k . We may reorder the numbers in any permutation. After choosing an ordering, we concatenate the decimal representations of the numbers to form a single large integer. The task is to find a...

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LeetCode 3529 - Count Cells in Overlapping Horizontal and Vertical Substrings

LeetCode Problem 3529 Difficulty: 🟡 Medium Topics: Array, String, Rolling Hash, String Matching, Matrix, Hash Function Solution Problem Understanding We are given a character matrix and a pattern string. The key observation is that the problem defines two unusual traversal orders: A horizontal traversal reads the matrix row by row, from left to right. When a row ends, reading continues at the beginning of the next row. A vertical traversal...

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LeetCode 3532 - Path Existence Queries in a Graph I

LeetCode Problem 3532 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Union-Find, Graph Theory Solution Path Existence Queries in a Graph I Problem Understanding This problem defines an undirected graph implicitly through a sorted array nums . Each index in nums represents a graph node. Two nodes i and j are connected by an edge whenever: $$|nums[i] - nums[j]| \le maxDiff$$ We are then given many connectivity queries. For...

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LeetCode 3530 - Maximum Profit from Valid Topological Order in DAG

LeetCode Problem 3530 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Graph Theory, Topological Sort, Bitmask Solution Problem Understanding The problem requires computing the maximum possible profit achievable by processing nodes of a Directed Acyclic Graph (DAG) in a valid topological order . Each node has a score, and the profit contribution of a node is its score multiplied by its position in the processing order (1-based). The goal...

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LeetCode 3527 - Find the Most Common Response

LeetCode Problem 3527 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting Solution LeetCode 3527 - Find the Most Common Response Problem Understanding This problem gives us a two dimensional array of strings called responses . Each responses[i] represents all survey responses collected on the i th day. A response is simply a string such as "good" , "ok" , or "bad" . The important detail is that duplicate responses...

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LeetCode 3525 - Find X Value of Array II

LeetCode Problem 3525 Difficulty: 🔴 Hard Topics: Array, Math, Segment Tree Solution Problem Understanding For each query, two things happen in order. First, we permanently update one element of nums : nums[index] = value This modification remains in effect for all future queries. Second, we conceptually remove the prefix nums[0..start-1] . After this removal, we are left with the suffix: nums[start..n-1] Now we must count how many ways we can...

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LeetCode 3524 - Find X Value of Array I

LeetCode Problem 3524 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming Solution LeetCode 3524 - Find X Value of Array I Problem Understanding The operation described in the problem may initially look unusual, but it is actually equivalent to choosing a non-empty contiguous subarray. When we remove a prefix and a suffix that do not overlap, the elements left behind form a contiguous segment of the original array. Conversely, every...

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LeetCode 3523 - Make Array Non-decreasing

LeetCode Problem 3523 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to transform an integer array nums into a non-decreasing array by performing zero or more operations, where an operation consists of selecting a contiguous subarray and replacing it with its maximum value . The goal is to maximize the size of the resulting array after all operations. In other words, we...

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LeetCode 3515 - Shortest Path in a Weighted Tree

LeetCode Problem 3515 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Binary Indexed Tree, Segment Tree Solution LeetCode 3515. Shortest Path in a Weighted Tree Problem Understanding We are given a weighted tree with n nodes, rooted at node 1 . A tree has exactly one simple path between any pair of nodes. Since the tree is rooted at node 1 , every node has a unique path from the...

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LeetCode 3514 - Number of Unique XOR Triplets II

LeetCode Problem 3514 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation, Enumeration Solution LeetCode 3514 - Number of Unique XOR Triplets II Problem Understanding We are given an integer array nums , and we must consider every triplet of indices (i, j, k) such that i <= j <= k . For each valid triplet, we compute: $$nums[i] \oplus nums[j] \oplus nums[k]$$ where ⊕ denotes the bitwise XOR operation. The...

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LeetCode 3511 - Make a Positive Array

LeetCode Problem 3511 Difficulty: 🟡 Medium Topics: Array, Greedy, Prefix Sum Solution Before diving into the detailed solution guide, I want to clarify one subtle point: the problem specifies that all subarrays with more than two elements must have a positive sum. This means the smallest subarray we need to consider is of length 3. This nuance is crucial for correctness. Here’s the comprehensive solution guide following your formatting rules....

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LeetCode 3513 - Number of Unique XOR Triplets I

LeetCode Problem 3513 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem asks us to determine the number of unique values that can result from taking the XOR of three elements in a given array nums , where the triplets (i, j, k) must satisfy i <= j <= k . Importantly, nums is a permutation of integers from 1 to n , meaning every integer...

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LeetCode 3512 - Minimum Operations to Make Array Sum Divisible by K

LeetCode Problem 3512 Difficulty: 🟢 Easy Topics: Array, Math Solution LeetCode 3512 - Minimum Operations to Make Array Sum Divisible by K Problem Understanding The problem gives us an integer array nums and an integer k . We are allowed to repeatedly perform one operation: choose any index i and decrease nums[i] by exactly 1 . Our goal is to determine the minimum number of such operations needed so that...

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LeetCode 3510 - Minimum Pair Removal to Sort Array II

LeetCode Problem 3510 Difficulty: 🔴 Hard Topics: Array, Hash Table, Linked List, Heap (Priority Queue), Simulation, Doubly-Linked List, Ordered Set Solution LeetCode 3510: Minimum Pair Removal to Sort Array II Problem Understanding We are given an array nums . The operation is highly constrained: Among all adjacent pairs, find the pair with the minimum sum. If multiple adjacent pairs have the same minimum sum, choose the leftmost one. Replace those...

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LeetCode 3509 - Maximum Product of Subsequences With an Alternating Sum Equal to K

LeetCode Problem 3509 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming Solution Problem Understanding The problem asks us to find a subsequence of a given integer array nums such that the alternating sum of the subsequence equals a target integer k , while maximizing the product of the numbers in that subsequence without exceeding a given limit . The alternating sum is defined as the sum of elements at...

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LeetCode 3508 - Implement Router

LeetCode Problem 3508 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Design, Queue, Ordered Set Solution Problem Understanding The problem is asking us to design a Router data structure to manage network packets efficiently under memory constraints. Each packet has three attributes: source , destination , and timestamp . The router has a memory limit , meaning it can store only a fixed number of packets. If a new...

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LeetCode 3507 - Minimum Pair Removal to Sort Array I

LeetCode Problem 3507 Difficulty: 🟢 Easy Topics: Array, Hash Table, Linked List, Heap (Priority Queue), Simulation, Doubly-Linked List, Ordered Set Solution LeetCode 3507 - Minimum Pair Removal to Sort Array I Problem Understanding We are given an array nums . At any step, we are not free to choose any adjacent pair. Instead, the operation is completely determined by the current state of the array: Find the adjacent pair whose...

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LeetCode 3493 - Properties Graph

LeetCode Problem 3493 Difficulty: 🟡 Medium Topics: Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Graph Theory Solution Problem Understanding The problem asks us to model a 2D array of integers, called properties , as an undirected graph. Each row of the array corresponds to a node in the graph. Two nodes are connected if the number of distinct integers they share is at least k . Our goal is...

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LeetCode 3501 - Maximize Active Section with Trade II

LeetCode Problem 3501 Difficulty: 🔴 Hard Topics: Array, String, Binary Search, Segment Tree Solution Problem Understanding The problem presents a binary string s where each character represents an active ( '1' ) or inactive ( '0' ) section. For each query, which specifies a substring of s , we are asked to determine the maximum number of active sections after performing at most one trade operation. A trade consists of...

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LeetCode 3500 - Minimum Cost to Divide Array Into Subarrays

LeetCode Problem 3500 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding This problem asks us to partition an array nums into contiguous subarrays, where each subarray contributes a weighted cost to the total. The cost for a subarray nums[l..r] depends on two components: the sum of the elements in the subarray, adjusted by a factor k multiplied by the order of the subarray, and the sum...

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LeetCode 3496 - Maximize Score After Pair Deletions

LeetCode Problem 3496 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3496 - Maximize Score After Pair Deletions Problem Understanding We are given an integer array nums . While the array contains more than two elements, we must repeatedly perform one of three operations: Remove the first two elements. Remove the last two elements. Remove the first and last element. Whenever we remove a pair, we add the sum of...

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LeetCode 3494 - Find the Minimum Amount of Time to Brew Potions

LeetCode Problem 3494 Difficulty: 🟡 Medium Topics: Array, Simulation, Prefix Sum Solution Problem Understanding The problem asks us to simulate a sequential brewing process for potions performed by a series of wizards. Each wizard has a skill level that determines the speed at which they brew a potion, while each potion has a mana requirement that affects how long it takes to brew. Specifically, the time for wizard i to...

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LeetCode 3491 - Phone Number Prefix

LeetCode Problem 3491 Difficulty: 🟢 Easy Topics: Array, String, Trie, Sorting Solution Problem Understanding The problem is asking us to determine whether any phone number in a given list is a prefix of another phone number. In simpler terms, if you have a list of strings representing numbers, you need to check that no string starts with another string from the list. If all numbers are independent prefixes, the output...

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LeetCode 3489 - Zero Array Transformation IV

LeetCode Problem 3489 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine the minimum number of sequential queries needed to transform an integer array nums into a Zero Array, where every element is zero. Each query specifies a subarray [li, ri] and a value vali , and the query allows us to decrement any subset of indices in that subarray by exactly vali...

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LeetCode 3488 - Closest Equal Element Queries

LeetCode Problem 3488 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search Solution Problem Understanding The problem asks us to process a series of queries on a circular array nums . Each query specifies an index, and for that index, we need to find the minimum circular distance to any other index with the same value. The circular distance means that after the last element, the array wraps back to...

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LeetCode 3486 - Longest Special Path II

LeetCode Problem 3486 Difficulty: 🔴 Hard Topics: Array, Hash Table, Tree, Depth-First Search, Prefix Sum Solution LeetCode 3486 - Longest Special Path II Problem Understanding We are given a rooted tree with n nodes. The tree is rooted at node 0 , and every edge has a positive length. Each node also contains a value stored in the array nums . A path is considered special if it satisfies two...

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LeetCode 3480 - Maximize Subarrays After Removing One Conflicting Pair

LeetCode Problem 3480 Difficulty: 🔴 Hard Topics: Array, Segment Tree, Enumeration, Prefix Sum Solution Here’s a detailed technical solution guide following your requested format for LeetCode 3480 - Maximize Subarrays After Removing One Conflicting Pair . Problem Understanding The problem gives you an integer n , which defines a sorted array nums = [1, 2, ..., n] . You are also given a list of conflictingPairs , each representing two...

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LeetCode 3484 - Design Spreadsheet

LeetCode Problem 3484 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design, Matrix Solution LeetCode 3484 - Design Spreadsheet Problem Understanding This problem asks us to design a very small spreadsheet system that supports three operations on cells and one operation for evaluating simple formulas. The spreadsheet always contains exactly 26 columns, labeled 'A' through 'Z' , and a configurable number of rows. Each cell can store an integer value....

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LeetCode 3476 - Maximize Profit from Task Assignment

LeetCode Problem 3476 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem asks us to assign tasks to workers in order to maximize total profit, under strict skill constraints. Each worker has a skill level, and each task has a required skill and an associated profit. A worker can only complete a task if their skill exactly matches the task's required skill. Additionally, there...

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LeetCode 3481 - Apply Substitutions

LeetCode Problem 3481 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort Solution LeetCode 3481 - Apply Substitutions Problem Understanding This problem gives us a collection of replacement rules and a text containing placeholders. Every placeholder has the format %X% , where X is a single uppercase letter corresponding to one of the replacement keys. The important detail is that replacement values may...

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LeetCode 3479 - Fruits Into Baskets III

LeetCode Problem 3479 Difficulty: 🟡 Medium Topics: Array, Binary Search, Segment Tree, Ordered Set Solution LeetCode 3479: Fruits Into Baskets III Problem Understanding This problem gives us two arrays of equal length: fruits[i] represents the quantity of the i-th fruit type. baskets[j] represents the capacity of the j-th basket. We process the fruit types from left to right. For each fruit quantity, we must place it into the leftmost available...

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LeetCode 3478 - Choose K Elements With Maximum Sum

LeetCode Problem 3478 Difficulty: 🟡 Medium Topics: Array, Sorting, Heap (Priority Queue) Solution Problem Understanding This problem asks us to compute a "maximum sum" for each index in an array based on a relationship with other elements. Specifically, for each index i in nums1 , we must consider all previous or other indices j where nums1[j] < nums1[i] , and then select up to k values from nums2[j] to maximize...

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LeetCode 3477 - Fruits Into Baskets II

LeetCode Problem 3477 Difficulty: 🟢 Easy Topics: Array, Binary Search, Segment Tree, Simulation, Ordered Set Solution Problem Understanding This problem asks us to simulate the placement of fruits into baskets following very specific rules. We are given two arrays of equal length, fruits and baskets . Each element in fruits represents the quantity of a fruit type, and each element in baskets represents the capacity of a basket. We need...

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LeetCode 3471 - Find the Largest Almost Missing Integer

LeetCode Problem 3471 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3471 - Find the Largest Almost Missing Integer Problem Understanding The problem gives us an integer array nums and an integer k . We consider every contiguous subarray of length k . An integer is called almost missing if it appears in exactly one of those size- k subarrays. Our goal is to find the largest integer that...

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LeetCode 3470 - Permutations IV

LeetCode Problem 3470 Difficulty: 🔴 Hard Topics: Array, Math, Combinatorics, Enumeration Solution LeetCode 3470 - Permutations IV Problem Understanding We are given two integers, n and k . We must consider all permutations of the numbers 1 through n that satisfy an alternating parity condition. In a valid permutation, every pair of adjacent elements must have different parity. In other words: Odd must be followed by even. Even must be...

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LeetCode 3469 - Find Minimum Cost to Remove Array Elements

LeetCode Problem 3469 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem is asking for the minimum total cost required to remove all elements from an integer array nums under a very specific set of operations. At each step, we can either remove any two elements from the first three elements of the array, and the cost for that operation is the maximum of the two elements...

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LeetCode 3467 - Transform Array by Parity

LeetCode Problem 3467 Difficulty: 🟢 Easy Topics: Array, Sorting, Counting Solution LeetCode 3467 - Transform Array by Parity Problem Understanding The problem gives us an integer array nums and asks us to transform it using three operations that must be performed in a specific order. First, every even number must be replaced with 0 . Second, every odd number must be replaced with 1 . After this transformation, the array...

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LeetCode 3459 - Length of Longest V-Shaped Diagonal Segment

LeetCode Problem 3459 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Memoization, Matrix Solution Problem Understanding We are given an n x m matrix whose entries are only 0 , 1 , or 2 . A valid V-shaped diagonal segment must satisfy two independent requirements: First, the values along the path must follow a very specific sequence. The first cell must contain 1 . Every subsequent cell must alternate between 2...

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LeetCode 3462 - Maximum Sum With at Most K Elements

LeetCode Problem 3462 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue), Matrix Solution Problem Understanding We are given a matrix grid , where each row contains a collection of values that can potentially be selected. We are also given an array limits , where limits[i] specifies the maximum number of elements that may be chosen from row i . The goal is to select at most k elements...

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LeetCode 3449 - Maximize the Minimum Game Score

LeetCode Problem 3449 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy Solution Problem Understanding You are given an array points , where points[i] is the amount added to gameScore[i] every time you land on index i . The player starts outside the array at position -1 . Each move changes the current position by exactly one: Moving right from i to i + 1 Moving left from i to i...

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LeetCode 3457 - Eat Pizzas!

LeetCode Problem 3457 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem presents an array pizzas of size n where each element represents the weight of a pizza. Every day, you must eat exactly 4 pizzas , and the total weight you gain from these 4 pizzas depends on whether the day is odd or even. On odd-numbered days, your weight gain is equal to the heaviest...

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LeetCode 3454 - Separate Squares II

LeetCode Problem 3454 Difficulty: 🔴 Hard Topics: Array, Binary Search, Segment Tree, Sweep Line Solution LeetCode 3454 - Separate Squares II Problem Understanding This problem asks us to find the smallest horizontal line y = H that divides the union area of a collection of axis-aligned squares into two equal halves. Each square is represented as: (xi, yi) = bottom-left corner li = side length Therefore, a square covers: x-range:...

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LeetCode 3450 - Maximum Students on a Single Bench

LeetCode Problem 3450 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem provides a list of student-seat assignments, where each entry has the form [student_id, bench_id] . Each pair indicates that a particular student is sitting on a particular bench. The goal is to determine which bench has the largest number of unique students sitting on it and return that count. The important detail is that a...

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LeetCode 3452 - Sum of Good Numbers

LeetCode Problem 3452 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3452 - Sum of Good Numbers Problem Understanding This problem gives us an integer array nums and an integer k . For every position i , we need to determine whether nums[i] is a good number. A number is considered good if it is strictly greater than the element located k positions to its left, nums[i - k] , when...

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LeetCode 3446 - Sort Matrix by Diagonals

LeetCode Problem 3446 Difficulty: 🟡 Medium Topics: Array, Sorting, Matrix Solution Problem Understanding We are given an n x n square matrix grid . Every cell belongs to exactly one top-left to bottom-right diagonal. Two cells (r1, c1) and (r2, c2) are on the same diagonal if r1 - c1 == r2 - c2 . The problem asks us to independently sort each diagonal, but the required sorting order depends...

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LeetCode 3447 - Assign Elements to Groups with Constraints

LeetCode Problem 3447 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem requires assigning elements from one array, elements , to groups defined by another array, groups , under a divisibility constraint. Specifically, for each group groups[i] , we must find the smallest index j in elements such that groups[i] % elements[j] == 0 . If no such element exists, we assign -1 for that group. Multiple...

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LeetCode 3444 - Minimum Increments for Target Multiples in an Array

LeetCode Problem 3444 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Number Theory, Bitmask Solution LeetCode 3444 - Minimum Increments for Target Multiples in an Array Problem Understanding We are given two arrays: nums , the array whose elements we are allowed to increase. target , a small array containing values that must each be represented by at least one multiple somewhere in the final version of nums...

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LeetCode 3440 - Reschedule Meetings for Maximum Free Time II

LeetCode Problem 3440 Difficulty: 🟡 Medium Topics: Array, Greedy, Enumeration Solution LeetCode 3440 - Reschedule Meetings for Maximum Free Time II Problem Understanding We are given an event that lasts from time 0 to eventTime . Inside this event there are n non-overlapping meetings, represented by the arrays startTime and endTime . The meeting at index i occupies the interval: [startTime[i], endTime[i]] The meetings are already sorted and non-overlapping, meaning:...

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LeetCode 3439 - Reschedule Meetings for Maximum Free Time I

LeetCode Problem 3439 Difficulty: 🟡 Medium Topics: Array, Greedy, Sliding Window Solution Problem Understanding We are given an event that runs from time 0 to eventTime . Inside this event there are n non-overlapping meetings, already arranged in chronological order. Each meeting i occupies the interval: [startTime[i], endTime[i]] The meetings do not overlap, and the input guarantees: endTime[i] <= startTime[i + 1] which means there may be free time between...

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LeetCode 3437 - Permutations III

LeetCode Problem 3437 Difficulty: 🟡 Medium Topics: Array, Backtracking Solution LeetCode 3437 - Permutations III Problem Understanding We are given a single integer n , and we need to generate all permutations of the numbers from 1 to n . However, not every permutation is valid. A permutation is considered an alternating permutation if every pair of adjacent elements has different parity. In other words: An odd number must always...

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LeetCode 3435 - Frequencies of Shortest Supersequences

LeetCode Problem 3435 Difficulty: 🔴 Hard Topics: Array, String, Bit Manipulation, Graph Theory, Topological Sort, Enumeration Solution Problem Understanding The problem asks us to find all shortest common supersequences (SCS) of a given list of two-character strings words . A shortest common supersequence is a string of minimum length that contains each word in words as a subsequence. Importantly, the output should not include SCSs that are permutations of each...

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LeetCode 3433 - Count Mentions Per User

LeetCode Problem 3433 Difficulty: 🟡 Medium Topics: Array, Math, Sorting, Simulation Solution LeetCode 3433 - Count Mentions Per User Problem Understanding This problem asks us to simulate a sequence of user activity events and count how many times each user is mentioned across all message events. We are given: numberOfUsers , the total number of users with IDs from 0 to numberOfUsers - 1 events , where each event is...

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LeetCode 3428 - Maximum and Minimum Sums of at Most Size K Subsequences

LeetCode Problem 3428 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Sorting, Combinatorics Solution Problem Understanding We are given an array nums and an integer k . For every subsequence whose size is at most k , we look at two values: The minimum element in that subsequence. The maximum element in that subsequence. We add minimum + maximum for every valid subsequence, then return the total modulo 10^9 +...

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LeetCode 3429 - Paint House IV

LeetCode Problem 3429 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem is asking us to paint n houses arranged in a line with three available colors for each house, minimizing the total painting cost while satisfying two constraints. The first constraint is the standard one from the classic "Paint House" problem: no two adjacent houses can have the same color. The second constraint is new and...

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LeetCode 3427 - Sum of Variable Length Subarrays

LeetCode Problem 3427 Difficulty: 🟢 Easy Topics: Array, Prefix Sum Solution Problem Understanding The problem provides an integer array nums of length n . For each index i , we are asked to consider a subarray that ends at i but starts at start = max(0, i - nums[i]) . This effectively means the subarray has a variable length depending on the value of nums[i] but never extends beyond the...

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LeetCode 3425 - Longest Special Path

LeetCode Problem 3425 Difficulty: 🔴 Hard Topics: Array, Hash Table, Tree, Depth-First Search, Prefix Sum Solution Problem Understanding This problem provides an undirected tree rooted at node 0 with n nodes and weighted edges, where each node has a value defined in the array nums . A special path is a downward path (from ancestor to descendant) such that all node values along the path are unique . The path...

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LeetCode 3424 - Minimum Cost to Make Arrays Identical

LeetCode Problem 3424 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to transform one integer array arr into another integer array brr with the minimum cost using two types of operations. The first operation allows splitting arr into contiguous subarrays and rearranging them at a fixed cost k per operation. The second operation allows adjusting any element by adding or subtracting a positive integer...

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LeetCode 3423 - Maximum Difference Between Adjacent Elements in a Circular Array

LeetCode Problem 3423 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3423 - Maximum Difference Between Adjacent Elements in a Circular Array Problem Understanding This problem gives us an integer array nums and asks us to find the largest absolute difference between any two adjacent elements. The important detail is that the array is circular . In a normal array, element i is adjacent only to elements i - 1 and...

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LeetCode 3422 - Minimum Operations to Make Subarray Elements Equal

LeetCode Problem 3422 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Sliding Window, Heap (Priority Queue) Solution LeetCode 3422 - Minimum Operations to Make Subarray Elements Equal Problem Understanding We are given an array nums and an integer k . In a single operation, we may increase or decrease any element by exactly 1 . Our goal is not to make the entire array equal. Instead, we only need at...

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LeetCode 3420 - Count Non-Decreasing Subarrays After K Operations

LeetCode Problem 3420 Difficulty: 🔴 Hard Topics: Array, Stack, Segment Tree, Queue, Sliding Window, Monotonic Stack, Monotonic Queue Solution Problem Understanding You are given an array nums and a budget of at most k increment operations. For any chosen subarray, you may repeatedly pick an element inside that subarray and increase it by 1 . The goal is to determine whether that subarray can be transformed into a non-decreasing array...

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LeetCode 3418 - Maximum Amount of Money Robot Can Earn

LeetCode Problem 3418 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding We are given an m x n grid where each cell contains either a positive value, zero, or a negative value. The robot starts at the top-left cell (0, 0) and must reach the bottom-right cell (m - 1, n - 1) . At every step it may only move either right or down, so every...

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LeetCode 3417 - Zigzag Grid Traversal With Skip

LeetCode Problem 3417 Difficulty: 🟢 Easy Topics: Array, Matrix, Simulation Solution LeetCode 3417 - Zigzag Grid Traversal With Skip Problem Understanding This problem asks us to traverse a two-dimensional grid in a zigzag order while visiting only every other cell in the traversal sequence. The zigzag traversal follows a very specific pattern: Start at the top-left corner (0, 0) . Traverse the first row from left to right. Move down...

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LeetCode 3416 - Subsequences with a Unique Middle Mode II

LeetCode Problem 3416 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Combinatorics Solution Problem Understanding We are given an array nums , and we must count how many subsequences of length exactly 5 have a very specific property. For any chosen subsequence $$[a,b,c,d,e]$$ the middle element is c , because it is the third element of a length-5 sequence. The subsequence is valid if: c is a mode of the...

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LeetCode 3413 - Maximum Coins From K Consecutive Bags

LeetCode Problem 3413 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sliding Window, Sorting, Prefix Sum Solution LeetCode 3413 - Maximum Coins From K Consecutive Bags Problem Understanding We are given several non-overlapping segments on a number line. Each segment [l, r, c] means that every bag at positions l, l+1, ..., r contains exactly c coins. All positions not covered by any segment contain 0 coins. The goal is...

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LeetCode 3411 - Maximum Subarray With Equal Products

LeetCode Problem 3411 Difficulty: 🟢 Easy Topics: Array, Math, Sliding Window, Enumeration, Number Theory Solution LeetCode 3411 - Maximum Subarray With Equal Products Problem Understanding We are given an array nums consisting of positive integers. For any array arr , define: prod(arr) as the product of all elements. gcd(arr) as the greatest common divisor of all elements. lcm(arr) as the least common multiple of all elements. A subarray is called...

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LeetCode 3409 - Longest Subsequence With Decreasing Adjacent Difference

LeetCode Problem 3409 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 3409 - Longest Subsequence With Decreasing Adjacent Difference Problem Understanding We are given an array nums , and we want to choose a subsequence from it. A subsequence preserves the original order of elements but may skip arbitrary positions. For a chosen subsequence $$seq_0, seq_1, seq_2, \dots, seq_m$$ we look at the absolute differences between consecutive elements: $$|seq_1-seq_0|,...

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LeetCode 3376 - Minimum Time to Break Locks I

LeetCode Problem 3376 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Breadth-First Search, Bitmask Solution LeetCode 3376 - Minimum Time to Break Locks I Problem Understanding The problem describes a sequence of locks that must all be broken. Each lock requires a certain amount of energy, given by strength[i] . Bob's sword starts with: Energy = 0 Growth factor x = 1 Every minute, the sword gains x...

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LeetCode 3183 - The Number of Ways to Make the Sum

LeetCode Problem 3183 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine the number of distinct ways to sum up to an integer n using a limited set of coins. Specifically, we have coins of value 1, 2, and 6 available in infinite quantities, and coins of value 4 with a strict limit of two. The key points are that the order of...

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LeetCode 1847 - Closest Room

LeetCode Problem 1847 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sorting, Ordered Set Solution LeetCode 1847: Closest Room Problem Understanding We are given a list of hotel rooms, where each room has: Problem Understanding The problem gives us a collection of hotel rooms, where each room has two attributes: A unique room ID A room size We are also given several queries. Each query contains: preferred : the room ID...

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LeetCode 3375 - Minimum Operations to Make Array Values Equal to K

LeetCode Problem 3375 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 3375 - Minimum Operations to Make Array Values Equal to K Problem Understanding The problem gives us an integer array nums and a target value k . Our goal is to transform the entire array so that every element becomes exactly equal to k . However, we cannot arbitrarily change values. Each operation follows a very specific rule....

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LeetCode 3224 - Minimum Array Changes to Make Differences Equal

LeetCode Problem 3224 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem gives us an integer array nums of even length n and an integer k . We are allowed to change any element in nums to any integer in the range [0, k] . Our goal is to ensure that for all symmetric pairs (nums[i], nums[n - i - 1]) , the absolute difference...

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LeetCode 3206 - Alternating Groups I

LeetCode Problem 3206 Difficulty: 🟢 Easy Topics: Array, Sliding Window Solution Problem Understanding The problem gives us a circular array called colors , where each element represents the color of a tile: 0 means red 1 means blue Because the tiles form a circle, the first and last tiles are considered adjacent. We need to count how many groups of exactly 3 contiguous tiles form an alternating group. A group...

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LeetCode 3176 - Find the Maximum Length of a Good Subsequence I

LeetCode Problem 3176 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming Solution Problem Understanding We are given an integer array nums and a non-negative integer k . We need to find the maximum possible length of a subsequence such that the number of adjacent unequal pairs is at most k . A subsequence is formed by deleting zero or more elements from the array without changing the order of...

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LeetCode 3151 - Special Array I

LeetCode Problem 3151 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to determine whether a given integer array is "special". An array is considered special if every pair of adjacent elements has different parity. Parity refers to whether a number is even or odd. Two numbers have different parity if one is even and the other is odd. For example: 2 and 5 have different parity...

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LeetCode 3108 - Minimum Cost Walk in Weighted Graph

LeetCode Problem 3108 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Union-Find, Graph Theory Solution Problem Understanding This problem gives us an undirected weighted graph with n vertices and up to 10^5 edges. Each edge connects two vertices and has an integer weight. For every query [s, t] , we must determine the minimum possible cost of any walk from node s to node t . The key detail is the...

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LeetCode 3074 - Apple Redistribution into Boxes

LeetCode Problem 3074 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to redistribute a collection of apple packs into boxes while using the minimum number of boxes . Each pack apple[i] contains a certain number of apples, and each box capacity[j] can hold up to a certain number of apples. Apples from a single pack can be split across multiple boxes, so we are...

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LeetCode 2976 - Minimum Cost to Convert String I

LeetCode Problem 2976 Difficulty: 🟡 Medium Topics: Array, String, Graph Theory, Shortest Path Solution Problem Understanding This problem asks us to transform one string into another while minimizing the total conversion cost. We are given two strings, source and target , both with the same length. Each position in source must eventually become the corresponding character in target . We are also given a list of allowed character transformations. A...

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LeetCode 2740 - Find the Value of the Partition

LeetCode Problem 2740 Difficulty: 🟡 Medium Topics: Array, Sorting Solution LeetCode 2740: Find the Value of the Partition Problem Understanding We are given an array nums containing positive integers. Our task is to divide all elements into two non-empty groups, nums1 and nums2 . Every element must belong to exactly one of the two groups, and neither group may be empty. For a particular partition, the value is defined as:...

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LeetCode 2527 - Find Xor-Beauty of Array

LeetCode Problem 2527 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem defines a special value called the "effective value" for every possible triplet of indices (i, j, k) in the array: $$((nums[i] \mid nums[j]) & nums[k])$$ where: | is the bitwise OR operator & is the bitwise AND operator The xor-beauty of the array is the XOR of the effective values for all possible triplets....

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LeetCode 2387 - Median of a Row Wise Sorted Matrix

LeetCode Problem 2387 Difficulty: 🟡 Medium Topics: Array, Binary Search, Matrix Solution LeetCode 2387. Median of a Row Wise Sorted Matrix Problem Understanding We are given an m × n matrix grid where every row is already sorted in non-decreasing order. The total number of elements in the matrix is guaranteed to be odd because both m and n are odd. The task is to find the median of all...

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LeetCode 1992 - Find All Groups of Farmland

LeetCode Problem 1992 Difficulty: 🟡 Medium Topics: Array, Depth-First Search, Breadth-First Search, Matrix Solution Problem Understanding In this problem, we are given a binary matrix called land . Each cell contains either: 0 , representing forest land 1 , representing farmland The farmland cells are organized into rectangular groups. Every group is guaranteed to form a perfect rectangle made entirely of 1 s. Additionally, different groups never touch each other...

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LeetCode 1913 - Maximum Product Difference Between Two Pairs

LeetCode Problem 1913 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding This problem asks us to find the maximum product difference between two pairs of numbers from a given array. Specifically, given an array nums , we need to select four distinct indices w, x, y, z to form two pairs (nums[w], nums[x]) and (nums[y], nums[z]) . The goal is to maximize the expression (nums[w] * nums[x]) - (nums[y]...

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LeetCode 1782 - Count Pairs Of Nodes

LeetCode Problem 1782 Difficulty: 🔴 Hard Topics: Array, Hash Table, Two Pointers, Binary Search, Graph Theory, Sorting, Counting Solution LeetCode 1782 - Count Pairs Of Nodes Problem Understanding We are given an undirected graph with n nodes and a list of edges. Multiple edges between the same pair of nodes are allowed. For any pair of nodes (a, b) , define incident(a, b) as the number of edges connected to...

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LeetCode 1851 - Minimum Interval to Include Each Query

LeetCode Problem 1851 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sweep Line, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us a collection of inclusive integer intervals and a list of query values. For every query, we must determine the size of the smallest interval that contains that query value. An interval [left, right] contains a query q if: left <= q <= right The size of an...

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LeetCode 2551 - Put Marbles in Bags

LeetCode Problem 2551 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem asks us to distribute weights.length marbles into k contiguous bags, where the cost of a bag is defined as the sum of the first and last marble in that bag. We are to calculate the difference between the maximum and minimum possible total scores across all valid distributions. The input weights is...

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LeetCode 2348 - Number of Zero-Filled Subarrays

LeetCode Problem 2348 Difficulty: 🟡 Medium Topics: Array, Math Solution Problem Understanding The problem asks us to count the number of contiguous subarrays in an integer array nums that consist entirely of zeros. A subarray is defined as any consecutive sequence of elements from the original array. The input array can contain any integers within the range -10^9 to 10^9 , and the array length can be up to 10^5...

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LeetCode 2460 - Apply Operations to an Array

LeetCode Problem 2460 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Simulation Solution LeetCode 2460 - Apply Operations to an Array Problem Understanding This problem gives us a 0-indexed array nums containing non-negative integers. We must perform a sequence of operations on adjacent elements, then rearrange the resulting array by moving all zeros to the end. The first phase consists of processing the array from left to right. For every index...

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LeetCode 3042 - Count Prefix and Suffix Pairs I

LeetCode Problem 3042 Difficulty: 🟢 Easy Topics: Array, String, Trie, Rolling Hash, String Matching, Hash Function Solution LeetCode 3042 - Count Prefix and Suffix Pairs I Problem Understanding The problem gives us an array of strings called words . For every pair of indices (i, j) where i < j , we must determine whether words[i] is both a prefix and a suffix of words[j] . A string is a...

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LeetCode 1902 - Depth of BST Given Insertion Order

LeetCode Problem 1902 Difficulty: 🟡 Medium Topics: Array, Tree, Binary Search Tree, Binary Tree, Ordered Set Solution Problem Understanding The problem gives us an array order that represents the exact sequence in which values are inserted into a binary search tree, usually abbreviated as BST. The array is a permutation of integers from 1 to n , which means every value appears exactly once and there are no duplicates. We...

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LeetCode 1993 - Operations on Tree

LeetCode Problem 1993 Difficulty: 🟡 Medium Topics: Array, Hash Table, Tree, Depth-First Search, Breadth-First Search, Design Solution LeetCode 1993 - Operations on Tree Problem Understanding The problem asks us to design a mutable tree-based data structure that supports three operations: lock , unlock , and upgrade . Each node in the tree may either be unlocked or locked by exactly one user. The operations must follow strict rules about when...

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LeetCode 1891 - Cutting Ribbons

LeetCode Problem 1891 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding The problem requires determining the maximum possible length x of ribbons such that, after cutting or keeping the given ribbons in the array ribbons , you can obtain at least k ribbons of length x . Each ribbon can be cut into smaller segments of positive integer length or left as-is, and any leftover pieces that do...

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LeetCode 3254 - Find the Power of K-Size Subarrays I

LeetCode Problem 3254 Difficulty: 🟡 Medium Topics: Array, Sliding Window Solution Problem Understanding The problem asks us to examine every contiguous subarray of length k in the input array nums and determine its "power". A subarray has valid power only if two conditions are simultaneously true: The elements are sorted in strictly ascending order. Every adjacent pair differs by exactly 1 , meaning the sequence is consecutive. If both conditions...

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LeetCode 2436 - Minimum Split Into Subarrays With GCD Greater Than One

LeetCode Problem 2436 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Greedy, Number Theory Solution Problem Understanding The problem requires splitting a given array of positive integers into contiguous subarrays such that the greatest common divisor (GCD) of each subarray is strictly greater than 1. The goal is to minimize the number of subarrays after splitting. In simpler terms, we need to partition the array into the fewest contiguous segments...

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LeetCode 3092 - Most Frequent IDs

LeetCode Problem 3092 Difficulty: 🟡 Medium Topics: Array, Hash Table, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem asks us to maintain a collection of IDs that is updated incrementally based on two arrays, nums and freq . Each index i represents a step. At step i , we either add freq[i] copies of nums[i] to the collection if freq[i] is positive, or remove -freq[i] copies of nums[i]...

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LeetCode 2948 - Make Lexicographically Smallest Array by Swapping Elements

LeetCode Problem 2948 Difficulty: 🟡 Medium Topics: Array, Union-Find, Sorting Solution Problem Understanding The problem asks us to transform a given array of positive integers nums into its lexicographically smallest form by performing a specific swap operation any number of times. The operation allows swapping any two elements nums[i] and nums[j] only if the absolute difference between them is at most limit . The lexicographically smallest array is one where,...

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LeetCode 1858 - Longest Word With All Prefixes

LeetCode Problem 1858 Difficulty: 🟡 Medium Topics: Array, String, Depth-First Search, Trie Solution Problem Understanding The problem gives us an array of lowercase strings called words . We need to find the longest word such that every prefix of that word also exists in the array. A prefix means the string formed by taking characters from the beginning of the word. For example, for "apple" : Length 1 prefix: "a"...

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LeetCode 2577 - Minimum Time to Visit a Cell In a Grid

LeetCode Problem 2577 Difficulty: 🔴 Hard Topics: Array, Breadth-First Search, Graph Theory, Heap (Priority Queue), Matrix, Shortest Path Solution That is a long, multi-section technical guide. To make sure I target the correct problem and avoid producing the wrong reference document, can you confirm the exact LeetCode problem number/title? You mentioned LeetCode 2577 - Minimum Time to Visit a Cell In a Grid . If that is correct, I will...

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LeetCode 2971 - Find Polygon With the Largest Perimeter

LeetCode Problem 2971 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Prefix Sum Solution LeetCode 2971 - Find Polygon With the Largest Perimeter Problem Understanding The problem gives us an array nums containing positive integers. Each integer represents a potential side length that we may use when constructing a polygon. A polygon must have at least three sides. The key geometric property we are given is that if the side lengths...

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LeetCode 2789 - Largest Element in an Array after Merge Operations

LeetCode Problem 2789 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us an array of positive integers and allows a special merge operation between adjacent elements. We may choose an index i such that: nums[i] <= nums[i + 1] When this condition is satisfied, we merge the two elements by adding nums[i] into nums[i + 1] , then removing nums[i] from the array. In effect, the...

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LeetCode 2545 - Sort the Students by Their Kth Score

LeetCode Problem 2545 Difficulty: 🟡 Medium Topics: Array, Sorting, Matrix Solution Problem Understanding In this problem, we are given a matrix named score with dimensions m x n . Each row represents a student, and each column represents an exam. The value score[i][j] is the score obtained by the i th student on the j th exam. The task is to sort the rows of the matrix according to the...

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LeetCode 3292 - Minimum Number of Valid Strings to Form Target II

LeetCode Problem 3292 Difficulty: 🔴 Hard Topics: Array, String, Binary Search, Dynamic Programming, Greedy, Segment Tree, Rolling Hash, String Matching, Hash Function Solution LeetCode 3292 - Minimum Number of Valid Strings to Form Target II Problem Understanding We are given a collection of strings words and a target string target . A string is considered valid if it is a prefix of at least one word in words . This...

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LeetCode 2549 - Count Distinct Numbers on Board

LeetCode Problem 2549 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Simulation Solution Problem Understanding The problem starts with a single integer n written on a board. Every day, we examine every number currently on the board. For each number x , we look for all integers i such that: 1 <= i <= n x % i == 1 Whenever such an integer i exists, we add it to...

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LeetCode 1975 - Maximum Matrix Sum

LeetCode Problem 1975 Difficulty: 🟡 Medium Topics: Array, Greedy, Matrix Solution Problem Understanding The problem gives an n x n integer matrix and allows an operation where we pick any two adjacent cells (sharing a side) and multiply both values by -1 . This operation can be applied any number of times, and the goal is to maximize the total sum of all matrix elements after any sequence of such...

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LeetCode 2975 - Maximum Square Area by Removing Fences From a Field

LeetCode Problem 2975 Difficulty: 🟡 Medium Topics: Array, Hash Table, Enumeration Solution Problem Understanding The field is represented as a large rectangle whose outer boundaries are fixed fences. Inside the field, additional horizontal and vertical fences divide the area into smaller sections. A horizontal fence spans the entire width of the field at a specific row coordinate, and a vertical fence spans the entire height of the field at a...

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LeetCode 2502 - Design Memory Allocator

LeetCode Problem 2502 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Simulation Solution Problem Understanding The problem requires designing a memory allocator that manages a fixed-size memory array. Initially, all memory units are free, and the allocator supports two operations: allocating a block of consecutive free memory units for a given ID ( mID ) and freeing all memory units associated with a given mID . Allocation should always select...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2347 - Best Poker Hand

LeetCode Problem 2347 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem gives us exactly five playing cards. Each card is represented by two pieces of information: ranks[i] represents the numerical rank of the card, from 1 to 13 suits[i] represents the suit of the card, using characters from 'a' to 'd' We need to determine the strongest poker hand that can be formed from these...

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LeetCode 2563 - Count the Number of Fair Pairs

LeetCode Problem 2563 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding The problem asks us to count how many pairs of indices (i, j) satisfy two conditions: i < j The sum nums[i] + nums[j] lies within the inclusive range [lower, upper] We are given an integer array nums and two bounds, lower and upper . The goal is to return the total number of...

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LeetCode 2216 - Minimum Deletions to Make Array Beautiful

LeetCode Problem 2216 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy Solution Problem Understanding The problem asks us to transform a given integer array nums into a beautiful array using the minimum number of deletions. A beautiful array satisfies two conditions: its length is even, and no two consecutive elements at even indices are equal ( nums[i] != nums[i + 1] for all i % 2 == 0 ). Deletions are...

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LeetCode 2407 - Longest Increasing Subsequence II

LeetCode Problem 2407 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Dynamic Programming, Binary Indexed Tree, Segment Tree, Queue, Monotonic Queue Solution Problem Understanding The problem asks us to find the length of the longest subsequence in an integer array nums such that the subsequence is strictly increasing and the difference between consecutive elements does not exceed a given integer k . A subsequence is formed by deleting zero or...

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LeetCode 2174 - Remove All Ones With Row and Column Flips II

LeetCode Problem 2174 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding The problem gives us an m x n binary matrix where every cell contains either 0 or 1 . Our goal is to remove all 1 s using the minimum number of operations. An operation can only be performed on a cell (i, j) that currently contains a 1 . Once we choose such...

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LeetCode 2561 - Rearranging Fruits

LeetCode Problem 2561 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Sort Solution Problem Understanding This problem gives us two arrays, basket1 and basket2 , where each element represents the cost of a fruit in a basket. Both baskets contain exactly n fruits. Our goal is to make the two baskets equal, where equality means that after sorting both arrays, they contain exactly the same multiset of values. We are...

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LeetCode 1855 - Maximum Distance Between a Pair of Values

LeetCode Problem 1855 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search Solution Problem Understanding You are given two integer arrays, nums1 and nums2 , and both arrays are sorted in non-increasing order. That means the values either stay the same or decrease as we move from left to right. A pair of indices (i, j) is considered valid if two conditions are satisfied: i <= j nums1[i] <= nums2[j]...

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LeetCode 3000 - Maximum Area of Longest Diagonal Rectangle

LeetCode Problem 3000 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3000 - Maximum Area of Longest Diagonal Rectangle Problem Understanding The input consists of a 2D array dimensions , where each element represents a rectangle. For a rectangle dimensions[i] , the value dimensions[i][0] is its length and dimensions[i][1] is its width. For every rectangle, we can compute the length of its diagonal using the Pythagorean theorem: $$\text{diagonal} = \sqrt{length^2 +...

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LeetCode 2746 - Decremental String Concatenation

LeetCode Problem 2746 Difficulty: 🟡 Medium Topics: Array, String, Dynamic Programming Solution LeetCode 2746 - Decremental String Concatenation Problem Understanding The problem gives us an array of strings words . We start with words[0] and then process the remaining strings one by one. For each new word words[i] , we have exactly two choices: Append it to the right side of the current string. Append it to the left side...

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LeetCode 2919 - Minimum Increment Operations to Make Array Beautiful

LeetCode Problem 2919 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to transform an input integer array nums into a beautiful array by performing a minimum number of increment operations. An increment operation increases a single element of nums by 1. The array is considered beautiful if every contiguous subarray of length 3 or more has a maximum element greater than or equal to...

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LeetCode 2294 - Partition Array Such That Maximum Difference Is K

LeetCode Problem 2294 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us an integer array nums and an integer k . We must divide the array into one or more subsequences such that every number belongs to exactly one subsequence, and for every subsequence, the difference between its maximum value and minimum value is at most k . The goal is to minimize the number...

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LeetCode 2470 - Number of Subarrays With LCM Equal to K

LeetCode Problem 2470 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 2470, Number of Subarrays With LCM Equal to K Problem Understanding The problem gives us an integer array nums and an integer k . We must count how many contiguous subarrays have a least common multiple, LCM, exactly equal to k . A subarray is any continuous segment of the array. For every possible subarray, we compute...

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LeetCode 3266 - Final Array State After K Multiplication Operations II

LeetCode Problem 3266 Difficulty: 🔴 Hard Topics: Array, Heap (Priority Queue), Simulation Solution LeetCode 3266 - Final Array State After K Multiplication Operations II Problem Understanding The problem gives us an integer array nums , an integer k , and an integer multiplier . We must perform exactly k operations on the array. In each operation, we locate the minimum value currently present in the array. If multiple elements share...

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LeetCode 1953 - Maximum Number of Weeks for Which You Can Work

LeetCode Problem 1953 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us an array called milestones , where each value represents how many milestones belong to a particular project. Every week, we must complete exactly one milestone from one project. However, there is an important restriction: we are not allowed to work on the same project in two consecutive weeks. Our goal is to determine the...

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LeetCode 2488 - Count Subarrays With Median K

LeetCode Problem 2488 Difficulty: 🔴 Hard Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding This problem asks us to count how many contiguous subarrays have a median equal to a given value k . The array nums contains every integer from 1 to n exactly once, which means all elements are distinct. That detail is extremely important because it removes ambiguity when comparing values relative to k . The...

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LeetCode 2426 - Number of Pairs Satisfying Inequality

LeetCode Problem 2426 Difficulty: 🔴 Hard Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution LeetCode 2426 - Number of Pairs Satisfying Inequality Problem Understanding We are given two integer arrays, nums1 and nums2 , of the same length n , along with an integer diff . We must count how many index pairs (i, j) satisfy both: i < j nums1[i]...

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LeetCode 2518 - Number of Great Partitions

LeetCode Problem 2518 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem requires us to partition an array of positive integers nums into two ordered groups such that the sum of elements in each group is at least k . A partition is considered great if this condition is satisfied. We are asked to return the number of distinct great partitions , modulo $10^9 + 7$. In...

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LeetCode 3323 - Minimize Connected Groups by Inserting Interval

LeetCode Problem 3323 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sliding Window, Sorting Solution Problem Understanding The problem asks us to minimize the number of connected groups in a set of intervals by adding exactly one interval of length at most k . Each interval [start, end] represents a continuous range on the number line. A connected group is a set of intervals that, taken together, form a continuous segment...

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LeetCode 3296 - Minimum Number of Seconds to Make Mountain Height Zero

LeetCode Problem 3296 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to calculate the minimum amount of time required for a team of workers to reduce the height of a mountain to zero, given that each worker has a specific time cost for performing work and the total work time grows linearly for consecutive units of height. Specifically, if...

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LeetCode 1914 - Cyclically Rotating a Grid

LeetCode Problem 1914 Difficulty: 🟡 Medium Topics: Array, Matrix, Simulation Solution LeetCode 1914 - Cyclically Rotating a Grid Problem Understanding The problem gives us an m x n matrix called grid , along with an integer k . Both dimensions of the matrix are guaranteed to be even numbers. The task is to rotate every layer of the matrix counter-clockwise exactly k times. A layer is the rectangular ring formed...

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LeetCode 1932 - Merge BSTs to Create Single BST

LeetCode Problem 1932 Difficulty: 🔴 Hard Topics: Array, Hash Table, Tree, Depth-First Search, Binary Search Tree, Binary Tree Solution Problem Understanding This problem asks us to take multiple very small binary search trees (BSTs), each with at most three nodes, and attempt to merge them into a single valid BST. Each tree is represented by its root node in the array trees . The only operation allowed is to attach...

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LeetCode 2942 - Find Words Containing Character

LeetCode Problem 2942 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding The problem asks us to process an array of lowercase strings words and a single lowercase character x , and return all indices of the words that contain this character. In simpler terms, for each string in the array, we must check whether x appears anywhere in that string. If it does, we record the index of that...

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LeetCode 2241 - Design an ATM Machine

LeetCode Problem 2241 Difficulty: 🟡 Medium Topics: Array, Greedy, Design Solution Problem Understanding The problem asks us to design a simulation of an ATM machine that can handle deposits and withdrawals with strict rules about how money is dispensed. The ATM stores five types of banknotes: $20, $50, $100, $200, and $500. The key challenge is implementing the withdrawal logic, which prioritizes giving out larger denominations first. The deposit function...

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LeetCode 2955 - Number of Same-End Substrings

LeetCode Problem 2955 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Counting, Prefix Sum Solution Problem Understanding The problem asks us to compute the number of same-end substrings within specified subranges of a given string s . A substring is same-end if its first and last character are identical. We are given multiple queries in the form [li, ri] , each representing a substring s[li..ri] . For each query, we...

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LeetCode 2898 - Maximum Linear Stock Score

LeetCode Problem 2898 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution LeetCode 2898 - Maximum Linear Stock Score Problem Understanding We are given a 1-indexed array prices , where prices[i] represents the stock price on day i . We want to choose a subsequence of indices, not necessarily contiguous, such that the selected indices satisfy a special linearity condition. For every pair of consecutive selected indices: $$prices[indexes[j]] - prices[indexes[j-1]] =...

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LeetCode 2496 - Maximum Value of a String in an Array

LeetCode Problem 2496 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding This problem asks us to compute the maximum value of strings in an array according to a specific definition of value. Each string can either be entirely numeric or alphanumeric. If a string consists only of digits, its value is the integer it represents. If it contains any letters, its value is the length of the string. We...

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LeetCode 3279 - Maximum Total Area Occupied by Pistons

LeetCode Problem 3279 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Simulation, Counting, Prefix Sum Solution Problem Understanding This problem is about simulating the motion of pistons in a car engine and computing the maximum total area under the pistons over time. Each piston moves either up or down by 1 unit every second, reversing direction when it hits the top ( height ) or bottom ( 0 ). The...

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LeetCode 1905 - Count Sub Islands

LeetCode Problem 1905 Difficulty: 🟡 Medium Topics: Array, Depth-First Search, Breadth-First Search, Union-Find, Matrix Solution Problem Understanding The problem presents two m x n binary matrices, grid1 and grid2 , representing maps of land ( 1 ) and water ( 0 ). Each matrix may contain multiple islands, where an island is defined as a connected group of 1 s that are adjacent vertically or horizontally . The task is...

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LeetCode 2786 - Visit Array Positions to Maximize Score

LeetCode Problem 2786 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem presents a 0-indexed array nums of integers and a positive integer x . You start at the first element, nums[0] , and can move to any subsequent position j where j > i . For each element you visit, you accumulate its value as part of your score. However, if the number at your current...

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LeetCode 1938 - Maximum Genetic Difference Query

LeetCode Problem 1938 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Depth-First Search, Trie Solution Problem Understanding The problem presents a rooted tree where each node is uniquely identified by an integer from 0 to n-1 . This integer also represents the genetic value of the node. The tree structure is given by the parents array, where parents[i] indicates the parent of node i , and -1 indicates the...

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LeetCode 2408 - Design SQL

LeetCode Problem 2408 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design Solution Problem Understanding This problem asks us to design a lightweight in memory database system that supports four core operations on multiple tables: Insert a row into a table Remove a row by id Select a single cell value Export all rows in CSV style format Each table has a fixed number of columns. The constructor receives two...

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LeetCode 1959 - Minimum Total Space Wasted With K Resizing Operations

LeetCode Problem 1959 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Prefix Sum Solution Let's go through a full, detailed technical solution guide for LeetCode 1959 following your formatting and style rules. Problem Understanding This problem asks us to minimize the total wasted space when resizing a dynamic array multiple times. We are given a 0-indexed array nums where nums[i] represents the number of elements that need to fit in the...

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LeetCode 3107 - Minimum Operations to Make Median of Array Equal to K

LeetCode Problem 3107 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to transform an integer array so that its median becomes exactly k , using the minimum number of operations. In one operation, we may either increase or decrease any single element by 1 . The median is defined after sorting the array in non-decreasing order. For arrays with odd length, the median is...

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LeetCode 2342 - Max Sum of a Pair With Equal Sum of Digits

LeetCode Problem 2342 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem requires finding the maximum sum of a pair of numbers in an array such that the sum of the digits of both numbers is equal. Specifically, you are given a 0-indexed array nums containing positive integers. You can choose two distinct indices i and j such that i != j ,...

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LeetCode 2683 - Neighboring Bitwise XOR

LeetCode Problem 2683 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem presents us with a binary array called derived of length n . This array is constructed from another binary array original of the same length using the bitwise XOR operation on adjacent elements. Specifically, each element derived[i] is the XOR of original[i] and original[i+1] , with a wrap-around at the end where derived[n-1] = original[n-1]...

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LeetCode 3112 - Minimum Time to Visit Disappearing Nodes

LeetCode Problem 3112 Difficulty: 🟡 Medium Topics: Array, Graph Theory, Heap (Priority Queue), Shortest Path Solution Problem Understanding The problem describes an undirected weighted graph with n vertices, represented by an array of edges. Each edge connects two vertices and has a weight. A walk is a sequence of vertices and edges that may revisit vertices or edges, and the cost of a walk is defined as the bitwise AND...

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LeetCode 2208 - Minimum Operations to Halve Array Sum

LeetCode Problem 2208 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding This problem asks us to repeatedly reduce numbers in an array until the total sum of the array has been reduced by at least half , while using the minimum number of operations . In one operation, we may choose any number currently in the array and replace it with exactly half of its value....

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LeetCode 2132 - Stamping the Grid

LeetCode Problem 2132 Difficulty: 🔴 Hard Topics: Array, Greedy, Matrix, Prefix Sum Solution Problem Understanding In this problem, we are given a binary matrix called grid . Every cell contains either: 0 , meaning the cell is empty 1 , meaning the cell is blocked or occupied We are also given a rectangular stamp with dimensions: stampHeight stampWidth The goal is to determine whether it is possible to place any...

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LeetCode 2707 - Extra Characters in a String

LeetCode Problem 2707 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Dynamic Programming, Trie Solution Problem Understanding The problem asks us to break a string s into non-overlapping substrings such that each substring exists in a given dictionary . Characters in s that cannot be matched with any dictionary word are considered extra characters . The goal is to find the minimum number of extra characters when splitting s optimally....

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LeetCode 3067 - Count Pairs of Connectable Servers in a Weighted Tree Network

LeetCode Problem 3067 Difficulty: 🟡 Medium Topics: Array, Tree, Depth-First Search Solution Problem Understanding The problem gives us a weighted tree representing servers connected by edges with weights. The servers are numbered from 0 to n-1 . Each edge has a weight representing distance or cost. We are asked to count, for each server c , the number of connectable server pairs (a, b) through c . A pair (a,...

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LeetCode 3155 - Maximum Number of Upgradable Servers

LeetCode Problem 3155 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search Solution Problem Understanding The problem requires calculating the maximum number of servers that can be upgraded at each data center independently, given the number of servers, upgrade costs, potential revenue from selling servers, and available money. Each data center has its own resources, and money cannot be transferred between them. For each data center, the input arrays provide: count[i]...

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LeetCode 2357 - Make Array Zero by Subtracting Equal Amounts

LeetCode Problem 2357 Difficulty: 🟢 Easy Topics: Array, Hash Table, Greedy, Sorting, Heap (Priority Queue), Simulation Solution LeetCode 2357 - Make Array Zero by Subtracting Equal Amounts Problem Understanding This problem gives us an array nums containing non-negative integers. We want to transform the entire array into zeros using a specific operation. In a single operation, we must choose a positive integer x that is less than or equal to...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1920 - Build Array from Permutation

LeetCode Problem 1920 Difficulty: 🟢 Easy Topics: Array, Simulation Solution LeetCode 1920, Build Array from Permutation Problem Understanding The problem gives us a zero-based permutation array called nums . A permutation means that every integer from 0 to n - 1 appears exactly once, where n is the length of the array. Since the array contains distinct values and covers the full range, every value in nums is also a...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1834 - Single-Threaded CPU

LeetCode Problem 1834 Difficulty: 🟡 Medium Topics: Array, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem asks us to simulate the execution of tasks on a single-threaded CPU . Each task has an enqueue time and a processing time . The CPU can process one task at a time and must select the next task according to two rules: first by shortest processing time , and then by smallest...

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LeetCode 3351 - Sum of Good Subsequences

LeetCode Problem 3351 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming Solution Problem Understanding This problem asks us to compute the sum of all good subsequences in a given integer array nums . A subsequence is any sequence derived from nums by deleting zero or more elements without changing the order of the remaining elements. A subsequence is considered good if the absolute difference between any two consecutive elements...

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LeetCode 2406 - Divide Intervals Into Minimum Number of Groups

LeetCode Problem 2406 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum Solution Problem Understanding The problem gives us a list of inclusive intervals, where each interval is represented as [left, right] . We must divide all intervals into groups such that no two intervals inside the same group intersect. The important detail is that the intervals are inclusive. This means two intervals overlap even...

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LeetCode 2875 - Minimum Size Subarray in Infinite Array

LeetCode Problem 2875 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window, Prefix Sum Solution LeetCode 2875 - Minimum Size Subarray in Infinite Array Problem Understanding This problem gives us a finite array nums , but asks us to imagine an infinite array called infinite_nums created by repeating nums forever. For example: nums = [1, 2, 3] infinite_nums = [1,2,3,1,2,3,1,2,3,1,2,3,...] We must find the shortest contiguous subarray in this infinite...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2915 - Length of the Longest Subsequence That Sums to Target

LeetCode Problem 2915 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 2915 - Length of the Longest Subsequence That Sums to Target Problem Understanding The problem gives us an array nums and an integer target . We must find a subsequence whose elements add up exactly to target , while maximizing the number of elements included in that subsequence. A subsequence is formed by deleting zero or more elements...

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LeetCode 2098 - Subsequence of Size K With the Largest Even Sum

LeetCode Problem 2098 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to find the largest possible even sum of a subsequence of length k from a given integer array nums . A subsequence is a sequence that can be obtained by deleting some elements from the array without changing the relative order of the remaining elements. The input consists of an array of integers...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2678 - Number of Senior Citizens

LeetCode Problem 2678 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding This problem asks us to count the number of passengers in a list who are strictly older than 60. Each passenger's information is compressed into a fixed-length string of 15 characters. The string is structured as follows: the first ten characters represent the phone number, the eleventh character represents gender, the twelfth and thirteenth characters represent the age,...

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LeetCode 3200 - Maximum Height of a Triangle

LeetCode Problem 3200 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 3200 - Maximum Height of a Triangle Problem Understanding The problem gives us two integers, red and blue , representing the number of red and blue balls available. We want to build a triangle where: Row 1 contains exactly 1 ball Row 2 contains exactly 2 balls Row 3 contains exactly 3 balls And so on There are two...

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LeetCode 3309 - Maximum Possible Number by Binary Concatenation

LeetCode Problem 3309 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Enumeration Solution Problem Understanding The problem is asking for the maximum integer value that can be created by concatenating the binary representations of all elements in a list of three integers. Each number should be converted to its binary representation without leading zeros. After conversion, the binary strings can be concatenated in any order. The resulting binary string should then...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2576 - Find the Maximum Number of Marked Indices

LeetCode Problem 2576 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Greedy, Sorting Solution Problem Understanding This problem asks us to maximize the number of indices in an array that can be "marked" using a specific operation. You are given an integer array nums and can repeatedly pick two different unmarked indices i and j such that 2 * nums[i] <= nums[j] . Once selected, both indices i and...

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LeetCode 3002 - Maximum Size of a Set After Removals

LeetCode Problem 3002 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution Problem Understanding The problem is asking us to maximize the number of unique elements we can have in a set after removing exactly half of the elements from two arrays nums1 and nums2 . Each array is of even length n , and after removing n/2 elements from each, we insert all remaining elements into a set. Since...

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LeetCode 2906 - Construct Product Matrix

LeetCode Problem 2906 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution Problem Understanding The problem asks us to construct a new matrix p from a given matrix grid . For every position (i, j) , the value p[i][j] must equal the product of every element in the matrix except grid[i][j] , and the result must be taken modulo 12345 . In other words, if the matrix contains k =...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2251 - Number of Flowers in Full Bloom

LeetCode Problem 2251 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Sorting, Prefix Sum, Ordered Set Solution Problem Understanding The problem asks us to determine, for a list of people arriving at certain times, how many flowers are in full bloom at the time of their arrival. Each flower has a start and end time representing the period it is in full bloom, inclusive of both endpoints. The input...

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LeetCode 3096 - Minimum Levels to Gain More Points

LeetCode Problem 3096 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding This problem is asking us to determine the minimum number of levels Alice should play in order to score more points than Bob , given that both play optimally and that some levels may be impossible to clear. The input is a binary array possible of length n . A 1 indicates a level can always be...

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LeetCode 2089 - Find Target Indices After Sorting Array

LeetCode Problem 2089 Difficulty: 🟢 Easy Topics: Array, Binary Search, Sorting Solution LeetCode 2089, Find Target Indices After Sorting Array Problem Understanding The problem gives us an integer array nums and an integer target . We must sort the array in non-decreasing order and then return every index where the value equals target . A target index is simply an index i such that: $nums[i] = target$ The important detail...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1964 - Find the Longest Valid Obstacle Course at Each Position

LeetCode Problem 1964 Difficulty: 🔴 Hard Topics: Array, Binary Search, Binary Indexed Tree Solution LeetCode 1964, Find the Longest Valid Obstacle Course at Each Position Problem Understanding The problem gives an array obstacles , where each value represents the height of an obstacle. For every position i , we must determine the length of the longest valid obstacle course that ends exactly at index i . A valid obstacle course...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2610 - Convert an Array Into a 2D Array With Conditions

LeetCode Problem 2610 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem asks us to transform a one-dimensional integer array nums into a two-dimensional array (a list of lists) while satisfying three specific conditions. First, every element from nums must appear in the 2D array exactly as many times as it appears in the original array. Second, each row of the 2D array must contain only distinct...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1877 - Minimize Maximum Pair Sum in Array

LeetCode Problem 1877 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding The problem asks us to pair elements in an array of even length such that the largest sum among all pairs is minimized. In simpler terms, imagine we have a collection of numbers and we want to form pairs of two numbers each. Each number can only belong to one pair. Once we pair them,...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2455 - Average Value of Even Numbers That Are Divisible by Three

LeetCode Problem 2455 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to calculate the average of all integers in an array nums that satisfy two conditions simultaneously: they must be even and divisible by 3 . In other words, we only consider numbers that are multiples of 6, because a number divisible by both 2 and 3 is divisible by 6. The input is a...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2735 - Collecting Chocolates

LeetCode Problem 2735 Difficulty: 🟡 Medium Topics: Array, Enumeration Solution LeetCode 2735 - Collecting Chocolates Problem Understanding The problem gives us an array nums , where nums[i] represents the cost of buying a chocolate currently located at index i . Initially, the chocolate at index i is also considered to be of type i . Since there are n positions, there are exactly n chocolate types. The goal is to...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3131 - Find the Integer Added to Array I

LeetCode Problem 3131 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3131 - Find the Integer Added to Array I Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , which have the same length. We are told that every element in nums1 was modified by adding the same integer x , and after this transformation the resulting array became equal to nums2 . The word "equal" here...

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LeetCode 3139 - Minimum Cost to Equalize Array

LeetCode Problem 3139 Difficulty: 🔴 Hard Topics: Array, Greedy, Enumeration Solution Problem Understanding This problem asks us to determine the minimum cost to make all elements in an array equal. You are allowed two types of operations: increment a single element at a cost of cost1 , or increment any two distinct elements simultaneously at a cost of cost2 . The goal is to compute the cheapest sequence of these...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2552 - Count Increasing Quadruplets

LeetCode Problem 2552 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Binary Indexed Tree, Enumeration, Prefix Sum Solution Problem Understanding The problem asks us to count the number of increasing quadruplets (i, j, k, l) in a 0-indexed array nums of size n , where nums is a permutation of the integers from 1 to n . A quadruplet is considered increasing if it satisfies both the index order 0 <=...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2653 - Sliding Subarray Beauty

LeetCode Problem 2653 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution Problem Understanding The problem asks us to compute the beauty of every contiguous subarray of size k within a given integer array nums . The beauty of a subarray is defined as the xth smallest negative number in that subarray. If a subarray contains fewer than x negative numbers, the beauty is 0 . In simpler terms,...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3232 - Find if Digit Game Can Be Won

LeetCode Problem 3232 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem presents a simple two-player game between Alice and Bob using an array of positive integers. Each number in the array is either a single-digit number (1 to 9) or a double-digit number (10 to 99). Alice has the choice to select either all single-digit numbers or all double-digit numbers from the array, while Bob automatically gets...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2340 - Minimum Adjacent Swaps to Make a Valid Array

LeetCode Problem 2340 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Exploration The previous solution fails immediately under a counterexample check. The proposed path was the union of the segments from $A$ to the midpoints of $AB$ and $AC$. If the side length is $a$, then the detector radius is $$r=\frac h2=\frac{\sqrt3}{4}a.$$ The distance from $B$ to that path is $a/2$, while $$\frac a2>\frac{\sqrt3}{4}a=r.$$ Hence $B$ is not detected at all....

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2418 - Sort the People

LeetCode Problem 2418 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Sorting Solution LeetCode 2418, Sort the People Problem Understanding This problem gives us two arrays of equal length: names[i] represents the name of a person heights[i] represents the height of that same person The two arrays are aligned by index, meaning the person at index i has both the name names[i] and the height heights[i] . The goal is...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1893 - Check if All the Integers in a Range Are Covered

LeetCode Problem 1893 Difficulty: 🟢 Easy Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to determine whether every integer within a given inclusive range [left, right] is covered by at least one of the intervals specified in the ranges array. Each element of ranges is itself an array [starti, endi] representing an inclusive interval, meaning the integers starti and endi are part of the interval....

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3233 - Find the Count of Numbers Which Are Not Special

LeetCode Problem 3233 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution Problem Understanding The problem asks us to count how many integers in the inclusive range [l, r] are not special . A number is considered special if it has exactly two proper divisors. A proper divisor of a number x is any positive divisor of x other than x itself. For example: Proper divisors of 4 are 1...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2307 - Check for Contradictions in Equations

LeetCode Problem 2307 Difficulty: 🔴 Hard Topics: Array, Depth-First Search, Union-Find, Graph Theory Solution Problem Understanding This problem gives us a collection of equations of the form: $$A_i / B_i = value_i$$ Each variable is represented as a string, and each equation defines a multiplicative relationship between two variables. The task is to determine whether all equations can simultaneously be true. If at least one equation conflicts with the others,...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2862 - Maximum Element-Sum of a Complete Subset of Indices

LeetCode Problem 2862 Difficulty: 🔴 Hard Topics: Array, Math, Number Theory Solution LeetCode 2862 - Maximum Element-Sum of a Complete Subset of Indices Problem Understanding The array nums is 1-indexed , meaning the first element corresponds to index 1 , the second element corresponds to index 2 , and so on. We want to select a subset of indices such that for every pair of selected indices i and j...

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LeetCode 3349 - Adjacent Increasing Subarrays Detection I

LeetCode Problem 3349 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us an integer array nums and an integer k . We need to determine whether the array contains two adjacent subarrays, each of length k , such that both subarrays are strictly increasing. A subarray is strictly increasing if every element is larger than the one before it. For example, [2, 5, 7] is strictly increasing...

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LeetCode 2916 - Subarrays Distinct Element Sum of Squares II

LeetCode Problem 2916 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem asks us to consider every possible non-empty subarray of the input array nums . For each subarray, we compute how many distinct values appear inside it. We then square that distinct count, and finally sum the squared values across all subarrays. Formally, if a subarray contains k distinct elements, then...

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LeetCode 2050 - Parallel Courses III

LeetCode Problem 2050 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Graph Theory, Topological Sort Solution Problem Understanding The problem asks us to determine the minimum number of months required to complete all courses given prerequisite relationships and the time each course takes. Each course is labeled from 1 to n , and relations describes which courses must be completed before others. The time array provides the duration of each course,...

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LeetCode 3009 - Maximum Number of Intersections on the Chart

LeetCode Problem 3009 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Binary Indexed Tree, Geometry, Sweep Line, Sorting Solution I can provide the full guide, but I want to avoid giving you a technically incorrect reference document. For LeetCode 3009 , there are two subtly different interpretations that materially change the optimal algorithm and correctness proof: whether intersections at a chart vertex (k, y[k]) count once or twice when both...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2144 - Minimum Cost of Buying Candies With Discount

LeetCode Problem 2144 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding This problem asks us to minimize the total amount of money spent when buying candies under a special discount rule. For every two candies that are purchased, we may take one additional candy for free. However, the free candy must have a cost less than or equal to the cheaper of the two purchased candies. The input...

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LeetCode 2261 - K Divisible Elements Subarrays

LeetCode Problem 2261 Difficulty: 🟡 Medium Topics: Array, Hash Table, Trie, Rolling Hash, Hash Function, Enumeration Solution Problem Understanding This problem requires counting the number of distinct subarrays of a given integer array nums that satisfy a specific constraint: each subarray can contain at most k elements divisible by p . A subarray is a contiguous slice of the array, and "distinct" means either differing in length or differing in...

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LeetCode 3038 - Maximum Number of Operations With the Same Score I

LeetCode Problem 3038 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding The problem asks us to repeatedly perform an operation on an integer array nums . In each operation, we remove the first two elements of the array and compute a score , which is simply the sum of those two removed values. The key restriction is that every operation must have the exact same score . We are...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2151 - Maximum Good People Based on Statements

LeetCode Problem 2151 Difficulty: 🔴 Hard Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to determine the maximum number of good people in a group given a set of statements about each other. Each person can either be good (always tells the truth) or bad (may lie or tell the truth). The input is a square 2D array statements of size n x n ,...

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LeetCode 2397 - Maximum Rows Covered by Columns

LeetCode Problem 2397 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Matrix, Enumeration Solution Problem Understanding This problem asks us to maximize the number of rows covered in a binary matrix after selecting exactly numSelect columns. Each row is covered if all 1 s in that row are located in the selected columns, or if the row contains only 0 s. The input is an m x n binary matrix,...

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LeetCode 1916 - Count Ways to Build Rooms in an Ant Colony

LeetCode Problem 1916 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Tree, Depth-First Search, Graph Theory, Topological Sort, Combinatorics Solution Problem Understanding The problem asks us to count the number of valid ways to sequentially build all rooms in an ant colony, given a dependency tree that dictates which rooms must be built before others. Each room i has a predecessor prevRoom[i] that must be built before i . Room...

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3357 - Minimize the Maximum Adjacent Element Difference

LeetCode Problem 3357 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy Solution Problem Understanding The problem gives us an integer array nums , where some positions contain -1 . These -1 values represent missing elements that must be replaced. The key restriction is that we are allowed to choose exactly two positive integers, x and y , one time globally for the entire array. Every missing value must then be...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2215 - Find the Difference of Two Arrays

LeetCode Problem 2215 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 2215, Find the Difference of Two Arrays Problem Understanding This problem asks us to compare two integer arrays and identify the unique values that appear in one array but not the other. We are given two 0-indexed integer arrays, nums1 and nums2 . The goal is to return a list containing two separate lists: The first list should...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2345 - Finding the Number of Visible Mountains

LeetCode Problem 2345 Difficulty: 🟡 Medium Topics: Array, Stack, Sorting, Monotonic Stack Solution LeetCode 2345 - Finding the Number of Visible Mountains Problem Understanding Each mountain is represented by a peak point (x, y) . Because the mountain is a right-angled isosceles triangle with slopes +1 and -1 , its shape is completely determined by its peak. For a mountain with peak (x, y) : The left boundary touches the...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2557 - Maximum Number of Integers to Choose From a Range II

LeetCode Problem 2557 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution Problem Understanding The problem is asking to select the maximum number of integers from the range [1, n] under several constraints. First, integers in the banned array cannot be chosen. Second, each integer can be chosen at most once. Third, the sum of all chosen integers must not exceed maxSum . The goal is to determine the...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2039 - The Time When the Network Becomes Idle

LeetCode Problem 2039 Difficulty: 🟡 Medium Topics: Array, Breadth-First Search, Graph Theory Solution Problem Understanding This problem involves a network of servers where server 0 is the master and all other servers are data servers. Each data server initially sends a message to the master, and the master instantly responds upon receiving the message. The data servers resend messages periodically if they have not received a reply, according to the...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2846 - Minimum Edge Weight Equilibrium Queries in a Tree

LeetCode Problem 2846 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding You are given an undirected weighted tree with n nodes. Since the graph is a tree, there is exactly one simple path between any two nodes. Each edge has a weight between 1 and 26 . For every query [a, b] , we look at the unique path from node a to...

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3036 - Number of Subarrays That Match a Pattern II

LeetCode Problem 3036 Difficulty: 🔴 Hard Topics: Array, Rolling Hash, String Matching, Hash Function Solution This guide will be very long, likely exceeding a single message cleanly while still maintaining the level of detail and formatting quality you requested for a reference document. I can provide the complete guide in full , including: Problem Understanding Approaches (Brute Force + Optimal KMP) Algorithm Walkthrough Python Solution Go Solution Worked Examples (step-by-step...

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LeetCode 2087 - Minimum Cost Homecoming of a Robot in a Grid

LeetCode Problem 2087 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us a robot located on a two dimensional grid. The robot starts at startPos = [startrow, startcol] and wants to reach homePos = [homerow, homecol] . The robot can move one cell at a time in four directions: up, down, left, and right. Unlike a standard shortest path problem where every move has the same...

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LeetCode 3386 - Button with Longest Push Time

LeetCode Problem 3386 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us a sequence of keyboard button press events. Each event is represented as: [index, time] Here: index is the identifier of the button that was pressed. time is the moment when the press happened. The events are already sorted by increasing time, which is extremely important because it means we can process the presses in chronological...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2127 - Maximum Employees to Be Invited to a Meeting

LeetCode Problem 2127 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Depth-First Search, Graph Theory, Topological Sort Solution Problem Understanding This problem describes a group of employees sitting around a circular table. Every employee has exactly one favorite coworker, represented by the array favorite , where favorite[i] is the person employee i wants to sit next to. An employee will attend the meeting only if they can sit directly adjacent to...

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LeetCode 2088 - Count Fertile Pyramids in a Land

LeetCode Problem 2088 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem gives us a binary matrix where each cell represents a piece of land. A value of 1 means the land is fertile, while 0 means barren. We need to count every valid pyramidal plot and inverse pyramidal plot formed entirely from fertile cells. A normal pyramid points downward. Its apex is the top cell,...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2741 - Special Permutations

LeetCode Problem 2741 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to count the number of special permutations of a given array of distinct positive integers nums . A permutation is special if, for every adjacent pair of elements nums[i] and nums[i+1] , one element divides the other evenly, that is, either nums[i] % nums[i+1] == 0 or nums[i+1] % nums[i]...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2943 - Maximize Area of Square Hole in Grid

LeetCode Problem 2943 Difficulty: 🟡 Medium Topics: Array, Sorting Solution LeetCode 2943 - Maximize Area of Square Hole in Grid Problem Understanding The grid is formed by n + 2 horizontal bars and m + 2 vertical bars. These bars divide the plane into unit squares. The bars are numbered starting from 1 . Some horizontal bars listed in hBars may be removed, and some vertical bars listed in vBars...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2497 - Maximum Star Sum of a Graph

LeetCode Problem 2497 Difficulty: 🟡 Medium Topics: Array, Greedy, Graph Theory, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us an undirected graph where each node has an associated integer value. We are asked to form a star graph and compute the maximum possible star sum. A star graph is defined by choosing one node as the center and selecting up to k of its neighbors. The resulting...

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LeetCode 2008 - Maximum Earnings From Taxi

LeetCode Problem 2008 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Dynamic Programming, Sorting Solution Problem Understanding The problem describes a taxi traveling along a one directional road from point 1 to point n . Along the way, passengers request rides. Each ride is represented as [start, end, tip] , meaning the passenger wants to travel from start to end and will additionally pay a tip. If we accept...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2201 - Count Artifacts That Can Be Extracted

LeetCode Problem 2201 Difficulty: 🟡 Medium Topics: Array, Hash Table, Simulation Solution Problem Understanding This problem models an excavation process on a square n x n grid. Several rectangular artifacts are buried in the grid, and each artifact occupies one or more cells. Every artifact is described by four integers: (r1, c1) represents the top-left corner (r2, c2) represents the bottom-right corner This means the artifact occupies every cell inside...

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LeetCode 2416 - Sum of Prefix Scores of Strings

LeetCode Problem 2416 Difficulty: 🔴 Hard Topics: Array, String, Trie, Counting Solution Problem Understanding The problem is asking us to compute a special score for each string in a list of strings. Specifically, for a string term , its score is defined as the number of strings in the array that have term as a prefix. The main task is to compute, for each string in the list, the sum...

Practice › LeetCode › LeetCode 34xx ›

LeetCode 3400 - Maximum Number of Matching Indices After Right Shifts

LeetCode Problem 3400 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Simulation Solution Problem Understanding The problem gives us two arrays, nums1 and nums2 , both of the same length n . We are allowed to repeatedly perform a right circular shift on nums1 . A right shift moves every element one position to the right, and the last element wraps around to the beginning. For example: [1, 2, 3, 4]...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2917 - Find the K-or of an Array

LeetCode Problem 2917 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution LeetCode 2917 - Find the K-or of an Array Problem Understanding This problem introduces a generalized version of the bitwise OR operation called the K-or . In a normal bitwise OR, a bit in the result becomes 1 if at least one number has that bit set. The K-or operation changes this rule. Instead of requiring one occurrence, a...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2606 - Find the Substring With Maximum Cost

LeetCode Problem 2606 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Dynamic Programming Solution Problem Understanding The problem asks us to find the substring of a given string s that maximizes a custom cost function. Each character in the string has a value: if it exists in the string chars , its value is taken from the corresponding index in the array vals ; if it does not exist in...

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LeetCode 2731 - Movement of Robots

LeetCode Problem 2731 Difficulty: 🟡 Medium Topics: Array, Brainteaser, Sorting, Prefix Sum Solution LeetCode 2731 - Movement of Robots Problem Understanding The problem gives us a list of robots positioned on an infinite number line. Each robot starts at a unique coordinate from the array nums , and each robot has an associated movement direction from the string s . A robot moves exactly one unit per second. If the...

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LeetCode 2967 - Minimum Cost to Make Array Equalindromic

LeetCode Problem 2967 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Sorting Solution LeetCode 2967 - Minimum Cost to Make Array Equalindromic Problem Understanding We are given an integer array nums . We may repeatedly choose any element and replace it with any positive integer x . Replacing a value nums[i] with x costs |nums[i] - x| . The goal is to transform the array so that every element...

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LeetCode 2263 - Make Array Non-decreasing or Non-increasing

LeetCode Problem 2263 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to transform a given integer array nums into either a non-decreasing or a non-increasing array with the minimum number of operations. Each operation allows increasing or decreasing an element by exactly 1. A non-decreasing array is one in which every element is greater than or equal to the previous...

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LeetCode 2997 - Minimum Number of Operations to Make Array XOR Equal to K

LeetCode Problem 2997 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding This problem asks us to transform an array so that the bitwise XOR of all elements becomes exactly k , while minimizing the number of operations. An operation consists of selecting any element in the array and flipping exactly one bit in its binary representation. A bit flip changes a 0 to 1 or a 1 to...

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LeetCode 3371 - Identify the Largest Outlier in an Array

LeetCode Problem 3371 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting, Enumeration Solution Problem Understanding The problem gives us an integer array nums containing exactly three types of elements: n - 2 special numbers One element equal to the sum of all special numbers One outlier The task is to return the largest possible value that could serve as the outlier. The important detail is that these roles are determined...

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LeetCode 2065 - Maximum Path Quality of a Graph

LeetCode Problem 2065 Difficulty: 🔴 Hard Topics: Array, Backtracking, Graph Theory Solution Problem Understanding We are given an undirected weighted graph where each node has an associated value. A path is considered valid if: It starts at node 0 It ends at node 0 The total travel time does not exceed maxTime The important detail is that nodes may be revisited multiple times, but each node's value contributes to the...

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LeetCode 2956 - Find Common Elements Between Two Arrays

LeetCode Problem 2956 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding This problem asks us to compare two integer arrays and count how many elements from one array appear in the other. More specifically, we need to compute two values: answer1 is the number of indices i in nums1 such that nums1[i] appears at least once in nums2 . answer2 is the number of indices i in nums2...

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LeetCode 2865 - Beautiful Towers I

LeetCode Problem 2865 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution Problem Understanding The problem asks us to transform an array of tower heights into a mountain-shaped arrangement while removing as few bricks as necessary. A mountain-shaped arrangement is defined as one where tower heights first non-decrease up to a peak (or consecutive peaks of the same height) and then non-increase after the peak. We are not allowed to...

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LeetCode 2393 - Count Strictly Increasing Subarrays

LeetCode Problem 2393 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming Solution Problem Understanding The problem asks us to count all strictly increasing subarrays in a given array nums of positive integers. A strictly increasing subarray is a contiguous sequence of numbers where each element is strictly larger than the previous one. The output should be a single integer representing the total number of such subarrays. The input nums is...

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LeetCode 2547 - Minimum Cost to Split an Array

LeetCode Problem 2547 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Counting Solution Problem Understanding The problem asks us to split the array nums into one or more contiguous non-empty subarrays such that the total cost is minimized. For every subarray, we define a special quantity called its importance value. To compute it, we first construct the trimmed version of the subarray by removing every element that appears exactly...

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LeetCode 3300 - Minimum Element After Replacement With Digit Sum

LeetCode Problem 3300 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem asks us to transform an array of integers nums by replacing each element with the sum of its digits . After this transformation, we need to determine the minimum element in the resulting array. The input array nums consists of 1 to 100 elements, and each element ranges from 1 to 10,000. The constraints ensure that...

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LeetCode 2126 - Destroying Asteroids

LeetCode Problem 2126 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding In this problem, we are given the starting mass of a planet and a list of asteroid masses. The planet can collide with the asteroids in any order we choose. Every time the planet collides with an asteroid, one of two things happens: If the planet's current mass is greater than or equal to the asteroid's mass,...

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LeetCode 1961 - Check If String Is a Prefix of Array

LeetCode Problem 1961 Difficulty: 🟢 Easy Topics: Array, Two Pointers, String Solution Problem Understanding The problem is asking us to determine whether a given string s can be formed by concatenating the first k elements of an array words , where k is some positive integer less than or equal to the length of words . In other words, s must match exactly the prefix of the array when all...

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LeetCode 3382 - Maximum Area Rectangle With Point Constraints II

LeetCode Problem 3382 Difficulty: 🔴 Hard Topics: Array, Math, Binary Indexed Tree, Segment Tree, Geometry, Sorting Solution Problem Understanding The problem asks us to find the maximum area rectangle that can be formed from a given set of points on a 2D plane, under strict constraints. Each rectangle must have its edges parallel to the x and y axes, must use exactly four points from the input as corners, and...

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LeetCode 2412 - Minimum Money Required Before Transactions

LeetCode Problem 2412 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the minimum initial money required to complete all transactions in any order . Each transaction is defined by [costi, cashbacki] , meaning that performing the transaction requires at least costi money, and after completing it, we receive cashbacki back. In other words, we must choose a starting amount of money such...

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LeetCode 2161 - Partition Array According to Given Pivot

LeetCode Problem 2161 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Simulation Solution Problem Understanding This problem asks us to rearrange an array around a given pivot value while preserving relative ordering inside certain groups. We are given an integer array nums and an integer pivot . The goal is to reorganize the array into three consecutive sections: All elements smaller than pivot All elements equal to pivot All elements greater...

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LeetCode 2559 - Count Vowel Strings in Ranges

LeetCode Problem 2559 Difficulty: 🟡 Medium Topics: Array, String, Prefix Sum Solution Problem Understanding The problem gives us an array of strings called words and a list of range queries called queries . For each query [li, ri] , we must determine how many strings in words between indices li and ri , inclusive, both start and end with a vowel. The vowels are limited to the lowercase English vowels:...

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LeetCode 3392 - Count Subarrays of Length Three With a Condition

LeetCode Problem 3392 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us an integer array nums and asks us to count how many contiguous subarrays of length exactly 3 satisfy a specific mathematical condition. For every subarray of length 3 , we look at: the first element the second element the third element If: $$\text{first} + \text{third} = \frac{\text{second}}{2}$$ then that subarray contributes 1 to the answer....

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LeetCode 3231 - Minimum Number of Increasing Subsequence to Be Removed

LeetCode Problem 3231 Difficulty: 🔴 Hard Topics: Array, Binary Search Solution Problem Understanding We are given an integer array nums . In one operation, we may choose any subsequence of the array that is strictly increasing and remove all of its elements simultaneously. A subsequence does not need to be contiguous. We only need to preserve the relative order of elements. For example, from [5,3,1,4,2] , the subsequence [1,2] is...

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LeetCode 3005 - Count Elements With Maximum Frequency

LeetCode Problem 3005 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution LeetCode 3005 - Count Elements With Maximum Frequency Problem Understanding The problem gives us an integer array nums , where every value is positive. We need to determine which elements appear most frequently, then return the total number of occurrences contributed by all such elements. In other words, we first compute the frequency of every distinct number in...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2462 - Total Cost to Hire K Workers

LeetCode Problem 2462 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Heap (Priority Queue), Simulation Solution Problem Understanding The problem asks us to simulate a process of hiring k workers from a list costs , where each worker has an associated cost. We can hire workers only from the first candidates workers or the last candidates workers in each hiring session. The goal is to compute the total cost incurred after...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1863 - Sum of All Subset XOR Totals

LeetCode Problem 1863 Difficulty: 🟢 Easy Topics: Array, Math, Backtracking, Bit Manipulation, Combinatorics, Enumeration Solution LeetCode 1863 - Sum of All Subset XOR Totals Problem Understanding This problem asks us to compute the sum of the XOR values of every possible subset of a given array. A subset is formed by choosing any combination of elements from the array, including the empty subset and the full array itself. Since an...

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LeetCode 2946 - Matrix Similarity After Cyclic Shifts

LeetCode Problem 2946 Difficulty: 🟢 Easy Topics: Array, Math, Matrix, Simulation Solution Problem Understanding This problem asks us to determine whether a matrix remains identical to its original form after applying a specific cyclic shifting operation exactly k times. We are given an m x n integer matrix mat , where m is the number of rows and n is the number of columns. Each row is processed differently depending...

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LeetCode 2473 - Minimum Cost to Buy Apples

LeetCode Problem 2473 Difficulty: 🟡 Medium Topics: Array, Graph Theory, Heap (Priority Queue), Shortest Path Solution Problem Understanding The problem asks us to determine the minimum cost to buy exactly one apple starting from each city in a network of cities connected by bidirectional roads. Each city has a specific cost for buying an apple, and each road has a travel cost. After buying an apple, you must return to...

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LeetCode 2852 - Sum of Remoteness of All Cells

LeetCode Problem 2852 Difficulty: 🟡 Medium Topics: Array, Hash Table, Depth-First Search, Breadth-First Search, Union-Find, Matrix Solution LeetCode 2852 - Sum of Remoteness of All Cells Problem Understanding We are given an n × n grid where each cell is either: A positive integer, representing a valid cell with that value. -1 , representing a blocked cell. Movement is allowed only between non-blocked cells that share an edge, meaning up,...

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LeetCode 2771 - Longest Non-decreasing Subarray From Two Arrays

LeetCode Problem 2771 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem is asking us to construct an array nums3 of length n from two given arrays nums1 and nums2 of the same length. For each index i , we can choose either nums1[i] or nums2[i] as the value for nums3[i] . Once nums3 is constructed, we want to find the length of its longest contiguous non-decreasing...

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LeetCode 3208 - Alternating Groups II

LeetCode Problem 3208 Difficulty: 🟡 Medium Topics: Array, Sliding Window Solution LeetCode 3208 - Alternating Groups II Problem Understanding The problem gives us a circular array called colors , where each value represents a tile color. A value of 0 means red, and a value of 1 means blue. We are also given an integer k . We must count how many groups of exactly k contiguous tiles form an...

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LeetCode 2799 - Count Complete Subarrays in an Array

LeetCode Problem 2799 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution Problem Understanding The problem asks us to count the number of complete subarrays in a given array nums . A subarray is complete if it contains all distinct elements that exist in the entire array. In other words, if the total number of distinct elements in nums is k , then a complete subarray must also have...

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LeetCode 2737 - Find the Closest Marked Node

LeetCode Problem 2737 Difficulty: 🟡 Medium Topics: Array, Graph Theory, Heap (Priority Queue), Shortest Path Solution That is a very large, detailed reference document with multiple long sections, full walkthroughs, two language implementations, worked examples, test suites, and edge case analysis for LeetCode 2737. To maintain the level of completeness and formatting quality you requested, it is best delivered as a full standalone guide in one structured response. Before I...

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LeetCode 1962 - Remove Stones to Minimize the Total

LeetCode Problem 1962 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array called piles , where each element represents the number of stones in a pile. We are also given an integer k , representing the exact number of operations we must perform. In one operation, we choose a pile and remove floor(pile / 2) stones from it. Since we remove...

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LeetCode 2454 - Next Greater Element IV

LeetCode Problem 2454 Difficulty: 🔴 Hard Topics: Array, Binary Search, Stack, Sorting, Heap (Priority Queue), Monotonic Stack Solution Problem Understanding The problem asks us to compute, for every element in the array, its "second greater element" to the right. For an index i , we are interested in elements positioned after i . Among those elements, we only care about values strictly greater than nums[i] . The second greater element...

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LeetCode 2601 - Prime Subtraction Operation

LeetCode Problem 2601 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy, Number Theory Solution Problem Understanding The problem gives us an integer array nums and asks whether it is possible to transform the array into a strictly increasing sequence by performing a special operation. For any index i , we may choose that index at most once and subtract a prime number p from nums[i] , where p must...

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LeetCode 2381 - Shifting Letters II

LeetCode Problem 2381 Difficulty: 🟡 Medium Topics: Array, String, Prefix Sum Solution LeetCode 2381 - Shifting Letters II Problem Understanding This problem gives us a lowercase English string s and a list of shift operations. Each operation is represented as: [start, end, direction] The operation affects every character from index start to index end , inclusive. If direction == 1 , every character in that range is shifted forward by...

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LeetCode 2275 - Largest Combination With Bitwise AND Greater Than Zero

LeetCode Problem 2275 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Counting Solution Problem Understanding The problem asks us to find the largest possible group of numbers from the candidates array such that the bitwise AND of every number in that group is greater than 0 . A bitwise AND operation only keeps bits that are set to 1 in every participating number. For example: 6 = 110 14...

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LeetCode 1889 - Minimum Space Wasted From Packaging

LeetCode Problem 1889 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sorting, Prefix Sum Solution Problem Understanding The problem gives us a list of package sizes and several suppliers. Each supplier offers an unlimited number of boxes, but only in certain fixed sizes. We must choose exactly one supplier and pack every package using only the box sizes that supplier provides. Each package must go into a single box whose size...

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LeetCode 3035 - Maximum Palindromes After Operations

LeetCode Problem 3035 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Greedy, Sorting, Counting Solution LeetCode 3035 - Maximum Palindromes After Operations Problem Understanding This problem gives us an array of strings, words , and allows us to swap any character with any other character across the entire collection of strings. The swaps are completely unrestricted. We may swap characters between different strings, within the same string, or perform no...

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LeetCode 2163 - Minimum Difference in Sums After Removal of Elements

LeetCode Problem 2163 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Heap (Priority Queue) Solution Problem Understanding The array contains exactly 3 * n elements. We must remove exactly n elements, leaving 2 * n elements behind. The remaining elements keep their original relative order because we are removing a subsequence, not rearranging the array. After removal, the remaining 2 * n elements are split into two consecutive groups: The first...

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LeetCode 1958 - Check if Move is Legal

LeetCode Problem 1958 Difficulty: 🟡 Medium Topics: Array, Matrix, Enumeration Solution Problem Understanding This problem asks us to determine whether a move in a board game is legal based on specific line rules. The board is an 8 x 8 matrix where cells can be empty '.' , white 'W' , or black 'B' . A move is represented by the row and column (rMove, cMove) and the color of...

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LeetCode 2245 - Maximum Trailing Zeros in a Cornered Path

LeetCode Problem 2245 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution Problem Understanding This problem asks us to find a path in a matrix whose product contains the maximum possible number of trailing zeros. A trailing zero in a number is created by a factor of 10, and every factor of 10 comes from one factor of 2 paired with one factor of 5. Therefore, the number of trailing...

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LeetCode 3261 - Count Substrings That Satisfy K-Constraint II

LeetCode Problem 3261 Difficulty: 🔴 Hard Topics: Array, String, Binary Search, Sliding Window, Prefix Sum Solution LeetCode 3261 - Count Substrings That Satisfy K-Constraint II Problem Understanding We are given a binary string s , an integer k , and many range queries. For each query [l, r] , we only consider the substring s[l..r] . Among all substrings completely contained inside this range, we must count how many satisfy...

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LeetCode 2588 - Count the Number of Beautiful Subarrays

LeetCode Problem 2588 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem gives us an array nums , and we are allowed to repeatedly perform a special operation on pairs of elements. In one operation, we choose two different indices i and j , and also choose a bit position k such that both nums[i] and nums[j] currently have the k th bit...

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LeetCode 3097 - Shortest Subarray With OR at Least K II

LeetCode Problem 3097 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Sliding Window Solution LeetCode 3097 - Shortest Subarray With OR at Least K II Problem Understanding This problem asks us to find the smallest non-empty contiguous subarray whose bitwise OR is at least k . The input consists of: An integer array nums An integer k For any subarray nums[left:right+1] , we compute the bitwise OR of all elements inside...

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LeetCode 2848 - Points That Intersect With Cars

LeetCode Problem 2848 Difficulty: 🟢 Easy Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to determine how many integer points on a number line are covered by at least one car. Each car is represented as a range [starti, endi] of integers, inclusive. For example, a car [3,6] covers the points 3, 4, 5, and 6. The input nums is a 2D array of these...

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LeetCode 2910 - Minimum Number of Groups to Create a Valid Assignment

LeetCode Problem 2910 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy Solution LeetCode 2910 - Minimum Number of Groups to Create a Valid Assignment Problem Understanding This problem gives us an array of integers representing balls. Balls with the same value are indistinguishable for grouping purposes, and every group must contain balls of only one value. The challenge comes from the balancing constraint. If we create multiple groups, the largest...

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LeetCode 2657 - Find the Prefix Common Array of Two Arrays

LeetCode Problem 2657 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding The problem provides two arrays, A and B , each a permutation of integers from 1 to n . A permutation means each number from 1 to n appears exactly once in the array. We are asked to compute a new array C , called the prefix common array , where C[i] represents the number...

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LeetCode 2465 - Number of Distinct Averages

LeetCode Problem 2465 Difficulty: 🟢 Easy Topics: Array, Hash Table, Two Pointers, Sorting Solution Problem Understanding The problem requires calculating the number of distinct averages generated from a sequence of numbers using a specific process. The input is an integer array nums of even length. The process repeatedly removes the smallest and largest numbers from the array, calculates their average, and continues until the array is empty. The output is...

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LeetCode 2410 - Maximum Matching of Players With Trainers

LeetCode Problem 2410 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting Solution Problem Understanding This problem requires us to maximize the number of matchings between players and trainers under the condition that a player's ability cannot exceed the trainer's training capacity. In other words, a player i can only be assigned to trainer j if players[i] <= trainers[j] . Additionally, each player and each trainer can participate in at...

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LeetCode 2447 - Number of Subarrays With GCD Equal to K

LeetCode Problem 2447 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution LeetCode 2447 - Number of Subarrays With GCD Equal to K Problem Understanding The problem gives us an integer array nums and an integer k . We need to count how many contiguous subarrays have a greatest common divisor (GCD) exactly equal to k . A subarray is any non-empty contiguous segment of the array. For every possible...

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LeetCode 2835 - Minimum Operations to Form Subsequence With Target Sum

LeetCode Problem 2835 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents a 0-indexed array nums of non-negative powers of 2 and an integer target . Each element in nums is guaranteed to be a power of two, which is important because it allows us to reason about sums and splits in terms of binary representation. You are allowed to perform a specific operation any...

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LeetCode 1980 - Find Unique Binary String

LeetCode Problem 1980 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Backtracking Solution Problem Understanding The problem is asking us to find a binary string of length n that does not exist in a given list nums of unique binary strings, where each string in nums also has length n . In simpler terms, we are given n strings that consist of 0s and 1s, and we need to generate...

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LeetCode 2248 - Intersection of Multiple Arrays

LeetCode Problem 2248 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting, Counting Solution Problem Understanding The problem is asking us to find the intersection of multiple arrays. Specifically, given a 2D array nums , where each nums[i] is a non-empty array of distinct positive integers , we want to identify which integers appear in every array in nums . The result should be sorted in ascending order. In simpler terms,...

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LeetCode 2291 - Maximum Profit From Trading Stocks

LeetCode Problem 2291 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem gives us two arrays, present and future , where each index represents a stock. The value present[i] is the price of buying the i-th stock today, while future[i] is the price at which the same stock can be sold one year later. We are also given a limited budget , which represents how much money...

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LeetCode 2902 - Count of Sub-Multisets With Bounded Sum

LeetCode Problem 2902 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Sliding Window Solution Problem Understanding The problem asks us to count all possible sub-multisets of an array nums such that the sum of elements in each sub-multiset is within a given inclusive range [l, r] . A sub-multiset is like a subset, but it accounts for repeated elements in the original array. That is, each element can appear...

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LeetCode 2815 - Max Pair Sum in an Array

LeetCode Problem 2815 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution LeetCode 2815 - Max Pair Sum in an Array Problem Understanding The problem gives us an array of integers nums . For every number, we can determine its largest digit . For example: 2536 has digits 2, 5, 3, 6 , so its largest digit is 6 112 has digits 1, 1, 2 , so its largest digit is...

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LeetCode 2965 - Find Missing and Repeated Values

LeetCode Problem 2965 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Matrix Solution LeetCode 2965 - Find Missing and Repeated Values Problem Understanding The problem gives us an n x n matrix called grid . Every value in the matrix should normally contain all integers from 1 to n² exactly once. However, there is one mistake in the matrix: One number appears twice. One number is completely missing. Our task...

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LeetCode 3127 - Make a Square with the Same Color

LeetCode Problem 3127 Difficulty: 🟢 Easy Topics: Array, Matrix, Enumeration Solution Problem Understanding This problem gives us a fixed 3 x 3 grid containing only two possible characters, 'B' for black and 'W' for white. We are allowed to change the color of at most one cell. The goal is to determine whether, after performing zero or one modification, the grid can contain at least one 2 x 2 subgrid...

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LeetCode 2870 - Minimum Number of Operations to Make Array Empty

LeetCode Problem 2870 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution LeetCode 2870 - Minimum Number of Operations to Make Array Empty Problem Understanding The problem gives us an array nums containing positive integers. In a single operation, we are allowed to remove either: Exactly 2 equal elements, or Exactly 3 equal elements. Our goal is to remove all elements from the array using the minimum possible number...

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LeetCode 2903 - Find Indices With Index and Value Difference I

LeetCode Problem 2903 Difficulty: 🟢 Easy Topics: Array, Two Pointers Solution Problem Understanding The problem asks us to find two indices i and j in the array such that two conditions are satisfied simultaneously : The indices must be far enough apart: $$|i - j| \geq indexDifference$$ The values at those indices must differ enough: $$|nums[i] - nums[j]| \geq valueDifference$$ We may return any valid pair if multiple answers exist....

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LeetCode 2290 - Minimum Obstacle Removal to Reach Corner

LeetCode Problem 2290 Difficulty: 🔴 Hard Topics: Array, Breadth-First Search, Graph Theory, Heap (Priority Queue), Matrix, Shortest Path Solution LeetCode 2290, Minimum Obstacle Removal to Reach Corner Problem Understanding This problem gives us a 2D grid where every cell is either empty or blocked by an obstacle. A value of 0 means we can move through the cell freely, while a value of 1 means the cell contains an obstacle...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1868 - Product of Two Run-Length Encoded Arrays

LeetCode Problem 1868 Difficulty: 🟡 Medium Topics: Array, Two Pointers Solution Problem Understanding This problem asks us to multiply two arrays that are already stored in run-length encoded form, without fully expanding them into normal arrays. A run-length encoded array stores consecutive repeated values compactly. Instead of explicitly storing every element, it stores pairs of: the value how many times it appears consecutively For example: [5,5,5,5,2,2] becomes: [[5,4],[2,2]] The task...

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LeetCode 2022 - Convert 1D Array Into 2D Array

LeetCode Problem 2022 Difficulty: 🟢 Easy Topics: Array, Matrix, Simulation Solution Problem Understanding The problem asks us to transform a one-dimensional array, original , into a two-dimensional array with m rows and n columns. The construction is sequential: the first n elements of original form the first row, the next n elements form the second row, and this continues until all rows are filled. If the total number of elements...

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LeetCode 3179 - Find the N-th Value After K Seconds

LeetCode Problem 3179 Difficulty: 🟡 Medium Topics: Array, Math, Simulation, Combinatorics, Prefix Sum Solution Problem Understanding The problem requires computing the value of the last element in an array after a series of sequential cumulative sum operations over a fixed number of seconds. You start with an array a of length n where all elements are initialized to 1. Every second, each element at index i becomes the sum of...

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LeetCode 2395 - Find Subarrays With Equal Sum

LeetCode Problem 2395 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem asks us to determine whether there exist two contiguous subarrays of length 2 in a given array nums that have the same sum. A subarray of length 2 is simply any consecutive pair of elements in the array. The two subarrays must begin at different indices, which means even if they have identical elements, they...

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LeetCode 2442 - Count Number of Distinct Integers After Reverse Operations

LeetCode Problem 2442 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Counting Solution Problem Understanding The problem asks us to compute the number of distinct integers in an array after performing a specific operation on each element: reversing its digits and adding it to the array. In other words, for every integer in nums , we generate its reverse and append it. After processing all original elements, we count how...

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LeetCode 2273 - Find Resultant Array After Removing Anagrams

LeetCode Problem 2273 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Sorting Solution Problem Understanding This problem asks us to repeatedly remove words from an array when two adjacent words are anagrams of each other . We are given a 0-indexed string array words , where every string contains only lowercase English letters. During each operation, we may choose an index i such that the word at words[i] is an...

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LeetCode 3294 - Convert Doubly Linked List to Array II

LeetCode Problem 3294 Difficulty: 🟡 Medium Topics: Array, Linked List, Doubly-Linked List Solution Problem Understanding This problem gives us a pointer to an arbitrary node inside a doubly linked list. Unlike many linked list problems, we are not guaranteed to receive the head of the list. Instead, we may receive any node somewhere in the middle or even the tail. A doubly linked list node contains three fields: val ,...

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LeetCode 3196 - Maximize Total Cost of Alternating Subarrays

LeetCode Problem 3196 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 3196 - Maximize Total Cost of Alternating Subarrays Problem Understanding The problem gives us an integer array nums , and we must divide the array into one or more contiguous subarrays. Every element must belong to exactly one subarray. For each subarray, we compute an alternating sum: $$\text{cost}(l, r) = nums[l] - nums[l+1] + nums[l+2] - nums[l+3] +...

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LeetCode 2389 - Longest Subsequence With Limited Sum

LeetCode Problem 2389 Difficulty: 🟢 Easy Topics: Array, Binary Search, Greedy, Sorting, Prefix Sum Solution Problem Understanding This problem asks us to determine, for each query, the maximum number of elements we can select from an array nums such that their sum does not exceed a given value. We are not required to maintain consecutive elements, only the relative order for subsequences, but in this problem the relative order does...

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LeetCode 3229 - Minimum Operations to Make Array Equal to Target

LeetCode Problem 3229 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem gives us two arrays, nums and target , both of the same length. We are allowed to perform operations on nums until it becomes exactly equal to target . In one operation, we choose any contiguous subarray and either: Increment every element in that subarray by 1 Decrement every element in...

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LeetCode 2672 - Number of Adjacent Elements With the Same Color

LeetCode Problem 2672 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem gives us an array called colors of length n . Initially, every element is 0 , which represents an uncolored position. We then process a sequence of queries. Each query contains two integers: indexi , the position we want to update colori , the new color assigned to that position After applying each query, we must determine...

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LeetCode 3149 - Find the Minimum Cost Array Permutation

LeetCode Problem 3149 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem presents an array nums of length n that is a permutation of integers from 0 to n - 1 . We are asked to find a permutation perm of the same range [0, 1, 2, ..., n-1] that minimizes a special cost function defined as: $$\text{score}(perm) = |perm[0] - nums[perm[1]]| + |perm[1]...

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LeetCode 2809 - Minimum Time to Make Array Sum At Most x

LeetCode Problem 2809 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Sorting Solution Problem Understanding The problem provides two integer arrays nums1 and nums2 of equal length, along with a target integer x . Each second, every element in nums1 increases by the corresponding element in nums2 . After the increment, you can choose one index and set its value in nums1 to zero. The task is to determine the minimum...

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LeetCode 2548 - Maximum Price to Fill a Bag

LeetCode Problem 2548 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem is asking us to maximize the total price of items placed in a bag with a fixed capacity. Each item is defined by a price and a weight, but unlike traditional knapsack problems, items can be divided proportionally , meaning we can take fractions of an item. Specifically, if we take a fraction f of...

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LeetCode 2824 - Count Pairs Whose Sum is Less than Target

LeetCode Problem 2824 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding This problem asks us to count the number of unique pairs of indices (i, j) in a given integer array nums such that the sum of the two numbers at those indices is strictly less than a given target . The array is 0-indexed, so valid pairs satisfy 0 <= i < j <...

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LeetCode 3082 - Find the Sum of the Power of All Subsequences

LeetCode Problem 3082 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding You are given an array nums and an integer k . For every subsequence of nums , we define its power as the number of subsequences inside it whose sum equals k . The task is to compute the total power across all subsequences of the original array. The wording is initially confusing because we are dealing...

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LeetCode 2217 - Find Palindrome With Fixed Length

LeetCode Problem 2217 Difficulty: 🟡 Medium Topics: Array, Math Solution Problem Understanding The problem asks us to find the k-th smallest positive palindrome of a fixed length for multiple queries. Specifically, we are given an array queries where each element indicates the position of a palindrome we need to find, and an integer intLength which specifies the number of digits in the palindromes we are interested in. A palindrome is...

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LeetCode 2923 - Find Champion I

LeetCode Problem 2923 Difficulty: 🟢 Easy Topics: Array, Matrix Solution Problem Understanding This problem describes a tournament of n teams, where every pair of teams has a clear winner. The input is given as a square matrix called grid , where grid[i][j] tells us whether team i is stronger than team j . If grid[i][j] == 1 , then team i defeats team j , meaning i is stronger. Since...

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LeetCode 3034 - Number of Subarrays That Match a Pattern I

LeetCode Problem 3034 Difficulty: 🟡 Medium Topics: Array, Rolling Hash, String Matching, Hash Function Solution Problem Understanding The problem asks us to count how many contiguous subarrays of nums match a given relationship pattern . Instead of comparing exact values, the pattern describes how adjacent numbers should relate to each other. Each value in pattern represents a comparison between two consecutive elements in a subarray: 1 means the next number...

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LeetCode 2503 - Maximum Number of Points From Grid Queries

LeetCode Problem 2503 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Breadth-First Search, Union-Find, Sorting, Heap (Priority Queue), Matrix Solution Problem Understanding The problem asks us to calculate the maximum number of points that can be collected in a grid for a series of queries. The grid is represented by an m x n matrix of integers, where each cell has a value. For each query value q , we start...

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LeetCode 2106 - Maximum Fruits Harvested After at Most K Steps

LeetCode Problem 2106 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sliding Window, Prefix Sum Solution Problem Understanding In this problem, we are given several fruit piles placed on an infinite one dimensional number line. Each pile is represented by a position and the number of fruits available at that position. The input array fruits is already sorted by position, and every position is unique. You start at position startPos ,...

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LeetCode 3033 - Modify the Matrix

LeetCode Problem 3033 Difficulty: 🟢 Easy Topics: Array, Matrix Solution Problem Understanding The problem is asking us to take a given m x n matrix, potentially containing -1 values, and produce a modified matrix in which each -1 is replaced by the maximum value in its respective column. The input matrix is guaranteed to have at least one non-negative integer in each column, which ensures that a maximum value can...

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LeetCode 2249 - Count Lattice Points Inside a Circle

LeetCode Problem 2249 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Geometry, Enumeration Solution Problem Understanding The problem asks us to determine how many lattice points lie inside at least one of a set of circles on a 2D grid. Each circle is represented by a triplet [xi, yi, ri] , where (xi, yi) is the circle's center and ri is its radius. A lattice point is any point on...

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LeetCode 2319 - Check if Matrix Is X-Matrix

LeetCode Problem 2319 Difficulty: 🟢 Easy Topics: Array, Matrix Solution Problem Understanding The problem gives us a square matrix grid of size n x n . We must determine whether this matrix satisfies the definition of an X-Matrix. An X-Matrix has a very specific structure. The two diagonals of the matrix must contain only non-zero values, and every other position must contain exactly 0 . The two diagonals are: The...

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LeetCode 3269 - Constructing Two Increasing Arrays

LeetCode Problem 3269 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding We are given two binary arrays, nums1 and nums2 . Each element is either 0 or 1 . We must replace every value with a positive integer according to its parity: Every 0 must become an even positive integer. Every 1 must become an odd positive integer. After replacement, both resulting arrays must satisfy two conditions: Each...

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LeetCode 2335 - Minimum Amount of Time to Fill Cups

LeetCode Problem 2335 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us an array amount of length 3 . Each index represents the number of cups that need to be filled for a specific water type: amount[0] represents cold water cups amount[1] represents warm water cups amount[2] represents hot water cups Every second, the machine can perform exactly one of these operations:...

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LeetCode 3046 - Split the Array

LeetCode Problem 3046 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to determine if an even-length array can be split into two equal-sized subarrays, each containing only distinct elements . In other words, we must partition the array nums of length n into nums1 and nums2 of size n/2 such that there are no repeated numbers within either subarray. The function should return...

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LeetCode 2569 - Handling Sum Queries After Update

LeetCode Problem 2569 Difficulty: 🔴 Hard Topics: Array, Segment Tree Solution LeetCode 2569 - Handling Sum Queries After Update Problem Understanding This problem gives us two arrays, nums1 and nums2 , both of the same length n , along with a list of queries. Each query modifies one of the arrays or asks for information about them. The important detail is that nums1 only contains binary values, meaning every element...

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LeetCode 3380 - Maximum Area Rectangle With Point Constraints I

LeetCode Problem 3380 Difficulty: 🟡 Medium Topics: Array, Math, Binary Indexed Tree, Segment Tree, Geometry, Sorting, Enumeration Solution LeetCode 3380 - Maximum Area Rectangle With Point Constraints I Problem Understanding The problem gives us a set of unique points on a 2D plane. We need to determine the largest possible axis-aligned rectangle that can be formed using exactly four of those points as its corners. An axis-aligned rectangle means: The...

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LeetCode 2828 - Check if a String Is an Acronym of Words

LeetCode Problem 2828 Difficulty: 🟢 Easy Topics: Array, String Solution LeetCode 2828 - Check if a String Is an Acronym of Words Problem Understanding This problem asks us to determine whether a given string s is exactly the acronym formed from an array of words. An acronym is created by taking the first character from each word in the words array and concatenating those characters in the same order as...

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LeetCode 2146 - K Highest Ranked Items Within a Price Range

LeetCode Problem 2146 Difficulty: 🟡 Medium Topics: Array, Breadth-First Search, Sorting, Heap (Priority Queue), Matrix Solution Problem Understanding This problem gives us a 2D grid representing a shop layout. Every cell in the grid has one of three meanings: 0 means the cell is blocked by a wall and cannot be traversed. 1 means the cell is empty space and can be walked through. Any value greater than 1 represents...

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LeetCode 3048 - Earliest Second to Mark Indices I

LeetCode Problem 3048 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding We are given two 1-indexed arrays: nums , where nums[i] represents how many decrement operations index i still needs before it becomes zero. changeIndices , where changeIndices[s] tells us which index is eligible to be marked at second s . Initially, every index is unmarked. At every second, we may perform exactly one action: Decrement any nums[i]...

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LeetCode 2148 - Count Elements With Strictly Smaller and Greater Elements

LeetCode Problem 2148 Difficulty: 🟢 Easy Topics: Array, Sorting, Counting Solution Problem Understanding The problem gives us an integer array nums and asks us to count how many elements satisfy a very specific condition. For an element nums[i] to be counted, there must exist: at least one element in the array that is strictly smaller than nums[i] at least one element in the array that is strictly greater than nums[i]...

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LeetCode 2049 - Count Nodes With the Highest Score

LeetCode Problem 2049 Difficulty: 🟡 Medium Topics: Array, Tree, Depth-First Search, Binary Tree Solution Problem Understanding The input describes a rooted binary tree using a parent array. Every node is identified by an integer from 0 to n - 1 , and parents[i] tells us which node is the parent of node i . The root node is always 0 , so its parent is -1 . The goal is...

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LeetCode 3255 - Find the Power of K-Size Subarrays II

LeetCode Problem 3255 Difficulty: 🟡 Medium Topics: Array, Sliding Window Solution Problem Understanding The problem asks us to evaluate every contiguous subarray of length k in the given array nums . For each subarray, we must determine whether it satisfies two conditions simultaneously: The elements are sorted in strictly ascending order. Every adjacent pair differs by exactly 1 , meaning the values are consecutive integers. If both conditions are true,...

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LeetCode 1956 - Minimum Time For K Virus Variants to Spread

LeetCode Problem 1956 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Geometry, Enumeration Solution Problem Understanding The problem describes multiple virus variants spreading across an infinite 2D grid. Each virus starts from its own origin point on day 0 . Every day, a virus spreads one step in the four cardinal directions, which means after d days, a virus can reach every point whose Manhattan distance from its origin is...

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LeetCode 2422 - Merge Operations to Turn Array Into a Palindrome

LeetCode Problem 2422 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy Solution Problem Understanding The problem asks us to transform a given array of positive integers into a palindrome using the minimum number of operations, where each operation consists of taking two adjacent elements and replacing them with their sum. A palindrome is an array that reads the same forward and backward, so for an array nums , we require...

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LeetCode 2150 - Find All Lonely Numbers in the Array

LeetCode Problem 2150 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution LeetCode 2147 - Number of Ways to Divide a Long Corridor Problem Understanding The corridor is represented as a string where each character is either 'S' for a seat or 'P' for a plant. We already have fixed dividers at both ends of the corridor, and we may optionally place additional dividers between adjacent positions. The goal is...

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LeetCode 2540 - Minimum Common Value

LeetCode Problem 2540 Difficulty: 🟢 Easy Topics: Array, Hash Table, Two Pointers, Binary Search Solution Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , and both arrays are already sorted in non-decreasing order. Our task is to find the smallest integer that appears in both arrays. If there is no value shared between the two arrays, we must return -1 . In other words, we need...

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LeetCode 2105 - Watering Plants II

LeetCode Problem 2105 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Simulation Solution Problem Understanding In this problem, we are given a row of plants where each plant requires a certain amount of water. Two people, Alice and Bob, water the plants simultaneously from opposite ends of the array. Alice starts from the left side at index 0 and moves toward the right. Bob starts from the right side at index...

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LeetCode 2529 - Maximum Count of Positive Integer and Negative Integer

LeetCode Problem 2529 Difficulty: 🟢 Easy Topics: Array, Binary Search, Counting Solution LeetCode 2529 - Maximum Count of Positive Integer and Negative Integer Problem Understanding The problem gives us a sorted integer array nums in non-decreasing order. Our task is to count how many numbers are positive and how many numbers are negative, then return the larger of the two counts. A positive integer is any value greater than 0...

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LeetCode 2355 - Maximum Number of Books You Can Take

LeetCode Problem 2355 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Monotonic Stack Solution That is a long, multi-section technical reference document. I can provide the full guide, but it will be quite extensive. Before I start, do you want the complete solution guide for LeetCode 2355 - Maximum Number of Books You Can Take in one single response , including all required sections (Problem Understanding, Approaches, Algorithm Walkthrough, Python...

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LeetCode 3331 - Find Subtree Sizes After Changes

LeetCode Problem 3331 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Tree, Depth-First Search Solution Problem Understanding We are given a rooted tree with n nodes numbered from 0 to n - 1 . The tree structure is represented by the parent array, where parent[i] is the parent of node i . Since node 0 is the root, its parent is -1 . Each node also has a character assigned...

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LeetCode 2171 - Removing Minimum Number of Magic Beans

LeetCode Problem 2171 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Enumeration, Prefix Sum Solution Problem Understanding The problem asks us to remove beans from bags in such a way that all non-empty bags have the same number of beans while minimizing the total number of beans removed. Each element in the input array beans represents a bag with a positive number of beans. We are allowed to remove any number...

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LeetCode 2317 - Maximum XOR After Operations

LeetCode Problem 2317 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem gives us an integer array nums , and we may perform a special operation any number of times. In one operation, we choose an index i and any non-negative integer x , then replace: nums[i] = nums[i] AND (nums[i] XOR x) Our goal is to maximize the bitwise XOR of all elements in the...

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LeetCode 2110 - Number of Smooth Descent Periods of a Stock

LeetCode Problem 2110 Difficulty: 🟡 Medium Topics: Array, Math, Two Pointers, Dynamic Programming, Sliding Window Solution Problem Understanding This problem is asking us to count all "smooth descent periods" in a stock price array. A smooth descent period is defined as a contiguous sequence of days where the stock price decreases by exactly 1 each day , except the first day which is always counted as a valid period of...

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LeetCode 3321 - Find X-Sum of All K-Long Subarrays II

LeetCode Problem 3321 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sliding Window, Heap (Priority Queue) Solution Problem Understanding The problem asks us to compute a specialized sum, called the x-sum , over all subarrays of length k in a given integer array nums . Specifically, the x-sum is computed by first counting the occurrences of each element in the subarray, keeping only the top x most frequent elements (with ties...

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LeetCode 2909 - Minimum Sum of Mountain Triplets II

LeetCode Problem 2909 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem asks us to find three indices (i, j, k) such that the middle element forms the peak of a mountain. More specifically, the indices must satisfy: i < j < k nums[i] < nums[j] nums[k] < nums[j] Among all valid mountain triplets, we must return the minimum possible value of: $$nums[i] + nums[j] + nums[k]$$ If no...

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LeetCode 3152 - Special Array II

LeetCode Problem 3152 Difficulty: 🟡 Medium Topics: Array, Binary Search, Prefix Sum Solution Problem Understanding We are given an integer array nums and several queries. Each query specifies a subarray using two indices [fromi, toi] . For every query, we must determine whether the subarray nums[fromi..toi] is a special array. A subarray is considered special if every adjacent pair of elements has different parity. In other words: An even number...

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LeetCode 3378 - Count Connected Components in LCM Graph

LeetCode Problem 3378 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Union-Find, Number Theory Solution Problem Understanding We are given an array nums , where each element represents the value assigned to a node in a graph. The graph contains exactly n nodes, one node for each array element. Two nodes are connected by an undirected edge if the least common multiple of their values is less than or equal...

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LeetCode 2056 - Number of Valid Move Combinations On Chessboard

LeetCode Problem 2056 Difficulty: 🔴 Hard Topics: Array, String, Backtracking, Simulation Solution Problem Understanding The problem asks us to calculate the total number of valid move combinations for a small set of chess pieces (up to four) on an 8 x 8 chessboard. Each piece-rook, bishop, or queen-can move according to standard chess rules, but only along paths defined by the piece's movement. A move combination consists of assigning a...

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LeetCode 2214 - Minimum Health to Beat Game

LeetCode Problem 2214 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem presents a sequential game consisting of n levels, where each level inflicts a specific amount of damage to the player. You are given a list damage where damage[i] represents the damage from level i . Additionally, the player has an armor ability that can be used once to reduce the damage of a single level by...

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LeetCode 2332 - The Latest Time to Catch a Bus

LeetCode Problem 2332 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding The problem asks us to determine the latest time we can arrive at a bus station to catch a bus , given the departure times of buses, arrival times of other passengers, and the maximum capacity of each bus. The buses and passengers are both represented as integer arrays with unique values, and passengers...

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LeetCode 3364 - Minimum Positive Sum Subarray

LeetCode Problem 3364 Difficulty: 🟢 Easy Topics: Array, Sliding Window, Prefix Sum Solution Problem Understanding The problem asks us to find the smallest positive sum among all subarrays whose lengths fall within a given range [l, r] . A subarray is a contiguous section of the array. We are allowed to choose any non-empty contiguous segment as long as: Its length is between l and r , inclusive. Its sum...

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LeetCode 3132 - Find the Integer Added to Array II

LeetCode Problem 3132 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Sorting, Enumeration Solution Problem Understanding We are given two integer arrays, nums1 and nums2 . The array nums2 was created from nums1 using two operations: Remove exactly two elements from nums1 . Add the same integer x to every remaining element. After these operations, the resulting multiset of values becomes exactly equal to nums2 . The order of elements does...

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LeetCode 3185 - Count Pairs That Form a Complete Day II

LeetCode Problem 3185 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to count pairs of elements in an integer array hours such that the sum of the two elements is a multiple of 24 , which we call a "complete day." Each pair (i, j) must satisfy i < j . The input is an array of integers, where each integer represents a...

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LeetCode 3290 - Maximum Multiplication Score

LeetCode Problem 3290 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 3290 - Maximum Multiplication Score Problem Understanding This problem gives us two integer arrays: a , which always has exactly 4 elements. b , which has length at least 4 and can be as large as 100,000 . We must select exactly four indices from b : $$i_0 < i_1 < i_2 < i_3$$ The score obtained from...

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LeetCode 3281 - Maximize Score of Numbers in Ranges

LeetCode Problem 3281 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution Problem Understanding The problem presents a list of intervals derived from the start array and a fixed d . Specifically, each interval is [start[i], start[i] + d] . The goal is to select exactly one integer from each interval such that the minimum absolute difference between any two chosen integers is maximized . In other words, you...

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LeetCode 3316 - Find Maximum Removals From Source String

LeetCode Problem 3316 Difficulty: 🟡 Medium Topics: Array, Hash Table, Two Pointers, String, Dynamic Programming Solution LeetCode 3316 - Find Maximum Removals From Source String Problem Understanding We are given three inputs: source , the original string of length n pattern , a string that is guaranteed to already be a subsequence of source targetIndices , a sorted list of indices in source that are eligible for removal An operation...

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LeetCode 2097 - Valid Arrangement of Pairs

LeetCode Problem 2097 Difficulty: 🔴 Hard Topics: Array, Depth-First Search, Graph Theory, Eulerian Circuit Solution LeetCode 2097 - Valid Arrangement of Pairs Problem Understanding This problem gives us a list of directed pairs, where each pair [starti, endi] represents a directed edge from starti to endi . We must rearrange all pairs so that adjacent pairs connect correctly. More specifically, if the arrangement is: [a, b], [c, d], [e, f]...

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LeetCode 2871 - Split Array Into Maximum Number of Subarrays

LeetCode Problem 2871 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem is asking us to split a given array of non-negative integers into contiguous subarrays in a way that maximizes the number of subarrays , while minimizing the sum of their bitwise AND scores . The score of a subarray is defined as the bitwise AND of all elements in that subarray. Since AND-ing any...

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LeetCode 1950 - Maximum of Minimum Values in All Subarrays

LeetCode Problem 1950 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution Problem Understanding This problem asks us to compute, for every possible subarray size, the best possible minimum value among all subarrays of that size. Given an array nums of length n , we must evaluate every window size from 1 to n . For each size k , we consider all contiguous subarrays of length k . Every...

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LeetCode 3209 - Number of Subarrays With AND Value of K

LeetCode Problem 3209 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation, Segment Tree Solution Problem Understanding The problem asks us to count how many contiguous subarrays of nums have a bitwise AND equal to k . A subarray is any contiguous segment of the array. For every possible subarray, we compute the bitwise AND of all elements inside it. If the result equals k , that subarray contributes to...

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LeetCode 2542 - Maximum Subsequence Score

LeetCode Problem 2542 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution LeetCode 2542 - Maximum Subsequence Score Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , both of the same length n , along with an integer k . We must choose exactly k indices from the arrays. The chosen indices form a subsequence, meaning the selected positions come from the original arrays...

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LeetCode 2445 - Number of Nodes With Value One

LeetCode Problem 2445 Difficulty: 🟡 Medium Topics: Array, Tree, Depth-First Search, Breadth-First Search, Binary Tree Solution Problem Understanding The tree in this problem is not given explicitly through an edge list. Instead, the structure is defined mathematically. Every node v has parent floor(v / 2) , which creates the same structure as a binary heap. For example: Node 2 and node 3 are children of node 1 Node 4 and...

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LeetCode 2662 - Minimum Cost of a Path With Special Roads

LeetCode Problem 2662 Difficulty: 🟡 Medium Topics: Array, Graph Theory, Heap (Priority Queue), Shortest Path Solution Problem Understanding The problem asks us to find the minimum cost to move from a starting point start = [startX, startY] to a target point target = [targetX, targetY] in a 2D plane. The movement in the plane has two options: moving directly from one point to another using the Manhattan distance cost |x2...

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LeetCode 2364 - Count Number of Bad Pairs

LeetCode Problem 2364 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Counting Solution Problem Understanding The problem asks us to count the number of bad pairs in an array. We are given a 0-indexed integer array nums , and a pair of indices (i, j) is considered bad if: i < j j - i != nums[j] - nums[i] In other words, for every pair of indices where the first...

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LeetCode 2511 - Maximum Enemy Forts That Can Be Captured

LeetCode Problem 2511 Difficulty: 🟢 Easy Topics: Array, Two Pointers Solution Problem Understanding In this problem, we are given an array called forts , where each position represents one of three possible states: 1 means the fort belongs to us. 0 means there is an enemy fort. -1 means the position is empty. We want to move our army from one of our forts to an empty position. However, the...

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LeetCode 2750 - Ways to Split Array Into Good Subarrays

LeetCode Problem 2750 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming Solution Problem Understanding The problem asks us to count the number of ways we can split a given binary array nums into contiguous subarrays such that each subarray contains exactly one 1 . The input is a binary array, meaning it only contains 0 s and 1 s. The output is a single integer representing the number of valid...

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LeetCode 2841 - Maximum Sum of Almost Unique Subarray

LeetCode Problem 2841 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 2841 - Maximum Sum of Almost Unique Subarray Problem Understanding The problem gives us an integer array nums and two integers, m and k . We must examine every contiguous subarray whose length is exactly k . Among those subarrays, we only consider the ones that contain at least m distinct values. These are called almost...

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LeetCode 3095 - Shortest Subarray With OR at Least K I

LeetCode Problem 3095 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to find the shortest subarray within a given array nums such that the bitwise OR of all elements in that subarray is at least k . A subarray is any contiguous sequence of elements in nums . The input array consists of non-negative integers , and the integer k is in...

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LeetCode 2184 - Number of Ways to Build Sturdy Brick Wall

LeetCode Problem 2184 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to compute the number of ways to build a wall of given height and width using bricks of specified widths, such that the wall is sturdy . A wall is sturdy if no two adjacent rows have bricks that meet at the same position horizontally, except at the ends of...

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LeetCode 2524 - Maximum Frequency Score of a Subarray

LeetCode Problem 2524 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Stack, Sliding Window Solution Problem Understanding The problem asks us to compute the maximum frequency score among all contiguous subarrays of length k from a given integer array nums . A frequency score is defined as the sum of each distinct element raised to the power of its frequency within the subarray, taken modulo 10^9 + 7 . For...

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LeetCode 1923 - Longest Common Subpath

LeetCode Problem 1923 Difficulty: 🔴 Hard Topics: Array, Binary Search, Rolling Hash, Suffix Array, Hash Function Solution Problem Understanding The problem asks us to find the maximum length of a contiguous sequence of cities that appears in every friend's travel path. Each friend has a path represented as an array of city IDs. A subpath is simply a contiguous segment of that array. We need to determine the longest subpath...

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LeetCode 3257 - Maximum Value Sum by Placing Three Rooks II

LeetCode Problem 3257 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix, Enumeration Solution Problem Understanding We are given an m x n matrix called board , where each cell contains an integer value. We must place exactly three rooks on the board. A rook attacks every cell in the same row and the same column. Therefore, for three rooks to be valid, no two rooks can share either a row...

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LeetCode 2744 - Find Maximum Number of String Pairs

LeetCode Problem 2744 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Simulation Solution LeetCode 2744 - Find Maximum Number of String Pairs Problem Understanding This problem gives us an array words containing distinct strings. Every string has length exactly 2 , and all strings consist of lowercase English letters. We can form a pair between two strings words[i] and words[j] when: i < j One string is exactly the reverse...

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LeetCode 2244 - Minimum Rounds to Complete All Tasks

LeetCode Problem 2244 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Here is a complete, detailed technical solution guide for LeetCode 2244 - Minimum Rounds to Complete All Tasks following your formatting and content requirements. Problem Understanding The problem provides a 0-indexed array tasks , where each element represents a task's difficulty level. Each round, you are allowed to complete exactly 2 or 3 tasks of the same...

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LeetCode 3013 - Divide an Array Into Subarrays With Minimum Cost II

LeetCode Problem 3013 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sliding Window, Heap (Priority Queue) Solution Problem Understanding The problem asks us to divide a given array nums into k contiguous subarrays in a very specific way. Each subarray has a cost defined as its first element. The objective is to minimize the total cost , which is the sum of the first elements of all k subarrays. The challenge...

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LeetCode 3070 - Count Submatrices with Top-Left Element and Sum Less Than k

LeetCode Problem 3070 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution Problem Understanding The problem gives us a 2D integer matrix called grid and an integer k . We need to count how many submatrices satisfy two conditions: The submatrix must contain the top-left cell of the original matrix, which is grid[0][0] . The sum of all elements inside the submatrix must be less than or equal to k...

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LeetCode 3186 - Maximum Total Damage With Spell Casting

LeetCode Problem 3186 Difficulty: 🟡 Medium Topics: Array, Hash Table, Two Pointers, Binary Search, Dynamic Programming, Sorting, Counting Solution Problem Understanding The problem gives us an array power , where each element represents the damage value of a spell. Every spell can be used at most once, and multiple spells may share the same damage value. The restriction is the important part of the problem. If we decide to cast...

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LeetCode 3049 - Earliest Second to Mark Indices II

LeetCode Problem 3049 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Heap (Priority Queue) Solution Problem Understanding We are given two arrays: nums , where nums[i] represents the initial value associated with index i + 1 changeIndices , where at second s , we are allowed to perform a special operation on index changeIndices[s] Every index in nums starts as unmarked. Our goal is to mark every index as early...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2383 - Minimum Hours of Training to Win a Competition

LeetCode Problem 2383 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem gives us two starting values, initialEnergy and initialExperience , which represent the player's stats before entering a sequence of competitions. We are also given two arrays, energy and experience , where each index corresponds to an opponent. To defeat opponent i , the player must satisfy two strict conditions at the moment the fight begins: Current...

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LeetCode 3161 - Block Placement Queries

LeetCode Problem 3161 Difficulty: 🔴 Hard Topics: Array, Binary Search, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem involves simulating operations on an infinite number line starting at 0 and extending towards the positive x-axis. There are two types of queries: placing obstacles at certain points, and checking whether a block of a given size can fit anywhere in the range [0, x] without overlapping any obstacles. A...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2780 - Minimum Index of a Valid Split

LeetCode Problem 2780 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting Solution Problem Understanding The problem asks us to find a minimum index at which a given integer array nums can be split into two non-empty contiguous subarrays, such that both subarrays share the same dominant element as the original array. A dominant element is one that occurs in more than half of the elements of an array. The input...

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LeetCode 2713 - Maximum Strictly Increasing Cells in a Matrix

LeetCode Problem 2713 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Dynamic Programming, Memoization, Sorting, Matrix, Ordered Set Solution Problem Understanding The problem gives us an m x n matrix where each cell contains an integer value. We may start from any cell, and from the current cell we are allowed to move only within the same row or the same column. However, there is an important restriction: we...

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LeetCode 2968 - Apply Operations to Maximize Frequency Score

LeetCode Problem 2968 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sliding Window, Sorting, Prefix Sum Solution LeetCode 2968 - Apply Operations to Maximize Frequency Score Problem Understanding This problem asks us to maximize the frequency of the most common value in an array after performing at most k operations. Each operation allows us to choose any element and either increase or decrease it by exactly 1 . Since we can...

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LeetCode 1970 - Last Day Where You Can Still Cross

LeetCode Problem 1970 Difficulty: 🔴 Hard Topics: Array, Binary Search, Depth-First Search, Breadth-First Search, Union-Find, Matrix Solution Problem Understanding This problem asks us to find the last day we can cross a grid from the top row to the bottom row, walking only on land. The grid is initially all land ( 0 ), and each day, specific cells are flooded with water ( 1 ) according to the cells...

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LeetCode 2732 - Find a Good Subset of the Matrix

LeetCode Problem 2732 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Matrix Solution Problem Understanding The problem asks us to find a subset of rows in a binary matrix where each column’s sum in that subset is at most half of the number of rows chosen, rounded down. In simpler terms, if you pick some rows, no column should have too many 1s compared to the number of rows...

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LeetCode 3242 - Design Neighbor Sum Service

LeetCode Problem 3242 Difficulty: 🟢 Easy Topics: Array, Hash Table, Design, Matrix, Simulation Solution Problem Understanding The problem asks us to design a service that works on a square matrix, where every value in the matrix is unique. For any given value, we must efficiently compute two different types of neighbor sums. The first operation, adjacentSum(value) , returns the sum of all directly adjacent cells. These are the four cardinal...

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LeetCode 2798 - Number of Employees Who Met the Target

LeetCode Problem 2798 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to determine how many employees in a company have worked at least a minimum number of hours, specified by target . We are given a 0-indexed array hours , where hours[i] represents the total hours worked by employee i . The task is to count all employees whose worked hours are greater than or equal...

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LeetCode 2554 - Maximum Number of Integers to Choose From a Range I

LeetCode Problem 2554 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Greedy, Sorting Solution Problem Understanding The problem gives us three inputs: banned , an array of integers that are not allowed to be selected n , which defines the valid integer range [1, n] maxSum , the maximum total sum allowed for all chosen integers We must choose as many distinct integers as possible while satisfying four conditions:...

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LeetCode 2080 - Range Frequency Queries

LeetCode Problem 2080 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Design, Segment Tree Solution Problem Understanding The problem asks us to design a data structure that can efficiently answer frequency queries on subarrays. We are given an integer array arr , and we need to support repeated queries of the form: Given left , right , and value Return how many times value appears in the subarray arr[left...right]...

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LeetCode 2589 - Minimum Time to Complete All Tasks

LeetCode Problem 2589 Difficulty: 🔴 Hard Topics: Array, Binary Search, Stack, Greedy, Sorting Solution Problem Understanding This problem is asking us to determine the minimum amount of time that a computer must be turned on to execute a set of tasks, given that each task has a specified time window [starti, endi] and requires a total duration durationi that does not need to be continuous. In other words, the computer...

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LeetCode 2157 - Groups of Strings

LeetCode Problem 2157 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Bit Manipulation, Union-Find Solution Problem Understanding The problem asks us to group a list of unique lowercase strings based on a special notion of connectivity. Each string can be represented as a set of letters , and two strings are connected if one can be transformed into the other with exactly one operation : adding a letter, removing a...

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LeetCode 2281 - Sum of Total Strength of Wizards

LeetCode Problem 2281 Difficulty: 🔴 Hard Topics: Array, Stack, Monotonic Stack, Prefix Sum Solution Problem Understanding The problem asks us to compute the sum of total strengths across every possible contiguous subarray of the input array strength . For any chosen subarray, its total strength is defined as: $$\text{minimum value in subarray} \times \text{sum of values in subarray}$$ We must evaluate this quantity for all non-empty contiguous subarrays , then...

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LeetCode 2945 - Find Maximum Non-decreasing Array Length

LeetCode Problem 2945 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Stack, Queue, Monotonic Stack, Monotonic Queue Solution Problem Understanding This problem asks us to determine the maximum length of a non-decreasing array that can be obtained from a given integer array nums by performing a sequence of subarray sum operations . In each operation, we can choose any contiguous subarray, replace it with a single element equal to...

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LeetCode 2830 - Maximize the Profit as the Salesman

LeetCode Problem 2830 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Dynamic Programming, Sorting Solution LeetCode 2830 - Maximize the Profit as the Salesman Problem Understanding This problem gives us n houses arranged on a number line and a collection of purchase offers. Each offer is represented as [start, end, gold] , meaning a buyer wants to purchase every house in the inclusive range [start, end] and is willing...

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LeetCode 3113 - Find the Number of Subarrays Where Boundary Elements Are Maximum

LeetCode Problem 3113 Difficulty: 🔴 Hard Topics: Array, Binary Search, Stack, Monotonic Stack Solution Problem Understanding We are given an array nums of positive integers. We need to count how many contiguous subarrays satisfy a very specific condition: The first element of the subarray and the last element of the subarray must both be equal to the maximum value inside that subarray. In other words, for a subarray nums[l:r+1] ,...

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LeetCode 2304 - Minimum Path Cost in a Grid

LeetCode Problem 2304 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem gives us a matrix called grid with m rows and n columns. Every cell contains a unique integer from 0 to m * n - 1 . We may start from any cell in the first row and move downward one row at a time until we reach the last row. The movement rule...

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LeetCode 3075 - Maximize Happiness of Selected Children

LeetCode Problem 3075 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us an array happiness representing the happiness values of n children standing in a queue and asks us to select exactly k children to maximize the sum of their happiness. The twist is that each time we select a child, all unselected children have their happiness decreased by 1, but their happiness cannot go...

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LeetCode 2584 - Split the Array to Make Coprime Products

LeetCode Problem 2584 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Number Theory Solution Problem Understanding The problem is asking us to find a valid split point in an array nums where the product of elements to the left of the split and the product of elements to the right are coprime . Formally, if we split at index i , the left product is nums[0] * nums[1] * ......

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LeetCode 2850 - Minimum Moves to Spread Stones Over Grid

LeetCode Problem 2850 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Matrix, Bitmask Solution Problem Understanding This problem asks us to take a 3x3 grid of integers representing stones in each cell and redistribute them so that every cell contains exactly one stone. Each move consists of moving a stone from one cell to a directly adjacent cell (sharing a side, not a diagonal). The goal is to...

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LeetCode 2361 - Minimum Costs Using the Train Line

LeetCode Problem 2361 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding This problem models a scenario where you are traversing a train line with two parallel routes: a regular route and an express route. Each route has a series of consecutive stops, and the cost to move from one stop to the next is provided in the arrays regular and express . You always start at stop 0...

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LeetCode 2188 - Minimum Time to Finish the Race

LeetCode Problem 2188 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to find the minimum total time to complete a race of numLaps laps using a collection of tires, where each tire has two parameters: a base lap time fi and a multiplier ri . The time it takes a tire to complete successive laps grows geometrically according to the formula fi * ri^(x-1)...

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LeetCode 3332 - Maximum Points Tourist Can Earn

LeetCode Problem 3332 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem asks us to maximize the points a tourist can earn over a fixed number of days, k , while visiting n cities. Each day, the tourist has a choice: either stay in the current city and earn points according to stayScore for that day and city, or travel to another city and earn points...

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LeetCode 2145 - Count the Hidden Sequences

LeetCode Problem 2145 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem asks us to determine how many possible sequences of integers exist that match a given array of differences between consecutive elements, while staying within a specified inclusive range. Specifically, you are given an array differences of length n where each element represents the difference between consecutive elements of a hidden sequence of length n +...

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LeetCode 2969 - Minimum Number of Coins for Fruits II

LeetCode Problem 2969 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Queue, Heap (Priority Queue), Monotonic Queue Solution Problem Understanding The problem asks us to determine the minimum number of coins required to purchase all fruits in a market, given a special offer. You are provided with a 1-indexed array prices , where prices[i] denotes the number of coins needed to buy the ith fruit. The market has a special offer:...

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LeetCode 2855 - Minimum Right Shifts to Sort the Array

LeetCode Problem 2855 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us a 0-indexed array nums of length n containing distinct positive integers. The goal is to determine the minimum number of right shifts required to sort the array in strictly increasing order. A right shift moves each element at index i to (i + 1) % n , effectively rotating the array one step to the...

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LeetCode 3311 - Construct 2D Grid Matching Graph Layout

LeetCode Problem 3311 Difficulty: 🔴 Hard Topics: Array, Hash Table, Graph Theory, Matrix Solution Problem Understanding The problem gives us an undirected graph with n nodes labeled from 0 to n - 1 . We must place every node into a 2D grid so that adjacency in the grid matches adjacency in the graph exactly. Two cells are considered adjacent only if they share a side, meaning horizontal or vertical...

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LeetCode 3177 - Find the Maximum Length of a Good Subsequence II

LeetCode Problem 3177 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming Solution LeetCode 3177 - Find the Maximum Length of a Good Subsequence II Problem Understanding We are given an integer array nums and a non-negative integer k . We must find the maximum possible length of a subsequence such that the number of adjacent unequal pairs is at most k . A subsequence is formed by deleting zero...

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LeetCode 2202 - Maximize the Topmost Element After K Moves

LeetCode Problem 2202 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding In this problem, we are given a pile of integers represented as an array nums , where nums[0] is the current top element of the pile. We must perform exactly k moves, and in each move we are allowed to do one of two operations: Remove the current top element from the pile. Add back any previously removed...

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LeetCode 2607 - Make K-Subarray Sums Equal

LeetCode Problem 2607 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting, Number Theory Solution Problem Understanding The problem asks us to transform a circular integer array so that every subarray of length k has the same sum. A circular array means the end wraps around to the beginning, so subarrays can cross the boundary of the array. The allowed operation is increasing or decreasing any element by 1, and the...

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LeetCode 2567 - Minimum Score by Changing Two Elements

LeetCode Problem 2567 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to manipulate an array of integers, nums , in a very specific way to minimize a metric called the "score." The score is defined as the sum of two quantities: the high score , which is the maximum absolute difference between any two elements in the array, and the low score , which...

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LeetCode 1995 - Count Special Quadruplets

LeetCode Problem 1995 Difficulty: 🟢 Easy Topics: Array, Hash Table, Enumeration Solution Problem Understanding The problem asks us to count the number of distinct quadruplets (a, b, c, d) in a given array nums such that the sum of the first three elements equals the fourth, i.e., nums[a] + nums[b] + nums[c] == nums[d] , and the indices satisfy a < b < c < d . In simpler terms,...

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LeetCode 2125 - Number of Laser Beams in a Bank

LeetCode Problem 2125 Difficulty: 🟡 Medium Topics: Array, Math, String, Matrix Solution LeetCode 2125 - Number of Laser Beams in a Bank Problem Understanding The problem describes a bank floor plan as a binary matrix, represented by an array of strings. Each row corresponds to one row in the bank, and each character in the string represents a cell. A '1' means there is a security device installed in that...

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LeetCode 2280 - Minimum Lines to Represent a Line Chart

LeetCode Problem 2280 Difficulty: 🟡 Medium Topics: Array, Math, Geometry, Sorting, Number Theory Solution Problem Understanding In this problem, we are given a list of stock prices over different days. Each element in stockPrices is a pair: [day, price] This represents a point on a 2D graph where: The X-axis is the day The Y-axis is the stock price on that day The line chart is formed by connecting consecutive...

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LeetCode 2952 - Minimum Number of Coins to be Added

LeetCode Problem 2952 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to determine the minimum number of coins we need to add to an existing list of coins so that every integer from 1 to a given target can be formed as the sum of some subsequence of the coins. Here, a subsequence is a selection of coins in their original order, but we...

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LeetCode 3141 - Maximum Hamming Distances

LeetCode Problem 3141 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Breadth-First Search Solution Problem Understanding The problem asks us to compute the maximum Hamming distance for each element in an array of integers. The Hamming distance between two integers is defined as the number of positions where their binary representations differ. We are given an array nums and an integer m , and each element of nums is guaranteed to...

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LeetCode 2155 - All Divisions With the Highest Score of a Binary Array

LeetCode Problem 2155 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem gives us a binary array nums , meaning every element is either 0 or 1 . We are allowed to divide the array at any index i where 0 <= i <= n , and that division creates two parts: The left part contains elements from index 0 to i - 1 The right part contains elements...

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LeetCode 2763 - Sum of Imbalance Numbers of All Subarrays

LeetCode Problem 2763 Difficulty: 🔴 Hard Topics: Array, Hash Table, Enumeration Solution LeetCode 2763 - Sum of Imbalance Numbers of All Subarrays Problem Understanding For any array, its imbalance number is determined after sorting the elements. Suppose we have a subarray and sort it into sarr . We examine every adjacent pair in the sorted order. Whenever the difference between consecutive values is greater than 1 , that pair contributes...

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LeetCode 1852 - Distinct Numbers in Each Subarray

LeetCode Problem 1852 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 1852 - Distinct Numbers in Each Subarray Problem Understanding The problem gives us an integer array nums and an integer k . For every contiguous subarray of length k , we must determine how many unique values appear inside that window. A subarray is a continuous portion of the array. Since the window size is fixed...

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LeetCode 3259 - Maximum Energy Boost From Two Drinks

LeetCode Problem 3259 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding This problem is asking you to plan the consumption of two energy drinks over n hours to maximize the total energy boost. Each drink has a known energy contribution per hour, given by two arrays, energyDrinkA and energyDrinkB . You can drink only one energy drink per hour. However, if you switch from one drink to another,...

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LeetCode 1968 - Array With Elements Not Equal to Average of Neighbors

LeetCode Problem 1968 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to rearrange a distinct integer array so that no element is equal to the average of its neighbors . The input is a zero-indexed array nums of length at least 3, and all elements are guaranteed to be distinct. The output should be any valid rearrangement of nums that satisfies the condition for...

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LeetCode 3173 - Bitwise OR of Adjacent Elements

LeetCode Problem 3173 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us an integer array nums of length n . We must create and return a new array called answer of length n - 1 . For every index i , the value at answer[i] should be the result of applying the bitwise OR operation between two adjacent elements in the original array: $answer[i] =...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2661 - First Completely Painted Row or Column

LeetCode Problem 2661 Difficulty: 🟡 Medium Topics: Array, Hash Table, Matrix Solution Problem Understanding The problem is asking us to simulate a painting process on a 2D matrix. We are given a 1D array arr of integers and an m x n matrix mat , both containing all integers from 1 to m * n exactly once. For each integer in arr (in order), we "paint" the cell in mat...

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LeetCode 2654 - Minimum Number of Operations to Make All Array Elements Equal to 1

LeetCode Problem 2654 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution Problem Understanding The problem gives us an array of positive integers, nums . In one operation, we may choose two adjacent elements, nums[i] and nums[i+1] , and replace either one of them with the greatest common divisor, gcd , of the pair. The goal is to make every element in the array equal to 1 using the minimum...

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LeetCode 2788 - Split Strings by Separator

LeetCode Problem 2788 Difficulty: 🟢 Easy Topics: Array, String Solution LeetCode 2788 - Split Strings by Separator Problem Understanding This problem asks us to process an array of strings and split each string using a given separator character. After performing all splits, we must collect every resulting substring into a single output array while preserving the original order. More specifically, we are given: words , an array of strings. separator...

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LeetCode 3312 - Sorted GCD Pair Queries

LeetCode Problem 3312 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Binary Search, Combinatorics, Counting, Number Theory, Prefix Sum Solution === 1996-G1 === IMO 1996 Shortlist G1 Origin: GBR Problem Let triangle $ABC$ have orthocenter $H$, and let $P$ be a point on its circumcircle, distinct from $A$, $B$, $C$. Let $E$ be the foot of the altitude $BH$, let $PAQB$ and $PARC$ be parallelograms, and let $AQ$ meet $HR$...

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LeetCode 1983 - Widest Pair of Indices With Equal Range Sum

LeetCode Problem 1983 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to find the widest subarray (continuous segment) in two binary arrays nums1 and nums2 such that the sum of elements in that segment is equal for both arrays. Formally, we need to find indices (i, j) with i <= j such that: sum(nums1[i..j]) == sum(nums2[i..j]) and maximize the distance j -...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3218 - Minimum Cost for Cutting Cake I

LeetCode Problem 3218 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Dynamic Programming, Greedy, Sorting Solution Problem Understanding The problem gives us an m x n rectangular cake and asks us to cut it into individual 1 x 1 pieces. We are allowed to cut along predefined horizontal and vertical lines. Each line has a fixed cost associated with it. The important detail is that the same cut may need to...

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LeetCode 2768 - Number of Black Blocks

LeetCode Problem 2768 Difficulty: 🟡 Medium Topics: Array, Hash Table, Enumeration Solution Problem Understanding This problem asks us to count the number of 2 x 2 blocks in a grid based on how many black cells they contain. We are given the dimensions of a grid, m rows and n columns, and a list of coordinates representing black cells. Every cell not listed is white. A block is a 2...

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LeetCode 2656 - Maximum Sum With Exactly K Elements

LeetCode Problem 2656 Difficulty: 🟢 Easy Topics: Array, Greedy Solution LeetCode 2656 - Maximum Sum With Exactly K Elements Problem Understanding The problem gives us an integer array nums and an integer k . We must perform exactly k operations. During each operation, we choose one element from the array, add its value to our score, remove it from the array, and then insert a new element equal to the...

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LeetCode 3153 - Sum of Digit Differences of All Pairs

LeetCode Problem 3153 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Counting Solution Problem Understanding The problem asks us to compute the total digit difference across every pair of numbers in the array. All numbers have the same number of digits. For any two numbers, their digit difference is defined as the number of positions where the digits are different. For example: 13 and 23 differ only at the first...

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LeetCode 2440 - Create Components With Same Value

LeetCode Problem 2440 Difficulty: 🔴 Hard Topics: Array, Math, Tree, Depth-First Search, Enumeration Solution Problem Understanding This problem is asking us to take an undirected tree where each node has a numerical value and determine how many edges we can remove such that every resulting connected component has the same total value. The tree is represented by a list of node values nums and a list of edges edges that...

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LeetCode 1901 - Find a Peak Element II

LeetCode Problem 1901 Difficulty: 🟡 Medium Topics: Array, Binary Search, Matrix Solution Problem Understanding The problem requires finding a peak element in a 2D matrix. A peak element is defined as an element that is strictly greater than its adjacent neighbors to the top, bottom, left, and right. The matrix is guaranteed to have no two adjacent elements equal, which simplifies comparisons. The input is a 2D list mat of...

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LeetCode 3347 - Maximum Frequency of an Element After Performing Operations II

LeetCode Problem 3347 Difficulty: 🔴 Hard Topics: Array, Binary Search, Sliding Window, Sorting, Prefix Sum Solution LeetCode 3347 - Maximum Frequency of an Element After Performing Operations II Problem Understanding The problem gives us an integer array nums , along with two integers, k and numOperations . We are allowed to perform exactly numOperations operations. In each operation: We must choose an index that has not been used before. We...

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LeetCode 1948 - Delete Duplicate Folders in System

LeetCode Problem 1948 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Trie, Hash Function Solution Problem Understanding The problem gives a hierarchical file system represented as a list of absolute paths, where each path is an array of folder names from the root to a leaf folder. From these paths, we must reconstruct the implicit tree structure of folders, where each node represents a folder and edges represent parent-child relationships....

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LeetCode 3175 - Find The First Player to win K Games in a Row

LeetCode Problem 3175 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding The problem describes a competition where players stand in a queue and repeatedly compete against each other. Every player has a unique skill value, and whenever two players play, the one with the larger skill always wins. At each step: The first two players in the queue compete. The stronger player stays at the front. The weaker player...

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LeetCode 3379 - Transformed Array

LeetCode Problem 3379 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding The problem asks us to transform a given integer array nums into a new array result following specific movement rules. Each element in nums determines how many steps to move in a circular manner, either to the right (if positive) or left (if negative). Zero values remain unchanged. The circular array property means that moving past the last...

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LeetCode 3078 - Match Alphanumerical Pattern in Matrix I

LeetCode Problem 3078 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Matrix Solution LeetCode 3078 - Match Alphanumerical Pattern in Matrix I Problem Understanding This problem asks us to search for a rectangular submatrix inside a larger integer matrix, where the submatrix follows a pattern described by digits and lowercase letters. The input consists of: board , a 2D matrix of integers from 0 to 9 pattern , a 2D...

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LeetCode 2133 - Check if Every Row and Column Contains All Numbers

LeetCode Problem 2133 Difficulty: 🟢 Easy Topics: Array, Hash Table, Matrix Solution Problem Understanding In this problem, we are given an n x n matrix where every value is guaranteed to be between 1 and n . A matrix is considered valid if every row contains all integers from 1 through n exactly once, and every column also contains all integers from 1 through n exactly once. Another way to...

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LeetCode 2435 - Paths in Matrix Whose Sum Is Divisible by K

LeetCode Problem 2435 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to count the number of paths in a 2D integer matrix from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) such that the sum of the values along the path is divisible by a given integer k . Movement is restricted to only down or...

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LeetCode 3180 - Maximum Total Reward Using Operations I

LeetCode Problem 3180 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to maximize a running total reward by selecting elements from an integer array rewardValues . Each element in the array represents a reward at that index. Initially, the total reward x is 0, and no indices are marked. The allowed operation is to select an unmarked index i and add its value rewardValues[i]...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2121 - Intervals Between Identical Elements

LeetCode Problem 2121 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution LeetCode 2121 - Intervals Between Identical Elements Problem Statement You are given a 0-indexed integer array arr . For every index i , you must compute the sum of distances between i and every other index j where arr[i] == arr[j] . The distance between two indices is the absolute difference of their positions: $$|i - j|$$...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2580 - Count Ways to Group Overlapping Ranges

LeetCode Problem 2580 Difficulty: 🟡 Medium Topics: Array, Sorting Solution Problem Understanding The problem gives us a list of integer ranges, where each range represents all integers between start and end , inclusive. We must divide all ranges into exactly two groups. Either group may be empty. The important restriction is that overlapping ranges cannot be separated. If two ranges share at least one common integer, they must belong to...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2090 - K Radius Subarray Averages

LeetCode Problem 2090 Difficulty: 🟡 Medium Topics: Array, Sliding Window Solution Problem Understanding The problem asks us to compute a special average for every index in the array. For each position i , we want to look at a subarray centered at i with radius k . That means we include all elements from index i - k through i + k , inclusive. The size of this window is...

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LeetCode 3256 - Maximum Value Sum by Placing Three Rooks I

LeetCode Problem 3256 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix, Enumeration Solution Problem Understanding We are given an m x n matrix called board , where each cell contains an integer value. We must place exactly three rooks on the board. A rook attacks every square in the same row and the same column. Therefore, for three rooks to be valid: No two rooks can share the same row...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2682 - Find the Losers of the Circular Game

LeetCode Problem 2682 Difficulty: 🟢 Easy Topics: Array, Hash Table, Simulation Solution Problem Understanding This problem describes a circular passing game among n friends numbered from 1 to n . The ball always starts with friend 1 , and each turn increases the number of clockwise steps by a multiple of k . More specifically: On the first turn, the current player passes the ball 1 * k steps clockwise....

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LeetCode 2444 - Count Subarrays With Fixed Bounds

LeetCode Problem 2444 Difficulty: 🔴 Hard Topics: Array, Queue, Sliding Window, Monotonic Queue Solution Problem Understanding This problem asks us to count how many contiguous subarrays satisfy two exact boundary conditions at the same time: The minimum element in the subarray must be exactly minK . The maximum element in the subarray must be exactly maxK . The key detail is that these are exact matches , not inequalities. A...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2615 - Sum of Distances

LeetCode Problem 2615 Difficulty: 🟡 Medium Topics: Array, Hash Table, Prefix Sum Solution Problem Understanding The problem asks us to compute, for every index i in the array nums , the total distance between i and every other index j where nums[j] == nums[i] . More formally, for each position i , we need to calculate: $$\sum |i - j|$$ for all indices j such that: nums[j] == nums[i] j...

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LeetCode 1967 - Number of Strings That Appear as Substrings in Word

LeetCode Problem 1967 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding The problem asks us to determine how many strings in the array patterns appear as substrings within a given string word . A substring is defined as a contiguous sequence of characters, meaning the characters must appear in order and without gaps inside word . We are given two inputs. The first input, patterns , is a list...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2808 - Minimum Seconds to Equalize a Circular Array

LeetCode Problem 2808 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution Problem Understanding The problem gives a circular array nums of length n . At each second, every element in the array can be replaced simultaneously by either itself, its previous neighbor, or its next neighbor. The task is to determine the minimum number of seconds required to make all elements equal. In simpler terms, the array elements "propagate" their...

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LeetCode 3189 - Minimum Moves to Get a Peaceful Board

LeetCode Problem 3189 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Counting Sort Solution Problem Understanding In this problem, we are given the positions of n rooks placed on an n x n chessboard. Each rook is represented as a pair [xi, yi] , where xi is the row index and yi is the column index. A peaceful board is defined as a board where: Every row contains exactly one rook...

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LeetCode 2122 - Recover the Original Array

LeetCode Problem 2122 Difficulty: 🔴 Hard Topics: Array, Hash Table, Two Pointers, Sorting, Enumeration Solution Problem Understanding The problem presents a scenario in which Alice has an original array arr of length n consisting of positive integers. She chooses a positive integer k and generates two new arrays: lower and higher . The array lower is formed by subtracting k from each element of arr , while higher is formed...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2901 - Longest Unequal Adjacent Groups Subsequence II

LeetCode Problem 2901 Difficulty: 🟡 Medium Topics: Array, String, Dynamic Programming Solution Problem Understanding The problem asks us to select the longest subsequence of words from a given array such that adjacent words in the subsequence satisfy two conditions: first, their corresponding groups values are different , and second, the words are of the same length and differ by exactly one character (hamming distance = 1). In other words, we...

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LeetCode 2149 - Rearrange Array Elements by Sign

LeetCode Problem 2149 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Simulation Solution Problem Understanding The problem asks us to rearrange a given integer array nums such that positive and negative numbers alternate, starting with a positive number. The array has an even length and contains an equal number of positive and negative integers. In addition to alternating signs, the relative order of positive numbers among themselves and negative numbers among...

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LeetCode 2900 - Longest Unequal Adjacent Groups Subsequence I

LeetCode Problem 2900 Difficulty: 🟢 Easy Topics: Array, String, Dynamic Programming, Greedy Solution LeetCode 2900 - Longest Unequal Adjacent Groups Subsequence I Problem Understanding We are given two arrays of the same length: words[i] is a string. groups[i] is either 0 or 1 . We want to select a subsequence of words . A subsequence preserves the original order of elements, but we may skip any number of elements. The...

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LeetCode 2085 - Count Common Words With One Occurrence

LeetCode Problem 2085 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Counting Solution LeetCode 2085, Count Common Words With One Occurrence Problem Understanding This problem gives us two arrays of strings, words1 and words2 . Our task is to count how many strings appear exactly once in both arrays. The key detail is that a word only qualifies if: It appears exactly one time in words1 It appears exactly one...

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LeetCode 2920 - Maximum Points After Collecting Coins From All Nodes

LeetCode Problem 2920 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search, Memoization Solution LeetCode 2920 - Maximum Points After Collecting Coins From All Nodes Problem Understanding We are given a tree with n nodes rooted at node 0 . Each node contains a certain number of coins. We must collect coins from every node while respecting the tree hierarchy, meaning a node can only be processed...

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LeetCode 2491 - Divide Players Into Teams of Equal Skill

LeetCode Problem 2491 Difficulty: 🟡 Medium Topics: Array, Hash Table, Two Pointers, Sorting Solution Problem Understanding This problem asks us to divide a given list of player skill levels into teams of exactly two players such that every team has the same total skill . The chemistry of a team is defined as the product of the skills of the two players, and we are asked to return the sum...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2212 - Maximum Points in an Archery Competition

LeetCode Problem 2212 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem is asking us to determine the optimal way for Bob to distribute his numArrows across 12 scoring sections (from 0 to 11) in an archery competition in order to maximize his total points against Alice. Alice's arrow distribution is given in aliceArrows . The scoring rules are such that for each section, the...

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LeetCode 1985 - Find the Kth Largest Integer in the Array

LeetCode Problem 1985 Difficulty: 🟡 Medium Topics: Array, String, Divide and Conquer, Sorting, Heap (Priority Queue), Quickselect Solution Problem Understanding This problem asks us to find the kth largest value among a list of integers that are represented as strings. Each element in nums is a non-negative integer encoded as a string with no leading zeros, and we are required to return the kth largest value according to numeric order,...

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LeetCode 2541 - Minimum Operations to Make Array Equal II

LeetCode Problem 2541 Difficulty: 🟡 Medium Topics: Array, Math, Greedy Solution

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LeetCode 2274 - Maximum Consecutive Floors Without Special Floors

LeetCode Problem 2274 Difficulty: 🟡 Medium Topics: Array, Sorting Solution LeetCode 2274 - Maximum Consecutive Floors Without Special Floors Problem Understanding The problem gives us a range of rented floors in a building, from bottom to top , inclusive. Within this range, some floors are marked as special floors and cannot be counted as regular office floors. Our task is to determine the largest number of consecutive floors that do...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2951 - Find the Peaks

LeetCode Problem 2951 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution Problem Understanding The problem is asking us to identify all the peaks in a given array mountain . A peak is an element that is strictly greater than its immediate neighbors. Importantly, the first and last elements of the array cannot be peaks because they do not have two neighbors. The input is a zero-indexed array of integers mountain with...

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LeetCode 3387 - Maximize Amount After Two Days of Conversions

LeetCode Problem 3387 Difficulty: 🟡 Medium Topics: Array, String, Depth-First Search, Breadth-First Search, Graph Theory Solution LeetCode 3387 - Maximize Amount After Two Days of Conversions Problem Understanding This problem models currency conversions as graph traversal across two separate days. You begin with exactly 1.0 unit of initialCurrency , and you may perform any number of exchanges on day 1 using the first set of conversion rates, followed by any...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2044 - Count Number of Maximum Bitwise-OR Subsets

LeetCode Problem 2044 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to examine every possible non-empty subset of the given array nums and compute the bitwise OR value of each subset. Among all these OR values, we need to determine the maximum possible value, then count how many different subsets produce that maximum. A subset is formed by selecting any combination of...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2556 - Disconnect Path in a Binary Matrix by at Most One Flip

LeetCode Problem 2556 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Depth-First Search, Breadth-First Search, Matrix Solution Problem Understanding The problem is asking whether it is possible to disconnect a path from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) in a binary matrix by flipping at most one cell from 1 to 0 or 0 to 1 . A path only allows moves...

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LeetCode 2170 - Minimum Operations to Make the Array Alternating

LeetCode Problem 2170 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding The problem requires transforming a given integer array nums into an alternating array with the minimum number of operations. An array is alternating if elements at even indices repeat every two steps ( nums[i] == nums[i-2] for i >= 2 ) and elements at odd indices differ from their previous element ( nums[i] != nums[i-1]...

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LeetCode 2510 - Check if There is a Path With Equal Number of 0's And 1's

LeetCode Problem 2510 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to determine if there exists a path in a binary matrix from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) such that the number of 0 s visited along the path is equal to the number of 1 s. The matrix is binary , so...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1828 - Queries on Number of Points Inside a Circle

LeetCode Problem 1828 Difficulty: 🟡 Medium Topics: Array, Math, Geometry Solution Problem Understanding This problem gives us two collections of geometric objects on a 2D plane. The first collection is an array called points , where each element is a coordinate pair [x, y] . Each pair represents a point on the plane. Multiple points are allowed to have the exact same coordinates, so duplicates must be counted separately. The...

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LeetCode 2966 - Divide Array Into Arrays With Max Difference

LeetCode Problem 2966 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem asks us to divide an integer array nums of size n (where n is guaranteed to be a multiple of 3) into smaller arrays of exactly size 3, such that within each array, the difference between the largest and smallest element does not exceed a given integer k . The goal is to return a...

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LeetCode 2135 - Count Words Obtained After Adding a Letter

LeetCode Problem 2135 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Bit Manipulation, Sorting Solution Problem Understanding The problem requires us to determine how many strings in targetWords can be formed from strings in startWords through a specific transformation. The transformation involves two operations: appending a single letter not already present in the string, and then rearranging all letters arbitrarily. Essentially, we are checking whether, by adding one new character...

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LeetCode 2064 - Minimized Maximum of Products Distributed to Any Store

LeetCode Problem 2064 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy Solution Problem Understanding The problem gives us n retail stores and an array quantities , where each element represents how many products exist for a particular product type. The important restriction is that a single store may contain products from only one product type. However, a product type may be split across multiple stores. Our goal is to distribute...

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LeetCode 3244 - Shortest Distance After Road Addition Queries II

LeetCode Problem 3244 Difficulty: 🔴 Hard Topics: Array, Greedy, Graph Theory, Ordered Set Solution Problem Understanding The problem presents a sequence of n cities numbered from 0 to n - 1 with an initial chain of unidirectional roads such that city i is connected to city i + 1 for all valid i . You are given a list of queries where each query adds a new road from city...

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LeetCode 3314 - Construct the Minimum Bitwise Array I

LeetCode Problem 3314 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to construct an array ans from a given array nums of prime integers. For each element nums[i] , we need to find the smallest integer ans[i] such that the bitwise OR of ans[i] and ans[i] + 1 equals nums[i] . Formally, ans[i] | (ans[i] + 1) == nums[i] . If no such ans[i]...

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LeetCode 3195 - Find the Minimum Area to Cover All Ones I

LeetCode Problem 3195 Difficulty: 🟡 Medium Topics: Array, Matrix Solution Problem Understanding The problem asks us to find the smallest rectangle that covers all the 1's in a given 2D binary grid. The grid consists of rows and columns where each cell is either 0 or 1. The rectangle must have sides aligned with the grid axes, meaning its edges run along the rows and columns. The goal is to...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2100 - Find Good Days to Rob the Bank

LeetCode Problem 2100 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem asks us to find all days that are "good" for robbing a bank based on the number of guards on duty over a period of days. You are given an array security where each element represents the number of guards on a specific day, and an integer time that defines a window before...

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LeetCode 2195 - Append K Integers With Minimal Sum

LeetCode Problem 2195 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Sorting Solution Problem Understanding The problem asks us to append k unique positive integers to an existing array nums such that none of the integers we add are already in nums , and the sum of the numbers we append is minimized. In other words, we want to pick the smallest k positive integers that are missing from nums ....

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2708 - Maximum Strength of a Group

LeetCode Problem 2708 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Greedy, Bit Manipulation, Sorting, Enumeration Solution Problem Understanding The problem asks us to select a non-empty subset of integers from a given array nums such that the product of the numbers in the subset is maximized. Each number represents a student’s exam score, and the subset represents a group of students. The "strength" of a group is the product...

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LeetCode 2113 - Elements in Array After Removing and Replacing Elements

LeetCode Problem 2113 Difficulty: 🟡 Medium Topics: Array Solution Problem Understanding The problem describes an array that continuously goes through a repeating two-phase process. At minute 0 , the array is unchanged. Every following minute, the leftmost element is removed until the array becomes empty. Once the array is empty, elements are added back one by one to the end of the array in the exact order they were removed....

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LeetCode 3098 - Find the Sum of Subsequence Powers

LeetCode Problem 3098 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Sorting Solution Problem Understanding The problem asks us to compute the sum of powers of all subsequences of length k from an array nums . A subsequence is any subset of elements taken in order from the array without reordering. The power of a subsequence is defined as the minimum absolute difference between any two elements in that subsequence. We...

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LeetCode 3020 - Find the Maximum Number of Elements in Subset

LeetCode Problem 3020 Difficulty: 🟡 Medium Topics: Array, Hash Table, Enumeration Solution Problem Understanding The problem gives us an array of positive integers and asks us to choose the largest possible subset that can be rearranged into a very specific symmetric structure. The required structure looks like this: $$[x, x^2, x^4, \dots, x^{k/2}, x^k, x^{k/2}, \dots, x^4, x^2, x]$$ where $k$ is a power of two. The sequence grows by...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2367 - Number of Arithmetic Triplets

LeetCode Problem 2367 Difficulty: 🟢 Easy Topics: Array, Hash Table, Two Pointers, Enumeration Solution Problem Understanding The problem requires us to find the number of arithmetic triplets in a strictly increasing array of integers. An arithmetic triplet (i, j, k) satisfies the conditions i < j < k , nums[j] - nums[i] == diff , and nums[k] - nums[j] == diff . Essentially, we are looking for sequences of three...

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LeetCode 2185 - Counting Words With a Given Prefix

LeetCode Problem 2185 Difficulty: 🟢 Easy Topics: Array, String, String Matching Solution Problem Understanding The problem gives us two inputs: An array of strings called words A string called pref We must count how many strings inside words start with the string pref . A prefix means the beginning portion of a string. For example: "at" is a prefix of "attention" "pay" is a prefix of "pay" "code" is not...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2054 - Two Best Non-Overlapping Events

LeetCode Problem 2054 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us a list of events, where each event is represented as: [startTime, endTime, value] Each event occupies an inclusive time interval from startTime to endTime . If we attend that event, we earn value points. We are allowed to attend at most two events, but the chosen events...

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LeetCode 2270 - Number of Ways to Split Array

LeetCode Problem 2270 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem asks us to determine the number of ways to split a given 0-indexed array nums into two non-empty contiguous subarrays such that the sum of the first part is greater than or equal to the sum of the second part. Formally, a split at index i is valid if sum(nums[0:i+1]) >= sum(nums[i+1:n]) and 0 <=...

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LeetCode 2553 - Separate the Digits in an Array

LeetCode Problem 2553 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding This problem asks us to take an array of positive integers, nums , and transform it into another array, answer , where each element of nums is broken down into its constituent digits in order. The key requirement is that the order of the digits must reflect the original numbers’ order in the array. For example, if a...

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LeetCode 2670 - Find the Distinct Difference Array

LeetCode Problem 2670 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem asks us to compute the distinct difference array for a given integer array nums . For each index i in the array, we calculate the difference between the number of distinct elements in the prefix nums[0, ..., i] and the number of distinct elements in the suffix nums[i + 1, ..., n - 1] ....

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LeetCode 2766 - Relocate Marbles

LeetCode Problem 2766 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting, Simulation Solution Problem Understanding The problem gives us an array nums representing the positions of marbles on a number line. Multiple marbles may exist at the same position, so nums can contain duplicates. We are also given two arrays, moveFrom and moveTo , which describe a sequence of move operations. For each index i , we must move every...

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LeetCode 2198 - Number of Single Divisor Triplets

LeetCode Problem 2198 Difficulty: 🟡 Medium Topics: Array, Counting, Enumeration Solution Problem Understanding The problem asks us to count how many ordered triplets of distinct indices (i, j, k) satisfy a very specific divisibility condition. For every triplet, we compute: $$\text{sum} = nums[i] + nums[j] + nums[k]$$ The triplet is considered valid if this sum is divisible by exactly one of the three participating values: nums[i] nums[j] nums[k] The indices...

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LeetCode 2463 - Minimum Total Distance Traveled

LeetCode Problem 2463 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Sorting Solution Here is a comprehensive, reference-quality solution guide for LeetCode 2463 - Minimum Total Distance Traveled following your formatting requirements. Problem Understanding The problem gives us a set of robots on an X-axis, each at a unique position, and a set of factories, each at a unique position with a maximum capacity of robots it can repair. Robots are...

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LeetCode 2509 - Cycle Length Queries in a Tree

LeetCode Problem 2509 Difficulty: 🔴 Hard Topics: Array, Tree, Binary Tree Solution Problem Understanding The problem gives us a complete binary tree where nodes are labeled in the same way as a binary heap. For every node with value x : Its left child is 2 * x Its right child is 2 * x + 1 The tree contains all node values from 1 to 2^n - 1 ....

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LeetCode 1861 - Rotating the Box

LeetCode Problem 1861 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Matrix Solution Please provide the specific problem number/title you want the detailed solution guide for (for example, “LeetCode 1861 - Rotating the Box”), and I will format it exactly according to your requirements.

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LeetCode 2071 - Maximum Number of Tasks You Can Assign

LeetCode Problem 2071 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Greedy, Queue, Sorting, Monotonic Queue Solution Problem Understanding This problem asks us to maximize the number of tasks that can be completed using a group of workers, where each worker can perform at most one task. Each task has a required strength value, and each worker has a current strength value. A worker can complete a task if...

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LeetCode 3282 - Reach End of Array With Max Score

LeetCode Problem 3282 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 3282 - Reach End of Array With Max Score Problem Understanding We are given an integer array nums , where each position represents a possible jump starting point. We begin at index 0 and must eventually reach index n - 1 . From any index i , we may jump to any later index j where j > i...

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LeetCode 2446 - Determine if Two Events Have Conflict

LeetCode Problem 2446 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding The problem asks us to determine if two events on the same day overlap in time. Each event is given as a pair of strings in HH:MM format representing the start and end times. The output should be a boolean: true if there is any overlap between the two events, and false otherwise. The input guarantees that the...

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LeetCode 3289 - The Two Sneaky Numbers of Digitville

LeetCode Problem 3289 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math Solution Problem Understanding The problem is asking us to identify two numbers that appear twice in an otherwise consecutive list of integers ranging from 0 to n - 1 . In other words, the input nums is almost a permutation of the numbers 0 through n - 1 , except that two numbers are repeated , so the length...

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LeetCode 2061 - Number of Spaces Cleaning Robot Cleaned

LeetCode Problem 2061 Difficulty: 🟡 Medium Topics: Array, Matrix, Simulation Solution Problem Understanding In this problem, we are given a 2D binary matrix called room . Each cell represents a position in the room: 0 means the space is empty and can be cleaned. 1 means the space contains an object and cannot be entered. A cleaning robot starts at the top-left corner (0, 0) , and the problem guarantees...

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LeetCode 3192 - Minimum Operations to Make Binary Array Elements Equal to One II

LeetCode Problem 3192 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Greedy Solution Problem Understanding This problem asks us to take a binary array nums , which contains only 0s and 1s, and transform it so that all elements become 1 using the minimum number of allowed operations. The operation is defined as choosing any index i and flipping all elements from that index to the end of the array. Flipping...

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LeetCode 3093 - Longest Common Suffix Queries

LeetCode Problem 3093 Difficulty: 🔴 Hard Topics: Array, String, Trie Solution Problem Understanding The problem asks us to process a set of suffix matching queries efficiently. We are given two arrays: wordsContainer , which contains candidate strings wordsQuery , which contains query strings For every query string, we must find the index of the string in wordsContainer that shares the longest common suffix with that query. A suffix is the...

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LeetCode 2459 - Sort Array by Moving Items to Empty Space

LeetCode Problem 2459 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sorting Solution Problem Understanding The array contains every integer from 0 to n - 1 exactly once. The value 0 represents the empty space, while every other number represents an item that should eventually appear in sorted order. The operation is unusual compared to normal array sorting problems. In one move, we may take any item and place it into...

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LeetCode 2277 - Closest Node to Path in Tree

LeetCode Problem 2277 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Breadth-First Search Solution Problem Understanding The problem is asking us to process queries on a tree structure. Each query gives a path between two nodes starti and endi and a third node nodei . We are asked to find which node along the path is closest to nodei in terms of the number of edges separating them, also known...

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LeetCode 2817 - Minimum Absolute Difference Between Elements With Constraint

LeetCode Problem 2817 Difficulty: 🟡 Medium Topics: Array, Binary Search, Ordered Set Solution LeetCode 2817 - Minimum Absolute Difference Between Elements With Constraint Problem Understanding We are given an integer array nums and an integer x . We need to find two elements whose indices are separated by at least x , and among all such valid pairs, return the minimum possible absolute difference between their values. More formally, we...

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LeetCode 1887 - Reduction Operations to Make the Array Elements Equal

LeetCode Problem 1887 Difficulty: 🟡 Medium Topics: Array, Sorting Solution Problem Understanding This problem asks us to make all elements in an integer array equal by repeatedly reducing the largest elements to the next largest element in the array. The input is an array nums of integers, where each operation requires identifying the current largest element and reducing it to the value of the next largest element strictly smaller than...

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LeetCode 2596 - Check Knight Tour Configuration

LeetCode Problem 2596 Difficulty: 🟡 Medium Topics: Array, Depth-First Search, Breadth-First Search, Matrix, Simulation Solution Problem Understanding The problem gives us an n x n matrix called grid , where every number from 0 to n * n - 1 appears exactly once. Each value represents the order in which a knight visited that cell during a tour of the chessboard. A knight in chess moves in an L-shape. From...

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LeetCode 2425 - Bitwise XOR of All Pairings

LeetCode Problem 2425 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Brainteaser Solution Problem Understanding The problem gives us two arrays, nums1 and nums2 , and asks us to compute the XOR of every possible pair formed between the two arrays. For every element in nums1 , we pair it with every element in nums2 exactly once. Each pair produces a value using the bitwise XOR operation: nums1[i] ^ nums2[j] If...

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LeetCode 2832 - Maximal Range That Each Element Is Maximum in It

LeetCode Problem 2832 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution LeetCode 2832 - Maximal Range That Each Element Is Maximum in It Problem Understanding We are given an array nums consisting of distinct integers. For every position i , we need to determine the maximum possible length of a contiguous subarray in which nums[i] is the largest element. More formally, for each index i , we want to...

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LeetCode 2073 - Time Needed to Buy Tickets

LeetCode Problem 2073 Difficulty: 🟢 Easy Topics: Array, Queue, Simulation Solution Problem Understanding This problem describes a queue of n people, each wanting to buy a certain number of tickets. The input is an array tickets where tickets[i] represents how many tickets the i-th person wants. The process works like a real-life queue: each person buys one ticket at a time , taking exactly 1 second per ticket , and...

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LeetCode 2464 - Minimum Subarrays in a Valid Split

LeetCode Problem 2464 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Number Theory Solution Problem Understanding The problem asks us to split an array of integers nums into contiguous subarrays such that each subarray satisfies a validity condition : the greatest common divisor (GCD) of the first and last elements of the subarray must be strictly greater than 1. Each element in nums must belong to exactly one subarray. Our...

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LeetCode 2614 - Prime In Diagonal

LeetCode Problem 2614 Difficulty: 🟢 Easy Topics: Array, Math, Matrix, Number Theory Solution Problem Understanding The problem gives us a square matrix nums of size n x n . We need to examine the values that appear on the two diagonals of the matrix and return the largest value among them that is prime. There are two diagonals in a square matrix: The primary diagonal contains elements where the row...

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LeetCode 3326 - Minimum Division Operations to Make Array Non Decreasing

LeetCode Problem 3326 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Number Theory Solution Problem Understanding The problem asks us to make a given integer array nums non-decreasing by performing a specific type of operation any number of times. Each operation consists of selecting an element and dividing it by its greatest proper divisor . A proper divisor of a number x is a positive integer less than x that divides...

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LeetCode 2761 - Prime Pairs With Target Sum

LeetCode Problem 2761 Difficulty: 🟡 Medium Topics: Array, Math, Enumeration, Number Theory Solution Problem Understanding The problem asks us to find all pairs of prime numbers (x, y) such that both numbers are between 1 and n inclusive, their sum equals n , and x <= y . The input is a single integer n , and the output is a sorted list of pairs [x, y] meeting these conditions,...

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LeetCode 2996 - Smallest Missing Integer Greater Than Sequential Prefix Sum

LeetCode Problem 2996 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting Solution Problem Understanding The problem asks us to find the smallest missing integer in the array that is greater than or equal to the sum of the longest sequential prefix . A sequential prefix means the beginning part of the array where every number increases by exactly 1 compared to the previous number. Formally, for a prefix nums[0..i] ,...

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LeetCode 2644 - Find the Maximum Divisibility Score

LeetCode Problem 2644 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to identify, from a list of divisors, the integer that has the maximum divisibility score with respect to a given array of numbers. The divisibility score of a divisor is defined as the count of elements in nums that are divisible by that divisor. In simpler terms, for each divisor, we count how many numbers...

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LeetCode 2166 - Design Bitset

LeetCode Problem 2166 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design Solution Problem Understanding This problem asks us to design a custom Bitset data structure that supports several operations efficiently. A bitset is simply a sequence of binary values, where each position stores either 0 or 1 . We are given a fixed size during initialization, and initially every bit is set to 0 . After that, the class...

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LeetCode 3169 - Count Days Without Meetings

LeetCode Problem 3169 Difficulty: 🟡 Medium Topics: Array, Sorting Solution LeetCode 3169 - Count Days Without Meetings Problem Understanding The problem gives us a total number of working days, numbered from 1 to days , along with a list of meeting intervals. Each interval [start, end] represents a meeting that occupies every day from start through end , inclusive. Our task is to determine how many days remain completely free,...

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LeetCode 1937 - Maximum Number of Points with Cost

LeetCode Problem 1937 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem gives us an m x n matrix called points . We must choose exactly one cell from every row. The value of the chosen cell is added to our score. However, there is a movement penalty between consecutive rows. If we choose column c1 in row r and column c2 in row r +...

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LeetCode 2365 - Task Scheduler II

LeetCode Problem 2365 Difficulty: 🟡 Medium Topics: Array, Hash Table, Simulation Solution Problem Understanding The problem gives us an array tasks , where each value represents a task type. The tasks must be completed strictly in the given order, which means we cannot rearrange them to optimize the schedule. We are also given an integer space . After completing a task of a certain type, we must wait at least...

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LeetCode 2573 - Find the String with LCP

LeetCode Problem 2573 Difficulty: 🔴 Hard Topics: Array, String, Dynamic Programming, Greedy, Union-Find, Matrix Solution Problem Understanding The problem gives us an n x n matrix called lcp , where: lcp[i][j] represents the length of the longest common prefix between: the suffix starting at index i the suffix starting at index j If the unknown string is word , then: suffix i is word[i:] suffix j is word[j:] The task...

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LeetCode 2992 - Number of Self-Divisible Permutations

LeetCode Problem 2992 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Backtracking, Bit Manipulation, Number Theory, Bitmask Solution Problem Understanding The problem asks us to count how many permutations of the numbers 1 through n satisfy a special condition called self-divisible. We start with the array: [1, 2, 3, ..., n] We must rearrange these numbers into every possible permutation, then determine whether the permutation is valid. A permutation a...

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LeetCode 3197 - Find the Minimum Area to Cover All Ones II

LeetCode Problem 3197 Difficulty: 🔴 Hard Topics: Array, Matrix, Enumeration Solution Problem Understanding The problem gives us a binary matrix grid , where each cell contains either 0 or 1 . Our goal is to place exactly three non-overlapping axis-aligned rectangles so that every cell containing 1 is covered by at least one rectangle. Each rectangle must satisfy several conditions: Its sides must be parallel to the grid axes. It...

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LeetCode 2499 - Minimum Total Cost to Make Arrays Unequal

LeetCode Problem 2499 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Counting Solution Problem Understanding You are given two arrays, nums1 and nums2 , both of length n . You are allowed to perform operations only on nums1 . In a single operation, you may swap any two indices in nums1 , and the cost of that operation is the sum of the two indices involved in the swap. The...

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LeetCode 2451 - Odd String Difference

LeetCode Problem 2451 Difficulty: 🟢 Easy Topics: Array, Hash Table, String Solution LeetCode 2451 - Odd String Difference Problem Understanding The problem gives us an array of strings where every string has the same length. For each string, we construct a difference array by subtracting the alphabet position of consecutive characters. For example, the string "adc" produces: 'd' - 'a' = 3 'c' - 'd' = -1 So its difference...

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LeetCode 2404 - Most Frequent Even Element

LeetCode Problem 2404 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to identify the most frequent even number in an integer array nums . If multiple even numbers share the highest frequency, we should return the smallest among them. If the array contains no even numbers, the function should return -1 . The input array nums can have up to 2000 elements, each...

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LeetCode 3041 - Maximize Consecutive Elements in an Array After Modification

LeetCode Problem 3041 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Sorting Solution Problem Understanding The problem is asking us to maximize the number of consecutive integers we can select from an array after we are allowed to increase any element by at most 1 . The input array nums contains positive integers and can have up to 10^5 elements, with each element ranging from 1 to 10^6 . The output...

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LeetCode 1936 - Add Minimum Number of Rungs

LeetCode Problem 1936 Difficulty: 🟡 Medium Topics: Array, Greedy Solution Problem Understanding The problem gives us a ladder represented by a strictly increasing array called rungs . Each value in the array represents the height of a rung above the floor. You begin standing on the floor at height 0 , and your goal is to reach the final rung. The restriction is that you can only climb upward if...

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LeetCode 3366 - Minimum Array Sum

LeetCode Problem 3366 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding We are given an array nums and two different operations that can reduce the values of elements in the array. The first operation divides a number by 2 and rounds the result upward. This operation can only be used at most op1 times globally, and each array index can receive this operation at most once. The second...

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LeetCode 2421 - Number of Good Paths

LeetCode Problem 2421 Difficulty: 🔴 Hard Topics: Array, Hash Table, Tree, Union-Find, Graph Theory, Sorting Solution Problem Understanding The problem is asking us to count the number of good paths in a tree. A tree is a connected acyclic graph with n nodes and n - 1 edges. Each node has an integer value assigned by the array vals . A good path is defined as a simple path (no...

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LeetCode 2183 - Count Array Pairs Divisible by K

LeetCode Problem 2183 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Counting, Number Theory Solution Problem Understanding The problem gives us an integer array nums and an integer k . We must count how many index pairs (i, j) satisfy two conditions: i < j nums[i] * nums[j] is divisible by k In other words, for every pair of distinct elements in the array, we check whether their product contains...

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LeetCode 2980 - Check if Bitwise OR Has Trailing Zeros

LeetCode Problem 2980 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to determine whether we can select two or more elements from a given array of positive integers such that their bitwise OR produces a number whose binary representation ends with at least one zero . In other words, the least significant bit of the OR result should be 0 . The input is...

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LeetCode 2218 - Maximum Value of K Coins From Piles

LeetCode Problem 2218 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding This problem asks us to maximize the total value of coins collected from multiple piles while following a strict removal rule. Each pile is ordered from top to bottom, meaning we cannot arbitrarily pick any coin in a pile. We may only remove coins from the top, one at a time. If we want a...

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LeetCode 2781 - Length of the Longest Valid Substring

LeetCode Problem 2781 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Sliding Window Solution LeetCode 2781 - Length of the Longest Valid Substring Problem Understanding The problem gives us a string word and a list of forbidden strings forbidden . A substring is considered valid if none of its internal substrings appear in the forbidden list. In other words, for a candidate substring word[l:r] , every contiguous segment inside it...

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LeetCode 2838 - Maximum Coins Heroes Can Collect

LeetCode Problem 2838 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting, Prefix Sum Solution LeetCode 2838 - Maximum Coins Heroes Can Collect Problem Understanding This problem gives us three arrays: heroes , where heroes[i] represents the power of the i th hero. monsters , where monsters[j] represents the power of the j th monster. coins , where coins[j] represents the reward obtained for defeating the j th monster....

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LeetCode 2770 - Maximum Number of Jumps to Reach the Last Index

LeetCode Problem 2770 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to determine the maximum number of jumps one can make from the first element of an array nums to the last element, subject to a jumping constraint. Each jump from index i to index j must satisfy two conditions: i < j and the difference between the values at these indices, nums[j] -...

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LeetCode 2748 - Number of Beautiful Pairs

LeetCode Problem 2748 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Counting, Number Theory Solution LeetCode 2748 - Number of Beautiful Pairs Problem Understanding The problem gives us a 0-indexed integer array nums . We must count how many pairs of indices (i, j) satisfy 0 <= i < j < n and have the following property: Take the first digit of nums[i] . Take the last digit of nums[j]...

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LeetCode 3245 - Alternating Groups III

LeetCode Problem 3245 Difficulty: 🔴 Hard Topics: Array, Binary Indexed Tree, Ordered Set Solution Problem Understanding We are given a circular array called colors , where each element is either 0 or 1 . These represent red and blue tiles arranged in a ring, which means index 0 and index n - 1 are adjacent. A group is considered alternating if every adjacent pair inside that contiguous segment has different...

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LeetCode 3145 - Find Products of Elements of Big Array

LeetCode Problem 3145 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation Solution Problem Understanding The problem asks us to work with a conceptual infinite array called big_nums , which is generated by taking every positive integer i , converting it to its powerful array (the sorted array of powers of two that sum to i ), and concatenating all these arrays sequentially. For instance, 1 → [1] , 2...

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LeetCode 2702 - Minimum Operations to Make Numbers Non-positive

LeetCode Problem 2702 Difficulty: 🔴 Hard Topics: Array, Binary Search Solution Problem Understanding In this problem, we are given an array nums and two integers x and y , where x > y . During each operation, we choose one index i and apply two different decrements: nums[i] decreases by x every other element decreases by y The goal is to determine the minimum number of operations needed so that...

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LeetCode 2874 - Maximum Value of an Ordered Triplet II

LeetCode Problem 2874 Difficulty: 🟡 Medium Topics: Array Solution LeetCode 2874 - Maximum Value of an Ordered Triplet II Problem Understanding The problem gives us a 0-indexed integer array nums and asks us to find the maximum possible value of: $$(nums[i] - nums[j]) \times nums[k]$$ subject to the constraint: $$i < j < k$$ In other words, we must choose three indices in increasing order. The first element contributes positively,...

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LeetCode 3105 - Longest Strictly Increasing or Strictly Decreasing Subarray

LeetCode Problem 3105 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 3105, Longest Strictly Increasing or Strictly Decreasing Subarray Problem Understanding The problem gives us an integer array nums and asks us to find the length of the longest contiguous subarray that is either strictly increasing or strictly decreasing. A subarray must consist of consecutive elements from the original array. This is important because we cannot skip elements. For example, in...

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LeetCode 2784 - Check if Array is Good

LeetCode Problem 2784 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting Solution Problem Understanding The problem defines a special type of array called a "good" array. A good array must be a permutation of: $$base[n] = [1, 2, 3, ..., n-1, n, n]$$ This means the array must contain: Every integer from 1 to n - 1 exactly once The integer n exactly twice No other numbers Total length equal...

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LeetCode 2439 - Minimize Maximum of Array

LeetCode Problem 2439 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Greedy, Prefix Sum Solution Problem Understanding The problem gives a 0-indexed array nums of non-negative integers and allows a specific operation: choose an index i (where 1 <= i < n ) such that nums[i] > 0 , then decrease nums[i] by 1 and increase nums[i - 1] by 1. The task is to perform this operation any...

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LeetCode 3071 - Minimum Operations to Write the Letter Y on a Grid

LeetCode Problem 3071 Difficulty: 🟡 Medium Topics: Array, Hash Table, Matrix, Counting Solution Problem Understanding The problem asks us to determine the minimum number of operations to convert a given n x n grid into a representation of the letter Y, under specific conditions. The grid contains integers 0, 1, or 2. The cells that belong to the Y consist of two diagonals starting from the top corners to the...

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LeetCode 2717 - Semi-Ordered Permutation

LeetCode Problem 2717 Difficulty: 🟢 Easy Topics: Array, Simulation Solution LeetCode 2717 - Semi-Ordered Permutation Problem Understanding The problem gives us a permutation nums of length n . A permutation means the array contains every integer from 1 to n exactly once. A permutation is considered semi-ordered when: The first element is 1 The last element is n We are allowed to repeatedly swap adjacent elements. Each adjacent swap counts...

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LeetCode 2612 - Minimum Reverse Operations

LeetCode Problem 2612 Difficulty: 🔴 Hard Topics: Array, Hash Table, Breadth-First Search, Union-Find, Ordered Set Solution This will be a very large, multi-thousand-word technical guide because of the required depth, full proofs, worked examples, Python and Go implementations, detailed walkthroughs, complexity reasoning, and exhaustive tests. To ensure quality and avoid truncation, I will split it cleanly into sections across messages. Part 1: Problem Understanding, Approaches, Algorithm Walkthrough, and Python Solution...

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LeetCode 2926 - Maximum Balanced Subsequence Sum

LeetCode Problem 2926 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Binary Indexed Tree, Segment Tree Solution Problem Understanding This problem asks us to find the maximum sum of a balanced subsequence from a given integer array nums . A subsequence is a selection of elements from the array in their original order, possibly skipping elements. A subsequence is balanced if, for every pair of consecutive indices i and...

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LeetCode 2239 - Find Closest Number to Zero

LeetCode Problem 2239 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us an integer array nums , and we need to return the number whose value is closest to 0 . The phrase "closest to zero" means we compare numbers using their absolute values. For example: |-2| = 2 |5| = 5 Since 2 < 5 , the number -2 is closer to zero than 5 ....

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LeetCode 2352 - Equal Row and Column Pairs

LeetCode Problem 2352 Difficulty: 🟡 Medium Topics: Array, Hash Table, Matrix, Simulation Solution Problem Understanding The problem gives us a square matrix grid of size n x n , where every element is an integer. We need to count how many (row, column) pairs are exactly equal. More specifically, for every row ri and every column cj , we compare the sequence of elements in that row with the sequence...

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LeetCode 1981 - Minimize the Difference Between Target and Chosen Elements

LeetCode Problem 1981 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to select exactly one element from each row of a given m x n integer matrix mat such that the sum of the selected elements is as close as possible to a given integer target . The goal is to minimize the absolute difference between the sum of chosen elements and the...

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LeetCode 2857 - Count Pairs of Points With Distance k

LeetCode Problem 2857 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation Solution LeetCode 2857 - Count Pairs of Points With Distance k Problem Understanding We are given a list of 2D points, where each point is represented as [x, y] , and an integer k . The distance between two points is not the usual Euclidean or Manhattan distance. Instead, it is defined as: $$(x_1 \oplus x_2) + (y_1...

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LeetCode 2210 - Count Hills and Valleys in an Array

LeetCode Problem 2210 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to identify hills and valleys in an integer array nums . A hill is a position where the closest non-equal neighbors on both sides are smaller than the current value, and a valley is where those neighbors are larger. Consecutive elements with the same value are considered part of the same hill or valley, so...

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LeetCode 2974 - Minimum Number Game

LeetCode Problem 2974 Difficulty: 🟢 Easy Topics: Array, Sorting, Heap (Priority Queue), Simulation Solution Problem Understanding The problem gives us an integer array nums with an even number of elements. We repeatedly simulate a game between Alice and Bob until the array becomes empty. In each round, the following sequence happens: Alice removes the smallest remaining number. Bob removes the next smallest remaining number. Bob appends his removed number to...

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LeetCode 3147 - Taking Maximum Energy From the Mystic Dungeon

LeetCode Problem 3147 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem asks us to maximize the total energy gained from a sequence of magicians arranged in a line, where each magician provides a certain energy value, which can be negative or positive. The catch is that after taking energy from a magician at index i , you are instantly teleported to magician (i +...

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LeetCode 2617 - Minimum Number of Visited Cells in a Grid

LeetCode Problem 2617 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Stack, Breadth-First Search, Union-Find, Heap (Priority Queue), Matrix, Monotonic Stack Solution Problem Understanding The problem asks us to determine the minimum number of cells we need to visit in order to reach the bottom-right corner of a given m x n grid. Each cell (i, j) contains a number grid[i][j] representing the maximum number of steps we can move right...

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LeetCode 3076 - Shortest Uncommon Substring in an Array

LeetCode Problem 3076 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Trie Solution Problem Understanding The problem asks us to find, for each string in a given array, the shortest substring that does not appear in any other string in the array. If multiple shortest substrings exist, we must choose the lexicographically smallest one. If no such substring exists, the answer for that string is an empty string. In other...

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LeetCode 3391 - Design a 3D Binary Matrix with Efficient Layer Tracking

LeetCode Problem 3391 Difficulty: 🟡 Medium Topics: Array, Hash Table, Design, Heap (Priority Queue), Matrix, Ordered Set Solution Problem Understanding The problem asks us to design a data structure that manages a 3D binary matrix of size n x n x n . Every cell initially contains 0 , and we must support three operations efficiently: setCell(x, y, z) sets a specific cell to 1 . unsetCell(x, y, z) sets...

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LeetCode 2354 - Number of Excellent Pairs

LeetCode Problem 2354 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Bit Manipulation Solution Problem Understanding The problem provides a 0-indexed array of positive integers nums and a positive integer k . The task is to count all distinct pairs (num1, num2) such that both numbers exist in nums and the sum of the number of set bits in num1 OR num2 and num1 AND num2 is at least...

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LeetCode 2602 - Minimum Operations to Make All Array Elements Equal

LeetCode Problem 2602 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sorting, Prefix Sum Solution Problem Understanding The problem gives us an integer array nums and another array queries . For every query value q , we must calculate the minimum number of operations required to make every element in nums equal to q . One operation consists of increasing or decreasing a single element by exactly 1 . Since each...

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LeetCode 3047 - Find the Largest Area of Square Inside Two Rectangles

LeetCode Problem 3047 Difficulty: 🟡 Medium Topics: Array, Math, Geometry Solution Problem Understanding The problem asks us to find the largest square that can fit inside the overlapping region of at least two rectangles on a 2D plane. Each rectangle is axis-aligned, meaning its sides are parallel to the x-axis and y-axis. The rectangles are defined by their bottom-left and top-right coordinates, which are given as integer pairs in two...

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LeetCode 1912 - Design Movie Rental System

LeetCode Problem 1912 Difficulty: 🔴 Hard Topics: Array, Hash Table, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem requires designing a movie rental system for multiple shops, where each shop carries at most one copy of each movie. We are asked to implement a class that efficiently supports searching for available movies, renting them, returning them, and reporting the cheapest currently rented movies. The input consists of...

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LeetCode 3027 - Find the Number of Ways to Place People II

LeetCode Problem 3027 Difficulty: 🔴 Hard Topics: Array, Math, Geometry, Sorting, Enumeration Solution Problem Understanding The problem asks us to determine how many valid placements of Alice and Bob exist on a 2D grid of points such that Alice can build a rectangular fence with her position as the upper left corner and Bob’s position as the lower right corner . A placement is only valid if no other person...

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LeetCode 3143 - Maximum Points Inside the Square

LeetCode Problem 3143 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Binary Search, Sorting Solution Problem Understanding The problem asks us to find the maximum number of points that can be contained in a square centered at the origin (0, 0) such that no two points inside the square share the same tag. The square's edges are parallel to the axes, and points on the edges are considered inside. The...

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LeetCode 3287 - Find the Maximum Sequence Value of Array

LeetCode Problem 3287 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution LeetCode 3287 - Find the Maximum Sequence Value of Array Problem Understanding We are given an array nums and an integer k . We must choose a subsequence of exactly 2 * k elements while preserving the original order of the array. After selecting the subsequence, we split it into two equal halves: The first k selected...

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LeetCode 2747 - Count Zero Request Servers

LeetCode Problem 2747 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window, Sorting Solution Problem Understanding This problem asks us to count servers that did not receive any requests within a certain time window for multiple queries. You are given n servers, each with a unique ID from 1 to n . The logs array records requests, where each entry [server_id, time] indicates that server_id received a request at time...

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LeetCode 3122 - Minimum Number of Operations to Satisfy Conditions

LeetCode Problem 3122 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding The problem presents a two-dimensional matrix grid of size m x n with integer values in the range 0 to 9. The task is to transform this matrix using the minimum number of operations, where each operation allows you to change the value of any cell to any non-negative integer. After all operations, the matrix must...

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LeetCode 2152 - Minimum Number of Lines to Cover Points

LeetCode Problem 2152 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Dynamic Programming, Backtracking, Bit Manipulation, Geometry, Bitmask Solution Problem Understanding This problem asks us to determine the minimum number of straight lines needed to cover a given set of points on an X-Y plane. Each point is defined by its (x, y) coordinates, and a straight line can pass through any number of points as long as they are...

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LeetCode 1955 - Count Number of Special Subsequences

LeetCode Problem 1955 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding This problem asks us to count the number of special subsequences in an array nums that consists only of integers 0 , 1 , and 2 . A subsequence is special if it follows the pattern of one or more 0 s, followed by one or more 1 s, followed by one or more 2 s ....

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LeetCode 3217 - Delete Nodes From Linked List Present in Array

LeetCode Problem 3217 Difficulty: 🟡 Medium Topics: Array, Hash Table, Linked List Solution Problem Understanding This problem asks us to modify a singly linked list by removing all nodes whose values appear in a given array nums . The input consists of two elements: an array of integers nums and the head of a linked list. Each node in the linked list contains an integer value and a pointer to...

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LeetCode 2107 - Number of Unique Flavors After Sharing K Candies

LeetCode Problem 2107 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution LeetCode 2107 - Number of Unique Flavors After Sharing K Candies Problem Understanding The problem gives us an integer array candies , where each value represents the flavor of a candy. We must give exactly k consecutive candies to our sister. After removing those k candies, we keep the remaining candies for ourselves. Our goal is to...

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LeetCode 2568 - Minimum Impossible OR

LeetCode Problem 2568 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Brainteaser Solution Problem Understanding The problem asks us to find the smallest positive integer that cannot be represented as a bitwise OR of any subsequence of a given array nums . The input array contains positive integers, and the subsequences can have any length, including length 1. The output must be the smallest integer greater than zero that cannot be...

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LeetCode 2221 - Find Triangular Sum of an Array

LeetCode Problem 2221 Difficulty: 🟡 Medium Topics: Array, Math, Simulation, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to compute the triangular sum of an array of digits. The triangular sum is obtained by repeatedly reducing the array according to a simple rule: for every pair of adjacent elements, sum them modulo 10 to form a new array of length one less than the current array. This reduction...

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LeetCode 3356 - Zero Array Transformation II

LeetCode Problem 3356 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Prefix Sum Solution Problem Understanding The problem asks us to determine the minimum number of sequential queries required to transform an array nums into a Zero Array , where all elements are zero. Each query specifies a subarray [li, ri] and a value vali . We are allowed to decrement each element within that subarray by any value...

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LeetCode 3359 - Find Sorted Submatrices With Maximum Element at Most K

LeetCode Problem 3359 Difficulty: 🔴 Hard Topics: Array, Stack, Matrix, Monotonic Stack Solution Problem Understanding We are given a matrix grid with m rows and n columns, along with an integer k . The task is to count how many rectangular submatrices satisfy two conditions simultaneously: Every value inside the submatrix must be at most k . Every row inside the submatrix must be sorted in non-increasing order from left...

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LeetCode 2586 - Count the Number of Vowel Strings in Range

LeetCode Problem 2586 Difficulty: 🟢 Easy Topics: Array, String, Counting Solution Problem Understanding The problem gives us an array of lowercase strings called words and two integer indices, left and right . We need to count how many strings within the inclusive range [left, right] are considered vowel strings. A string qualifies as a vowel string if both of these conditions are true: The first character is a vowel. The...

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LeetCode 2099 - Find Subsequence of Length K With the Largest Sum

LeetCode Problem 2099 Difficulty: 🟢 Easy Topics: Array, Hash Table, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem asks us to find a subsequence of length k from a given integer array nums such that the sum of the elements in the subsequence is maximized. A subsequence is defined as a sequence that can be obtained from the original array by deleting zero or more elements without changing the...

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LeetCode 2639 - Find the Width of Columns of a Grid

LeetCode Problem 2639 Difficulty: 🟢 Easy Topics: Array, Matrix Solution Problem Understanding The problem gives us a two dimensional integer matrix called grid with m rows and n columns. Our task is to compute the width of every column independently. The width of a column is defined as the maximum string length among all integers appearing in that column. The length calculation follows standard integer string formatting rules: Positive numbers...

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LeetCode 1984 - Minimum Difference Between Highest and Lowest of K Scores

LeetCode Problem 1984 Difficulty: 🟢 Easy Topics: Array, Sliding Window, Sorting Solution Problem Understanding The problem asks us to find the minimum possible difference between the highest and lowest scores when selecting exactly k scores from an array of student scores. The input is a 0-indexed integer array nums where each element represents a student's score, and an integer k which is the number of scores to pick. The expected...

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LeetCode 1928 - Minimum Cost to Reach Destination in Time

LeetCode Problem 1928 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Graph Theory Solution Problem Understanding The problem asks us to find the minimum cost to travel from city 0 to city n-1 within a given time limit, maxTime , where the cost is defined by passing fees associated with each city visited. The country has n cities connected by bi-directional roads with varying travel times. Multiple roads may exist between...

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LeetCode 2137 - Pour Water Between Buckets to Make Water Levels Equal

LeetCode Problem 2137 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding This problem asks us to equalize the water levels in a series of buckets while accounting for a spill loss. Each bucket initially contains some quantity of water given in an array buckets , and every time we pour water from one bucket to another, a percentage of that water, loss , is lost. The goal is...

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LeetCode 2411 - Smallest Subarrays With Maximum Bitwise OR

LeetCode Problem 2411 Difficulty: 🟡 Medium Topics: Array, Binary Search, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to find, for each index in a given array nums , the length of the shortest contiguous subarray starting at that index whose bitwise OR is equal to the maximum possible bitwise OR obtainable from that index onward . In other words, we need to look at all subarrays...

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LeetCode 2398 - Maximum Number of Robots Within Budget

LeetCode Problem 2398 Difficulty: 🔴 Hard Topics: Array, Binary Search, Queue, Sliding Window, Heap (Priority Queue), Prefix Sum, Monotonic Queue Solution Problem Understanding This problem asks us to determine the maximum number of consecutive robots that can be run without exceeding a given budget. We are given two arrays of length n : chargeTimes and runningCosts . For any consecutive subset of k robots, the total cost is computed as:...

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LeetCode 2237 - Count Positions on Street With Required Brightness

LeetCode Problem 2237 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem describes a street represented by positions from 0 to n - 1 . There are multiple street lamps, each defined by its position and range. A lamp at position p with range r illuminates all positions from max(0, p - r) to min(n - 1, p + r) , inclusive. The brightness of a position...

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LeetCode 2353 - Design a Food Rating System

LeetCode Problem 2353 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Design, Heap (Priority Queue), Ordered Set Solution Problem Understanding The problem is asking us to implement a food rating system that supports dynamic updates to the ratings of individual food items and allows querying for the highest-rated food for a given cuisine. Each food has a unique name, belongs to exactly one cuisine, and has an associated rating. The...

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LeetCode 1998 - GCD Sort of an Array

LeetCode Problem 1998 Difficulty: 🔴 Hard Topics: Array, Math, Union-Find, Sorting, Number Theory Solution Problem Understanding The problem asks whether it is possible to sort an integer array nums into non-decreasing order using a very specific type of swap. You can swap any two elements nums[i] and nums[j] if and only if their greatest common divisor (GCD) is greater than 1. The input is an array of integers ranging from...

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LeetCode 2453 - Destroy Sequential Targets

LeetCode Problem 2453 Difficulty: 🟡 Medium Topics: Array, Hash Table, Counting Solution Problem Understanding The problem presents a scenario where we have a list of positive integers nums representing targets placed on a number line. We also have an integer space representing the step interval of a machine. The machine can destroy all targets starting from an initial seed value nums[i] in steps of space . In other words, if...

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LeetCode 2369 - Check if There is a Valid Partition For The Array

LeetCode Problem 2369 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution LeetCode 2369 - Check if There is a Valid Partition Problem Understanding The problem gives us an integer array nums , and we must determine whether it is possible to split the array into contiguous groups such that every group satisfies one of three valid patterns. A valid group can be: Exactly two equal numbers, such as [5,5] Exactly...

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LeetCode 3363 - Find the Maximum Number of Fruits Collected

LeetCode Problem 3363 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Matrix Solution Problem Understanding This problem asks us to maximize the total number of fruits collected by three children traversing a square grid of rooms, each with a certain number of fruits. The grid has dimensions n x n , and the fruits are given in a 2D array fruits[i][j] . The three children start at fixed corners: (0,0) ,...

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LeetCode 3385 - Minimum Time to Break Locks II

LeetCode Problem 3385 Difficulty: 🔴 Hard Topics: Array, Breadth-First Search, Graph Theory Solution Problem Understanding In this problem, Bob must break a collection of locks, where each lock requires a certain minimum amount of energy before it can be destroyed. The input array strength represents these requirements. If strength[i] = s , then Bob must wait until the sword's energy reaches at least s before breaking that lock. The sword...

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LeetCode 2931 - Maximum Spending After Buying Items

LeetCode Problem 2931 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting, Heap (Priority Queue), Matrix Solution LeetCode 2931 - Maximum Spending After Buying Items Problem Understanding We are given an m × n matrix values where each row represents a shop and each column represents an item in that shop. The important property is that every row is sorted in non-increasing order: values[i][0] >= values[i][1] >= ... >= values[i][n-1] When buying...

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LeetCode 2587 - Rearrange Array to Maximize Prefix Score

LeetCode Problem 2587 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Prefix Sum Solution Problem Understanding The problem gives us a 0-indexed array of integers , nums , which can include negative numbers, zero, and positive numbers. We are allowed to reorder the elements in any way we choose. After reordering, we compute the prefix sum array , prefix , where prefix[i] is the sum of all elements from index 0...

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LeetCode 2256 - Minimum Average Difference

LeetCode Problem 2256 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding In this problem, we are given a 0-indexed integer array nums , and for every index i , we must compute something called the "average difference". For a particular index i , the array is split into two parts: The left part contains elements from index 0 through i The right part contains elements from index i...

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LeetCode 2958 - Length of Longest Subarray With at Most K Frequency

LeetCode Problem 2958 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sliding Window Solution Problem Understanding The problem asks us to find the length of the longest contiguous subarray in an array of integers nums such that the frequency of every element in that subarray does not exceed a given integer k . In other words, in the resulting subarray, no number appears more than k times. The input consists of...

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LeetCode 3213 - Construct String with Minimum Cost

LeetCode Problem 3213 Difficulty: 🔴 Hard Topics: Array, String, Dynamic Programming, Suffix Array Solution Problem Understanding The problem asks us to construct a target string target by repeatedly appending strings from a given array words , where each word has an associated cost in costs . The goal is to determine the minimum total cost to construct target exactly. If it is impossible to form target from the given words,...

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LeetCode 3219 - Minimum Cost for Cutting Cake II

LeetCode Problem 3219 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding We are given an m x n rectangular cake and need to divide it completely into 1 x 1 pieces. The cake can be cut along predefined horizontal and vertical lines. There are m - 1 possible horizontal cuts and n - 1 possible vertical cuts: horizontalCut[i] is the cost of cutting across horizontal line i verticalCut[j]...

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LeetCode 3012 - Minimize Length of Array Using Operations

LeetCode Problem 3012 Difficulty: 🟡 Medium Topics: Array, Math, Greedy, Number Theory Solution Problem Understanding The problem gives us a 0-indexed array of positive integers and asks us to repeatedly perform a specific operation to reduce the array's length as much as possible. The operation involves selecting two distinct indices i and j with positive numbers, inserting nums[i] % nums[j] at the end, and removing the original two elements. The...

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LeetCode 2079 - Watering Plants

LeetCode Problem 2079 Difficulty: 🟡 Medium Topics: Array, Simulation Solution Problem Understanding This problem asks us to simulate watering a row of plants with a watering can that has a fixed capacity. The plants are arranged along a straight line with indices representing their positions. You start at a river located at position x = -1 where you can refill your watering can. Each plant requires a specific amount of...

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LeetCode 2818 - Apply Operations to Maximize Score

LeetCode Problem 2818 Difficulty: 🔴 Hard Topics: Array, Math, Stack, Greedy, Sorting, Monotonic Stack, Number Theory Solution Problem Understanding The problem gives us an array nums and an integer k . We begin with a score of 1 , and we are allowed to perform at most k operations. In each operation, we choose a subarray that has not been chosen before. From that subarray, we select the element with...

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LeetCode 2078 - Two Furthest Houses With Different Colors

LeetCode Problem 2078 Difficulty: 🟢 Easy Topics: Array, Greedy Solution Problem Understanding The problem is asking us to find the maximum distance between two houses that have different colors . You are given a 0-indexed list colors where each element represents the color of a house. The distance between two houses at indices i and j is defined as abs(i - j) - the absolute difference of their indices. The...

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LeetCode 2399 - Check Distances Between Same Letters

LeetCode Problem 2399 Difficulty: 🟢 Easy Topics: Array, Hash Table, String Solution Problem Understanding This problem asks us to verify whether a string follows a very specific spacing rule between repeated characters. We are given a string s that contains only lowercase English letters. Every character that appears in the string appears exactly twice. We are also given an integer array distance of size 26 , where each index corresponds...

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LeetCode 2647 - Color the Triangle Red

LeetCode Problem 2647 Difficulty: 🔴 Hard Topics: Array, Math Solution Problem Understanding The problem asks us to determine the minimal set of initial triangles to color red in an equilateral triangle of side length n , such that by repeatedly applying a propagation rule, all triangles eventually become red. The propagation rule is simple: any white triangle with at least two red neighbors becomes red automatically. The input n specifies...

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LeetCode 3398 - Smallest Substring With Identical Characters I

LeetCode Problem 3398 Difficulty: 🔴 Hard Topics: Array, Binary Search, Enumeration Solution Problem Understanding The problem gives us a binary string s consisting of only '0' and '1' characters and an integer numOps representing the maximum number of bit flips we can perform. The objective is to minimize the length of the longest contiguous substring where all characters are identical after performing at most numOps flips. In simpler terms, we...

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LeetCode 2242 - Maximum Score of a Node Sequence

LeetCode Problem 2242 Difficulty: 🔴 Hard Topics: Array, Graph Theory, Sorting, Enumeration Solution Problem Understanding The problem gives us an undirected graph with n nodes. Each node has a score, and the graph edges define which nodes are directly connected. We must find a valid sequence of exactly four distinct nodes such that every adjacent pair in the sequence has an edge between them. A valid sequence looks like this:...

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LeetCode 3205 - Maximum Array Hopping Score I

LeetCode Problem 3205 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Stack, Greedy, Monotonic Stack Solution Problem Understanding The problem asks us to calculate the maximum score achievable by hopping through an array from the first element to the last. You start at index 0 , and at each step, you can jump to any subsequent index j > i . When you jump, you accumulate a score of (j -...

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LeetCode 2306 - Naming a Company

LeetCode Problem 2306 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Bit Manipulation, Enumeration Solution Problem Understanding The problem gives us a list of unique strings called ideas . We must repeatedly choose two different strings, swap their first characters, and determine whether the newly formed strings are both absent from the original list. If both newly generated names do not already exist in ideas , then the ordered pair...

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LeetCode 2111 - Minimum Operations to Make the Array K-Increasing

LeetCode Problem 2111 Difficulty: 🔴 Hard Topics: Array, Binary Search Solution Problem Understanding The problem asks us to transform a given array arr into a K-increasing array using the minimum number of operations. A K-increasing array is defined such that for every index i where i >= k , the condition arr[i-k] <= arr[i] holds. Each operation allows us to pick any index i and change arr[i] to any positive...

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LeetCode 2528 - Maximize the Minimum Powered City

LeetCode Problem 2528 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Queue, Sliding Window, Prefix Sum Solution Problem Understanding The problem asks us to determine the maximum possible minimum power that any city can have after optimally adding k new power stations to an existing configuration. Each city already has some power stations, and each station has a range r over which it contributes to the power of nearby cities....

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LeetCode 3199 - Count Triplets with Even XOR Set Bits I

LeetCode Problem 3199 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us three integer arrays, a , b , and c . We must count how many triplets (a[i], b[j], c[k]) produce a bitwise XOR result with an even number of set bits. A set bit is a bit equal to 1 in the binary representation of a number. For example: 5 in binary is...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1878 - Get Biggest Three Rhombus Sums in a Grid

LeetCode Problem 1878 Difficulty: 🟡 Medium Topics: Array, Math, Sorting, Heap (Priority Queue), Matrix, Prefix Sum Solution Problem Understanding The problem asks us to compute the largest three distinct rhombus sums in a given m x n integer grid. A rhombus in this context is a square rotated 45 degrees, whose corners align with grid cells. The rhombus sum includes only the border cells of this shape, not the interior....

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LeetCode 1862 - Sum of Floored Pairs

LeetCode Problem 1862 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Counting, Enumeration, Prefix Sum Solution Problem Understanding The problem asks us to calculate the sum of the integer division results, floor(nums[i] / nums[j]) , for every pair of elements (i, j) in a given array nums . Here, floor() represents the largest integer less than or equal to the division result. The array nums can have up to 10^5...

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LeetCode 2333 - Minimum Sum of Squared Difference

LeetCode Problem 2333 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting, Heap (Priority Queue) Solution I can do that, but the complete guide with all requested sections and the level of detail you specified will exceed a single message limit. I will split it cleanly into multiple parts while preserving your exact formatting requirements. Planned structure: Part 1 Problem Understanding Approaches Algorithm Walkthrough Why the greedy + binary search...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1882 - Process Tasks Using Servers

LeetCode Problem 1882 Difficulty: 🟡 Medium Topics: Array, Heap (Priority Queue) Solution Problem Understanding This problem asks us to simulate a task scheduling system with two priority rules. We are given a list of servers and a list of tasks. Each server has a weight, and each task has a processing duration. At second j , task j becomes available and enters a queue. Tasks must always be assigned in...

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3072 - Distribute Elements Into Two Arrays II

LeetCode Problem 3072 Difficulty: 🔴 Hard Topics: Array, Binary Indexed Tree, Segment Tree, Simulation Solution Problem Understanding This problem requires simulating the distribution of elements from a 1-indexed array nums into two separate arrays arr1 and arr2 under specific rules. Each element in nums is assigned sequentially to one of the arrays according to a comparison of how many elements in each array are strictly greater than the current element....

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LeetCode 2164 - Sort Even and Odd Indices Independently

LeetCode Problem 2164 Difficulty: 🟢 Easy Topics: Array, Sorting Solution Problem Understanding The problem asks us to take an integer array nums and sort its elements based on their indices in two separate ways: the elements at even indices should be sorted in non-decreasing order, and the elements at odd indices should be sorted in non-increasing order. The array is 0-indexed , so index 0 is considered even, index 1...

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LeetCode 2448 - Minimum Cost to Make Array Equal

LeetCode Problem 2448 Difficulty: 🔴 Hard Topics: Array, Binary Search, Greedy, Sorting, Prefix Sum Solution This guide will use the weighted median optimization approach, which is the key insight behind solving this problem efficiently within the constraints. Problem Understanding The problem gives us two arrays, nums and cost , each of length n . The nums[i] value represents the current number at index i , and cost[i] represents how expensive...

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LeetCode 3251 - Find the Count of Monotonic Pairs II

LeetCode Problem 3251 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Combinatorics, Prefix Sum Solution Problem Understanding The problem asks us to count the number of ways we can split an array of positive integers, nums , into two arrays, arr1 and arr2 , such that they satisfy a set of monotonic conditions. Specifically, arr1 must be non-decreasing, arr2 must be non-increasing, and for each index i , their sum...

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LeetCode 3160 - Find the Number of Distinct Colors Among the Balls

LeetCode Problem 3160 Difficulty: 🟡 Medium Topics: Array, Hash Table, Simulation Solution Problem Understanding The problem gives us limit + 1 balls labeled from 0 to limit . Initially, none of the balls have a color assigned. We then process a sequence of queries, where each query is of the form [x, y] . This means ball x should now be painted with color y . The important detail is...

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LeetCode 3238 - Find the Number of Winning Players

LeetCode Problem 3238 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution LeetCode 3238 - Find the Number of Winning Players Problem Understanding The problem gives us n players and a list called pick , where each entry is of the form [xi, yi] . This means player xi picked a ball with color yi . A player wins if they have picked strictly more than their player index number...

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LeetCode 3240 - Minimum Number of Flips to Make Binary Grid Palindromic II

LeetCode Problem 3240 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Matrix Solution Problem Understanding We are given a binary matrix grid with m rows and n columns. Every cell contains either 0 or 1 . We may flip any cell, meaning we can change 0 to 1 or 1 to 0 . The goal is to perform the minimum number of flips such that two conditions become true simultaneously: Every...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1944 - Number of Visible People in a Queue

LeetCode Problem 1944 Difficulty: 🔴 Hard Topics: Array, Stack, Monotonic Stack Solution Problem Understanding The problem gives a queue of n people standing from left to right, where each person has a distinct height. For each person i , we need to determine how many people to their right they can see. A person i can see a person j (with j > i ) if every person between them...

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LeetCode 2482 - Difference Between Ones and Zeros in Row and Column

LeetCode Problem 2482 Difficulty: 🟡 Medium Topics: Array, Matrix, Simulation Solution LeetCode 2482 - Difference Between Ones and Zeros in Row and Column Problem Understanding The problem gives us a binary matrix grid with m rows and n columns. Every cell contains either 0 or 1 . We must construct another matrix called diff , where each position diff[i][j] depends on how many ones and zeros appear in row i...

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LeetCode 3116 - Kth Smallest Amount With Single Denomination Combination

LeetCode Problem 3116 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Bit Manipulation, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to determine the kth smallest amount that can be formed using coins of given denominations under a strict limitation: we can only use a single type of coin at a time . In other words, combinations of different denominations are not allowed . The input consists of...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2570 - Merge Two 2D Arrays by Summing Values

LeetCode Problem 2570 Difficulty: 🟢 Easy Topics: Array, Hash Table, Two Pointers Solution Problem Understanding The problem gives us two sorted 2D integer arrays, nums1 and nums2 , where every element is a pair of integers in the form [id, value] . Each id uniquely identifies an entry inside its own array, and the corresponding value represents that id's associated number. Since both arrays are already sorted in ascending order...

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LeetCode 1994 - The Number of Good Subsets

LeetCode Problem 1994 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Bit Manipulation, Counting, Number Theory, Bitmask Solution LeetCode 1994 - The Number of Good Subsets Problem Understanding This problem asks us to count how many subsets of the input array have a product that can be written as a multiplication of distinct prime numbers. The phrase "distinct prime numbers" is the key restriction. A product is valid...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1908 - Game of Nim

LeetCode Problem 1908 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Bit Manipulation, Brainteaser, Game Theory Solution Problem Understanding This problem is the classic mathematical game known as Nim. We are given an array piles , where each element represents the number of stones in a pile. Two players, Alice and Bob, take turns removing stones. On each turn, a player may choose any non-empty pile and remove any positive...

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LeetCode 3018 - Maximum Number of Removal Queries That Can Be Processed I

LeetCode Problem 3018 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to process a sequence of removal queries on an array nums , with an optional initial operation where we can replace nums with any subsequence of itself to optimize query processing. Each query specifies a threshold value. At each query, if either the first or last element of nums is greater than or...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1872 - Stone Game VIII

LeetCode Problem 1872 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Prefix Sum, Game Theory Solution Problem Understanding The problem describes a two-player turn-based game between Alice and Bob with a row of stones, each having an integer value. The key rules are that on a turn, a player removes more than one stone from the left , sums their values to their score, and then places a new stone...

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LeetCode 1894 - Find the Student that Will Replace the Chalk

LeetCode Problem 1894 Difficulty: 🟡 Medium Topics: Array, Binary Search, Simulation, Prefix Sum Solution Problem Understanding The problem presents a classroom scenario where students are given problems in a round-robin order, consuming a certain number of chalk pieces for each problem. We are given an array chalk , where chalk[i] indicates the number of chalk pieces student i uses, and an integer k representing the initial chalk supply. Starting from...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2706 - Buy Two Chocolates

LeetCode Problem 2706 Difficulty: 🟢 Easy Topics: Array, Greedy, Sorting Solution Problem Understanding The problem is asking us to purchase exactly two chocolates from a store given their individual prices, while ensuring that after buying them we do not end up in debt. The input consists of an array prices , where each element represents the cost of one chocolate, and an integer money , which is the total money...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3277 - Maximum XOR Score Subarray Queries

LeetCode Problem 3277 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem gives us an integer array nums and several range queries. For each query [li, ri] , we must examine every possible subarray fully contained inside nums[li..ri] and return the maximum XOR score among them. The unusual part of the problem is the definition of the XOR score. Instead of simply XORing all elements directly, the...

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LeetCode 2772 - Apply Operations to Make All Array Elements Equal to Zero

LeetCode Problem 2772 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem gives us an integer array nums and an integer k . We are allowed to repeatedly choose any contiguous subarray of length k and decrease every element inside that subarray by 1 . Our goal is to determine whether it is possible to make every element in the array equal to 0 after performing any...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1870 - Minimum Speed to Arrive on Time

LeetCode Problem 1870 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution Problem Understanding The problem asks us to find the minimum constant speed (in kilometers per hour) required to travel a sequence of train rides and reach the destination within a given floating-point hour . Each train has a fixed distance, and each subsequent train can only depart at the next integer hour. This waiting period after each ride creates...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2433 - Find The Original Array of Prefix Xor

LeetCode Problem 2433 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem is asking us to reverse-engineer an array arr from its prefix XOR array pref . Specifically, pref[i] represents the XOR of all elements in arr from index 0 to i . Our goal is to reconstruct arr given only pref . For instance, if pref = [5,2,0,3,1] , it means: pref[0] = arr[0] pref[1] =...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2191 - Sort the Jumbled Numbers

LeetCode Problem 2191 Difficulty: 🟡 Medium Topics: Array, Sorting Solution Problem Understanding The problem asks us to sort an array of integers based on a custom digit mapping rather than their natural numeric value. Each digit from 0 to 9 has a mapped value given in the mapping array, and every number in nums can be "transformed" by replacing each digit according to this mapping. The key point is that...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2856 - Minimum Array Length After Pair Removals

LeetCode Problem 2856 Difficulty: 🟡 Medium Topics: Array, Hash Table, Two Pointers, Binary Search, Greedy, Counting Solution Problem Understanding This problem gives us a sorted integer array nums in non-decreasing order. We may repeatedly remove pairs of elements under one important rule: for a chosen pair (i, j) , the values must satisfy nums[i] < nums[j] . In other words, the two chosen numbers cannot be equal, and the smaller...

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LeetCode 3115 - Maximum Prime Difference

LeetCode Problem 3115 Difficulty: 🟡 Medium Topics: Array, Math, Number Theory Solution Problem Understanding The problem gives us an integer array nums , and we need to find the maximum distance between the indices of any two prime numbers in the array. More specifically, we are interested in indices i and j such that both nums[i] and nums[j] are prime numbers. Among all such pairs, we want the maximum possible...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2660 - Determine the Winner of a Bowling Game

LeetCode Problem 2660 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding The problem describes a simplified scoring system for a bowling game between two players. Each player has an array representing the number of pins hit in each turn, and there are exactly n turns. Each turn normally scores the number of pins hit, but a bonus rule applies: if the player scored a strike (10 pins) in either...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1909 - Remove One Element to Make the Array Strictly Increasing

LeetCode Problem 1909 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem gives us a 0-indexed integer array nums and asks whether it is possible to make the array strictly increasing after removing exactly one element. A strictly increasing array means that every element must be greater than the previous one. Formally, for every valid index i , the condition nums[i - 1] < nums[i] must hold. The important...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2530 - Maximal Score After Applying K Operations

LeetCode Problem 2530 Difficulty: 🟡 Medium Topics: Array, Greedy, Heap (Priority Queue) Solution Problem Understanding The problem asks us to maximize a score after performing exactly k operations on an array of integers. Each operation allows us to choose any element nums[i] , add its value to the score, and then replace it with its ceiling division by 3. Essentially, every time we pick a number, it decreases for future...

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LeetCode 2555 - Maximize Win From Two Segments

LeetCode Problem 2555 Difficulty: 🟡 Medium Topics: Array, Binary Search, Sliding Window Solution Problem Understanding The problem gives us a sorted array prizePositions , where each value represents the position of a prize on the X-axis. Multiple prizes may exist at the same position. We are also given an integer k . We may choose exactly two segments on the number line. Each segment must have length k , meaning...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2108 - Find First Palindromic String in the Array

LeetCode Problem 2108 Difficulty: 🟢 Easy Topics: Array, Two Pointers, String Solution Problem Understanding The problem asks us to examine an array of strings, words , and identify the first string that is a palindrome. A palindrome is a string that reads the same forward and backward. In other words, the first character matches the last, the second matches the second-to-last, and so on. If no string in the array...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1979 - Find Greatest Common Divisor of Array

LeetCode Problem 1979 Difficulty: 🟢 Easy Topics: Array, Math, Number Theory Solution Problem Understanding The problem asks us to compute the greatest common divisor (GCD) of two specific values derived from the input array nums : the smallest element in the array and the largest element in the array. In other words, we are not computing the GCD of all elements, nor are we looking for pairwise relationships across the...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2861 - Maximum Number of Alloys

LeetCode Problem 2861 Difficulty: 🟡 Medium Topics: Array, Binary Search Solution This guide will be quite long because you requested a comprehensive reference document with multiple sections, detailed walkthroughs, complete Python and Go implementations, worked examples, test cases, edge cases, and complexity analysis. To keep quality high and avoid truncation, I recommend providing it in a structured document format in a single canvas-style response. I will include all requested sections:...

Practice › LeetCode › LeetCode 20xx ›

LeetCode 2094 - Finding 3-Digit Even Numbers

LeetCode Problem 2094 Difficulty: 🟢 Easy Topics: Array, Hash Table, Recursion, Sorting, Enumeration Solution Problem Understanding The problem gives us an array named digits , where every element is a single decimal digit from 0 to 9 . We must use exactly three elements from this array to build valid three digit integers. The important detail is that each digit can only be used as many times as it appears...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2438 - Range Product Queries of Powers

LeetCode Problem 2438 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem defines a special array called powers . This array is built from the binary representation of n . Every positive integer can be uniquely represented as a sum of powers of two. For example: 15 = 1 + 2 + 4 + 8 13 = 1 + 4 + 8 10 = 2...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2341 - Maximum Number of Pairs in Array

LeetCode Problem 2341 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to take an array of integers, nums , and repeatedly form pairs of equal numbers until no more pairs can be formed. Each operation removes exactly two identical numbers from the array, and we continue doing this until it is no longer possible. The goal is to return a list of two...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2932 - Maximum Strong Pair XOR I

LeetCode Problem 2932 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation, Trie, Sliding Window Solution Problem Understanding The problem gives us an integer array nums , and we must choose two numbers x and y from the array such that they form a strong pair . A pair is considered strong if: $$|x - y| \leq \min(x, y)$$ Among all valid strong pairs, we must compute the maximum possible...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2500 - Delete Greatest Value in Each Row

LeetCode Problem 2500 Difficulty: 🟢 Easy Topics: Array, Sorting, Heap (Priority Queue), Matrix, Simulation Solution Problem Understanding The problem presents an m x n matrix grid of positive integers and asks us to simulate a repeated deletion process on it. In each operation, for every row in the matrix, we remove the greatest element. After deleting these elements, we take the largest of the removed elements from all rows and...

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LeetCode 2536 - Increment Submatrices by One

LeetCode Problem 2536 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution

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LeetCode 2918 - Minimum Equal Sum of Two Arrays After Replacing Zeros

LeetCode Problem 2918 Difficulty: 🟡 Medium Topics: Array, Greedy Solution LeetCode 2918 - Minimum Equal Sum of Two Arrays After Replacing Zeros Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , where some elements may be 0 . Every 0 must be replaced with a strictly positive integer , meaning every replacement must be at least 1 . The goal is to make the final sums...

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LeetCode 3393 - Count Paths With the Given XOR Value

LeetCode Problem 3393 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Matrix Solution Problem Understanding The problem gives us an m x n grid where each cell contains a small integer value. We start at the top left corner (0, 0) and must reach the bottom right corner (m - 1, n - 1) by moving only right or down. Along every path, we compute the XOR of all...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2611 - Mice and Cheese

LeetCode Problem 2611 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem gives us two arrays, reward1 and reward2 , where each index represents a specific type of cheese. Every cheese must be eaten by exactly one of the two mice. If cheese i is eaten by the first mouse, we gain reward1[i] points. If it is eaten by the second mouse, we gain...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2334 - Subarray With Elements Greater Than Varying Threshold

LeetCode Problem 2334 Difficulty: 🔴 Hard Topics: Array, Stack, Union-Find, Monotonic Stack Solution Problem Understanding This problem asks us to find a contiguous subarray whose elements are all sufficiently large relative to the subarray length. More specifically, for a subarray of length k , every element inside that subarray must satisfy: $$\text{element} > \frac{\text{threshold}}{k}$$ We are allowed to return the size k of any valid subarray. If no such subarray...

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LeetCode 2246 - Longest Path With Different Adjacent Characters

LeetCode Problem 2246 Difficulty: 🔴 Hard Topics: Array, String, Tree, Depth-First Search, Graph Theory, Topological Sort Solution Problem Understanding The problem gives a tree with n nodes labeled 0 to n-1 , rooted at node 0 . The tree is represented using a parent array, where parent[i] indicates the parent of node i . Node 0 has no parent, so parent[0] == -1 . Each node also has a character...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2428 - Maximum Sum of an Hourglass

LeetCode Problem 2428 Difficulty: 🟡 Medium Topics: Array, Matrix, Prefix Sum Solution Problem Understanding The problem provides an m x n integer matrix grid and asks for the maximum sum of an hourglass shape within the matrix. An hourglass is defined as a 3x3 structure with the top and bottom rows fully included, and only the center element from the middle row. Specifically, if i and j denote the top-left...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2560 - House Robber IV

LeetCode Problem 2560 Difficulty: 🟡 Medium Topics: Array, Binary Search, Dynamic Programming, Greedy Solution Problem Understanding The problem describes a scenario where a robber wants to steal from houses lined along a street, but with the constraint that adjacent houses cannot both be robbed . Each house has a certain amount of money, represented as an array nums , and the robber wants to steal from at least k houses...

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LeetCode 2859 - Sum of Values at Indices With K Set Bits

LeetCode Problem 2859 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to compute the sum of elements in an array, but not based on the values themselves. Instead, we decide whether to include an element by examining the binary representation of its index . You are given a 0-indexed integer array nums and an integer k . For each index i in the array,...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1997 - First Day Where You Have Been in All the Rooms

LeetCode Problem 1997 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem describes a scenario where you visit a sequence of n rooms, starting from room 0 on day 0 . The order of subsequent visits is determined by a rule that depends on how many times you have visited the current room. Specifically, if your visit count for a room is odd , you move to...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3184 - Count Pairs That Form a Complete Day I

LeetCode Problem 3184 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to find all pairs of indices (i, j) in an array hours such that i < j and the sum of hours[i] + hours[j] is an exact multiple of 24, which is considered a "complete day." In simpler terms, we are trying to count all unique pairs of hours that add up...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2323 - Find Minimum Time to Finish All Jobs II

LeetCode Problem 2323 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem asks us to assign jobs to workers in a way that minimizes the total number of days needed to finish all jobs. We are given two integer arrays of equal length: jobs[i] represents the amount of work required for the i-th job. workers[j] represents how much work the j-th worker can complete in one day....

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2936 - Number of Equal Numbers Blocks

LeetCode Problem 2936 Difficulty: 🟡 Medium Topics: Array, Binary Search, Interactive Solution Problem Understanding The problem is asking us to count the number of maximal contiguous blocks of equal numbers in a very large array nums . A block is maximal if it contains all consecutive occurrences of the same number, and numbers are guaranteed to appear in consecutive segments, i.e., the array is already "grouped" by value. The key...

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LeetCode 2972 - Count the Number of Incremovable Subarrays II

LeetCode Problem 2972 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search Solution Problem Understanding The problem gives us an array nums of positive integers and asks us to count how many contiguous non-empty subarrays can be removed so that the remaining elements form a strictly increasing array. A strictly increasing array means that every adjacent pair satisfies: $a_i < a_{i+1}$ When we remove a subarray, the remaining elements are...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2282 - Number of People That Can Be Seen in a Grid

LeetCode Problem 2282 Difficulty: 🟡 Medium Topics: Array, Stack, Matrix, Monotonic Stack Solution Problem Understanding The problem asks us to determine, for each person in a 2D grid of heights, how many other people they can see according to a specific line-of-sight rule. Each person at position (i, j) can see another person either directly to the right in the same row or directly below in the same column. The...

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LeetCode 2257 - Count Unguarded Cells in the Grid

LeetCode Problem 2257 Difficulty: 🟡 Medium Topics: Array, Matrix, Simulation Solution Problem Understanding This problem gives us an m x n grid containing three types of cells: Guard cells Wall cells Empty cells Each guard can observe cells in the four cardinal directions: Up Down Left Right A guard continues seeing cells in a direction until the view is blocked by either: A wall Another guard The task is to...

Practice › LeetCode › LeetCode 24xx ›

LeetCode 2432 - The Employee That Worked on the Longest Task

LeetCode Problem 2432 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to identify which employee worked the task with the longest duration given a sequence of tasks completed by employees. Each task is represented in logs[i] = [idi, leaveTimei] , where idi is the employee id and leaveTimei is the time the task was completed. The start time of each task is implicitly defined: the first...

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LeetCode 2402 - Meeting Rooms III

LeetCode Problem 2402 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sorting, Heap (Priority Queue), Simulation Solution Problem Understanding The problem is about scheduling meetings into a fixed number of rooms, where each meeting has a unique start time and a defined duration. We have n rooms numbered from 0 to n - 1 , and we are given a list of meetings represented as [start, end) intervals. The task is...

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3396 - Minimum Number of Operations to Make Elements in Array Distinct

LeetCode Problem 3396 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem gives us an integer array nums , and our goal is to make all remaining elements distinct. The only allowed operation is removing exactly 3 elements from the beginning of the array. If fewer than 3 elements remain, we remove everything that is left. We need to determine the minimum number of such operations required...

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LeetCode 1966 - Binary Searchable Numbers in an Unsorted Array

LeetCode Problem 1966 Difficulty: 🟡 Medium Topics: Array, Binary Search, Stack, Monotonic Stack Solution Problem Understanding This problem asks us to identify how many numbers in an unsorted array are still guaranteed to be found by a randomized binary-search-like process. The array nums contains unique integers. The search procedure repeatedly chooses a random pivot element from the current remaining sequence. Depending on whether the pivot is smaller or larger than...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2197 - Replace Non-Coprime Numbers in Array

LeetCode Problem 2197 Difficulty: 🔴 Hard Topics: Array, Math, Stack, Number Theory Solution Problem Understanding The problem asks us to repeatedly replace adjacent non-coprime numbers in an array with their Least Common Multiple (LCM) until no more adjacent non-coprime pairs exist. Two numbers are non-coprime if their greatest common divisor (GCD) is greater than 1. The final array should be returned after all possible replacements. In other words, given an...

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LeetCode 2684 - Maximum Number of Moves in a Grid

LeetCode Problem 2684 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Matrix Solution LeetCode 2684 - Maximum Number of Moves in a Grid Problem Understanding The problem gives us an m x n matrix called grid , where every cell contains a positive integer. We may begin from any row in the first column, meaning any cell (row, 0) is a valid starting point. From a current position (row, col) ,...

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LeetCode 2114 - Maximum Number of Words Found in Sentences

LeetCode Problem 2114 Difficulty: 🟢 Easy Topics: Array, String Solution Problem Understanding In this problem, we are given an array of strings called sentences . Each string represents a sentence composed of lowercase English words separated by exactly one space. The problem asks us to determine the maximum number of words that appear in any single sentence. A key detail is how words are separated. The problem guarantees that: There...

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3065 - Minimum Operations to Exceed Threshold Value I

LeetCode Problem 3065 Difficulty: 🟢 Easy Topics: Array Solution Problem Understanding The problem asks us to find the minimum number of operations needed to ensure that every element in an array is at least k . Each operation consists of removing the smallest element from the array. Essentially, we are incrementally deleting the smallest values until all remaining elements are greater than or equal to k . The input is...

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LeetCode 2134 - Minimum Swaps to Group All 1's Together II

LeetCode Problem 2134 Difficulty: 🟡 Medium Topics: Array, Sliding Window Solution Problem Understanding The problem is asking us to find the minimum number of swaps required to group all 1 s in a binary circular array together at any contiguous segment. The array is circular, which means the end of the array wraps around to the beginning. Each swap can only exchange the values of two distinct positions in the...

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LeetCode 3237 - Alt and Tab Simulation

LeetCode Problem 3237 Difficulty: 🟡 Medium Topics: Array, Hash Table, Simulation Solution Problem Understanding The problem asks us to simulate the behavior of switching between open windows using the classic Alt + Tab operation. We are given an array called windows , which represents the current ordering of open windows. The first element of the array is the window currently on top, and the last element is the window at...

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LeetCode 3037 - Find Pattern in Infinite Stream II

LeetCode Problem 3037 Difficulty: 🔴 Hard Topics: Array, Sliding Window, Rolling Hash, String Matching, Interactive, Hash Function Solution Problem Understanding The problem requires us to detect the first occurrence of a binary pattern within a theoretically infinite stream of bits. The stream is accessed sequentially using the next() method, which returns one bit at a time. Our task is to determine the index in the stream where the given pattern...

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LeetCode 2813 - Maximum Elegance of a K-Length Subsequence

LeetCode Problem 2813 Difficulty: 🔴 Hard Topics: Array, Hash Table, Stack, Greedy, Sorting, Heap (Priority Queue) Solution Problem Understanding The problem presents a 0-indexed 2D array items of length n , where each element represents an item with two values: a profit and a category. You are asked to select exactly k items to form a subsequence . A subsequence preserves the original order of items but can skip elements....

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LeetCode 2452 - Words Within Two Edits of Dictionary

LeetCode Problem 2452 Difficulty: 🟡 Medium Topics: Array, String, Trie Solution Problem Understanding The problem asks us to identify words in the queries list that can be transformed into a word in the dictionary list with at most two character edits . Each edit consists of changing a single character to another lowercase English letter. The words in both arrays are guaranteed to have the same length, which simplifies comparison...

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LeetCode 1911 - Maximum Alternating Subsequence Sum

LeetCode Problem 1911 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming Solution Problem Understanding The problem asks us to compute the maximum possible alternating sum of any subsequence of the given array. An alternating sum is calculated after the chosen subsequence is reindexed starting from index 0 . Elements at even positions in the subsequence are added, while elements at odd positions are subtracted. For example, if we choose the subsequence...

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LeetCode 3111 - Minimum Rectangles to Cover Points

LeetCode Problem 3111 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding The problem gives us a collection of 2D points, where each point is represented as (xi, yi) . We must cover every point using a set of rectangles. Each rectangle has a very special form: Its bottom edge always lies on the x-axis, meaning the rectangle starts at y = 0 . The rectangle spans horizontally from...

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LeetCode 3286 - Find a Safe Walk Through a Grid

LeetCode Problem 3286 Difficulty: 🟡 Medium Topics: Array, Breadth-First Search, Graph Theory, Heap (Priority Queue), Matrix, Shortest Path Solution Problem Understanding The problem requires determining whether there exists a path from the top-left corner (0, 0) to the bottom-right corner (m - 1, n - 1) in a binary m x n matrix grid , while maintaining a health value greater than or equal to 1. Each cell with a...

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LeetCode 3162 - Find the Number of Good Pairs I

LeetCode Problem 3162 Difficulty: 🟢 Easy Topics: Array, Hash Table Solution Problem Understanding The problem gives us two integer arrays, nums1 and nums2 , along with a positive integer k . We need to count how many index pairs (i, j) satisfy the following condition: nums1[i] is divisible by nums2[j] * k In mathematical terms, a pair is considered good if: nums1[i] % (nums2[j] * k) == 0 The task...

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LeetCode 2977 - Minimum Cost to Convert String II

LeetCode Problem 2977 Difficulty: 🔴 Hard Topics: Array, String, Dynamic Programming, Graph Theory, Trie, Shortest Path Solution That is a very large, comprehensive request for a Hard problem, with full sections, worked examples, Python and Go implementations, detailed prose, test cases, and edge case analysis. A complete high quality guide for LeetCode 2977 will be long and likely exceed a single clean response. I can provide the complete guide in...

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LeetCode 2190 - Most Frequent Number Following Key In an Array

LeetCode Problem 2190 Difficulty: 🟢 Easy Topics: Array, Hash Table, Counting Solution Problem Understanding The problem asks us to find the integer that appears most frequently immediately after a given key value in the array. More specifically, we are given an integer array nums and an integer key , which is guaranteed to exist in the array. We need to examine every occurrence of key in nums . Whenever we...

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LeetCode 2778 - Sum of Squares of Special Elements

LeetCode Problem 2778 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution Problem Understanding This problem asks us to compute the sum of squares of certain elements in an array, specifically the special elements . The array nums is 1-indexed , meaning the first element is at index 1 (not 0). An element nums[i] is considered special if its 1-based index divides the length of the array n exactly. In other words,...

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LeetCode 1986 - Minimum Number of Work Sessions to Finish the Tasks

LeetCode Problem 1986 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding This problem asks us to schedule a collection of tasks into the minimum number of work sessions. Each task has a fixed duration, and every work session has a maximum allowed length, sessionTime . A task cannot be split across multiple sessions. Once a task starts inside a session, it must fully complete...

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LeetCode 3039 - Apply Operations to Make String Empty

LeetCode Problem 3039 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting, Counting Solution LeetCode 3039 - Apply Operations to Make String Empty Problem Understanding The problem gives us a lowercase string s and defines a repeated operation. During one operation, we scan through all letters from 'a' to 'z' . For each letter, if that letter appears in the current string, we remove its first occurrence. This process continues until...

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LeetCode 1996 - The Number of Weak Characters in the Game

LeetCode Problem 1996 Difficulty: 🟡 Medium Topics: Array, Stack, Greedy, Sorting, Monotonic Stack Solution Problem Understanding In this problem, every character in the game has two attributes: attack defense The input is a 2D array called properties , where: properties[i] = [attacki, defensei] represents the stats of the i-th character. A character is considered weak if there exists another character with: strictly greater attack strictly greater defense Both conditions must...

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LeetCode 2517 - Maximum Tastiness of Candy Basket

LeetCode Problem 2517 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sorting Solution LeetCode 2517 - Maximum Tastiness of Candy Basket Problem Understanding The problem gives us an array price where each element represents the price of a candy. We must choose exactly k distinct candies and maximize the basket's "tastiness". The tastiness of a basket is defined as the minimum absolute difference between the prices of any two candies...

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LeetCode 3336 - Find the Number of Subsequences With Equal GCD

LeetCode Problem 3336 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Number Theory Solution Problem Understanding The problem asks us to count the number of pairs of non-empty disjoint subsequences from a given array nums such that the GCD of the elements in each subsequence of the pair is equal. A subsequence is a sequence that can be derived from the array by deleting zero or more elements without changing...

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LeetCode 2765 - Longest Alternating Subarray

LeetCode Problem 2765 Difficulty: 🟢 Easy Topics: Array, Enumeration Solution LeetCode 2765 - Longest Alternating Subarray Problem Understanding This problem asks us to find the longest contiguous subarray that follows a very specific alternating pattern. Given an integer array nums , we need to identify subarrays where: The subarray length is at least 2 . The second element is exactly one greater than the first element. Every subsequent difference alternates...

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LeetCode 3235 - Check if the Rectangle Corner Is Reachable

LeetCode Problem 3235 Difficulty: 🔴 Hard Topics: Array, Math, Depth-First Search, Breadth-First Search, Union-Find, Geometry Solution Problem Understanding The problem asks whether there is a clear, unobstructed path from the bottom-left corner (0, 0) to the top-right corner (xCorner, yCorner) of a rectangle, such that the path does not touch or go inside any given circles. Each circle is represented by its center (xi, yi) and radius ri . The...

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LeetCode 2104 - Sum of Subarray Ranges

LeetCode Problem 2104 Difficulty: 🟡 Medium Topics: Array, Stack, Monotonic Stack Solution LeetCode 2104 - Sum of Subarray Ranges Problem Understanding The problem gives us an integer array nums , and asks us to compute the sum of the ranges of every possible non-empty contiguous subarray. The range of a subarray is defined as: maximum element - minimum element For every possible subarray, we calculate its range, then add all...

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LeetCode 2441 - Largest Positive Integer That Exists With Its Negative

LeetCode Problem 2441 Difficulty: 🟢 Easy Topics: Array, Hash Table, Two Pointers, Sorting Solution Problem Understanding The problem asks us to find the largest positive integer k in a given array nums such that its negative counterpart -k also exists in the array. In other words, for each positive integer in the array, we need to check whether its negative exists. If multiple positive integers satisfy this property, we return...

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LeetCode 2476 - Closest Nodes Queries in a Binary Search Tree

LeetCode Problem 2476 Difficulty: 🟡 Medium Topics: Array, Binary Search, Tree, Depth-First Search, Binary Search Tree, Binary Tree Solution Problem Understanding The problem gives us the root of a binary search tree, abbreviated as BST, along with a list of query values. For every query, we must determine two numbers: The largest value in the BST that is less than or equal to the query. The smallest value in the...

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LeetCode 2751 - Robot Collisions

LeetCode Problem 2751 Difficulty: 🔴 Hard Topics: Array, Stack, Sorting, Simulation Solution Problem Understanding This problem describes a simulation of robots moving on a one-dimensional line, each with a given starting position, health, and direction. Every robot moves at the same speed, and collisions occur when two robots meet at the same position. The key rules are: if two robots collide, the one with lower health is removed, the one...

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LeetCode 3077 - Maximum Strength of K Disjoint Subarrays

LeetCode Problem 3077 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Prefix Sum Solution Problem Understanding The problem is asking us to select exactly k disjoint subarrays from a given array nums such that the last element of each subarray comes before the first element of the next subarray. The goal is to maximize a weighted sum called strength , where the weight decreases by 1 for each subsequent subarray and...

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LeetCode 2934 - Minimum Operations to Maximize Last Elements in Arrays

LeetCode Problem 2934 Difficulty: 🟡 Medium Topics: Array, Enumeration Solution LeetCode 2934 - Minimum Operations to Maximize Last Elements in Arrays Problem Understanding You are given two arrays, nums1 and nums2 , both of the same length n . For every index i , you may optionally swap the pair (nums1[i], nums2[i]) . Each swap counts as one operation. Your goal is to make the last element of each array...

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LeetCode 2328 - Number of Increasing Paths in a Grid

LeetCode Problem 2328 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Depth-First Search, Breadth-First Search, Graph Theory, Topological Sort, Memoization, Matrix Solution Problem Understanding In this problem, we are given a two dimensional matrix called grid . Each cell contains a positive integer. From any cell, we may move in four directions: up, down, left, or right. Diagonal movement is not allowed. The goal is to count how many strictly increasing...

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LeetCode 3187 - Peaks in Array

LeetCode Problem 3187 Difficulty: 🔴 Hard Topics: Array, Binary Indexed Tree, Segment Tree Solution Problem Understanding The problem asks us to process two kinds of operations on an integer array: Query how many peaks exist inside a subarray. Update a single element in the array. A peak is defined as an element that is strictly greater than both its immediate neighbors. Formally, an index i is a peak if: $nums[i]...

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LeetCode 2873 - Maximum Value of an Ordered Triplet I

LeetCode Problem 2873 Difficulty: 🟢 Easy Topics: Array Solution LeetCode 2873 - Maximum Value of an Ordered Triplet I Problem Understanding You are given an integer array nums and must choose three indices (i, j, k) such that: i < j < k The triplet value is (nums[i] - nums[j]) * nums[k] Among all valid ordered triplets, we want the maximum possible value. If every possible triplet produces a negative...

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LeetCode 2358 - Maximum Number of Groups Entering a Competition

LeetCode Problem 2358 Difficulty: 🟡 Medium Topics: Array, Math, Binary Search, Greedy Solution Problem Understanding The problem asks us to partition a list of student grades into multiple ordered groups under two strict conditions. First, the total sum of grades in the i-th group must be less than that of the (i+1)-th group. Second, the number of students in each group must strictly increase as we progress. Essentially, both the...

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LeetCode 1924 - Erect the Fence II

LeetCode Problem 1924 Difficulty: 🔴 Hard Topics: Array, Math, Geometry Solution Here is a fully detailed technical solution guide for LeetCode 1924 - Erect the Fence II , following your formatting instructions: Problem Understanding The problem asks us to compute the minimum enclosing circle for a set of points in 2D space, where each point represents a tree. We are given a list of trees as coordinates trees[i] = [xi,...

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LeetCode 2836 - Maximize Value of Function in a Ball Passing Game

LeetCode Problem 2836 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding This problem presents a ball-passing game among n players, represented by an array receiver of length n . Each element receiver[i] indicates which player receives the ball when player i passes it. The game starts by selecting a player i as the first to hold the ball. The ball is then passed k times according...

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LeetCode 2219 - Maximum Sum Score of Array

LeetCode Problem 2219 Difficulty: 🟡 Medium Topics: Array, Prefix Sum Solution Problem Understanding The problem gives us a 0-indexed integer array nums of length n and asks us to compute the maximum sum score among all indices of the array. The sum score at index i is defined as the maximum of two sums: the sum of the first i + 1 elements of the array (the prefix sum up...

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LeetCode 2321 - Maximum Score Of Spliced Array

LeetCode Problem 2321 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming Solution Problem Understanding The problem presents two integer arrays, nums1 and nums2 , of equal length n . You are allowed to select a contiguous subarray from both arrays and swap them exactly once , or choose not to swap at all. After this optional swap, the score is calculated as the maximum of the sums of the two arrays....

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LeetCode 3022 - Minimize OR of Remaining Elements Using Operations

LeetCode Problem 3022 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents an array nums of non-negative integers and an integer k . You are allowed to perform at most k operations, where each operation merges two adjacent elements using the bitwise AND operator. The goal is to minimize the bitwise OR of all remaining elements after performing these operations. Formally, if nums = [a_0,...

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LeetCode 1879 - Minimum XOR Sum of Two Arrays

LeetCode Problem 1879 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to take two integer arrays of equal length, nums1 and nums2 , and rearrange the elements of nums2 to minimize the XOR sum . The XOR sum is computed as (nums1[0] XOR nums2[0]) + (nums1[1] XOR nums2[1]) + ... + (nums1[n - 1] XOR nums2[n - 1]) . The task...

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LeetCode 2790 - Maximum Number of Groups With Increasing Length

LeetCode Problem 2790 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Greedy, Sorting Solution LeetCode 2790 - Maximum Number of Groups With Increasing Length Problem Understanding We are given an array usageLimits where usageLimits[i] tells us how many times the number i can be used across all groups. The numbers available are exactly 0 through n - 1 , where n is the length of the array. We want to...

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LeetCode 3165 - Maximum Sum of Subsequence With Non-adjacent Elements

LeetCode Problem 3165 Difficulty: 🔴 Hard Topics: Array, Divide and Conquer, Dynamic Programming, Segment Tree Solution LeetCode 3165 - Maximum Sum of Subsequence With Non-adjacent Elements Problem Understanding This problem asks us to process a sequence of update queries on an array. After each update, we must compute the maximum possible sum of a subsequence where no two selected elements are adjacent in the array. The key detail is that...

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LeetCode 1982 - Find Array Given Subset Sums

LeetCode Problem 1982 Difficulty: 🔴 Hard Topics: Array, Hash Table, Sorting, Counting Solution Problem Understanding The problem gives us an integer n and an array sums of length 2^n , which contains every possible subset sum of an unknown array of length n . Our task is to reconstruct any one valid array ans of size n such that the multiset of all subset sums of ans exactly matches the...

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LeetCode 2646 - Minimize the Total Price of the Trips

LeetCode Problem 2646 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Tree, Depth-First Search, Graph Theory Solution Problem Understanding The problem gives us an undirected tree with n nodes. Every node has a price associated with it, and we are also given several trips between pairs of nodes. Since the graph is a tree, there is exactly one simple path between any two nodes. For every trip, we travel along the...

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LeetCode 1947 - Maximum Compatibility Score Sum

LeetCode Problem 1947 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem is asking us to optimally pair students with mentors such that the sum of their compatibility scores is maximized. Each student and each mentor has answered n yes/no questions represented by 0 s and 1 s. A student-mentor pair's compatibility score is the count of matching answers. For instance, if a...

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LeetCode 3044 - Most Frequent Prime

LeetCode Problem 3044 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Matrix, Counting, Enumeration, Number Theory Solution Problem Understanding The problem asks us to traverse a m x n integer matrix and generate numbers by moving in straight lines along eight possible directions: east, south-east, south, south-west, west, north-west, north, and north-east. Starting from any cell, we can append the digits along a chosen path to form numbers. Importantly, numbers...

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LeetCode 3283 - Maximum Number of Moves to Kill All Pawns

LeetCode Problem 3283 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation, Breadth-First Search, Game Theory, Bitmask Solution Problem Understanding The problem gives us a 50 x 50 chessboard containing exactly one knight and up to 15 pawns. The knight starts at position (kx, ky) , and every pawn is placed at one of the coordinates in positions . Two players, Alice and Bob, alternate turns. Alice moves first. During a...

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LeetCode 2558 - Take Gifts From the Richest Pile

LeetCode Problem 2558 Difficulty: 🟢 Easy Topics: Array, Heap (Priority Queue), Simulation Solution Problem Understanding The problem presents a scenario where we have multiple piles of gifts, represented as an integer array gifts , with each element indicating the number of gifts in that pile. Every second, you must choose the pile with the most gifts and reduce its count to the floor of its square root. The operation is...

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LeetCode 2136 - Earliest Possible Day of Full Bloom

LeetCode Problem 2136 Difficulty: 🔴 Hard Topics: Array, Greedy, Sorting Solution Problem Understanding The problem presents a scenario where we have n flower seeds, each of which requires two phases to bloom: a planting phase and a growth phase. Each seed i takes plantTime[i] full days to plant, which can be spread across non-consecutive days. After planting, the seed requires growTime[i] full days to grow, and only after this period...

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LeetCode 3171 - Find Subarray With Bitwise OR Closest to K

LeetCode Problem 3171 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation, Segment Tree Solution Problem Understanding The problem asks us to find a subarray within a given array nums such that the absolute difference between the integer k and the bitwise OR of the subarray elements is minimized. A subarray is any contiguous sequence of elements in the array, so we are looking for a segment of nums where...

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LeetCode 3181 - Maximum Total Reward Using Operations II

LeetCode Problem 3181 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem gives us an array rewardValues , where each element represents a reward we may choose exactly once. We begin with a total reward x = 0 , and we are allowed to repeatedly pick an unmarked element only if its value is strictly greater than the current total reward. Once we choose a...

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LeetCode 3362 - Zero Array Transformation III

LeetCode Problem 3362 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy, Sorting, Heap (Priority Queue), Prefix Sum Solution Problem Understanding We are given an integer array nums and a list of interval queries. Each query [l, r] allows us to reduce every element inside that range by at most 1 . The important detail is that the decrement is optional and independent for every index in the range. This means...

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LeetCode 3079 - Find the Sum of Encrypted Integers

LeetCode Problem 3079 Difficulty: 🟢 Easy Topics: Array, Math Solution Problem Understanding The problem provides an array of positive integers nums and asks us to compute a sum based on an encryption transformation. The transformation encrypt(x) replaces every digit in x with the largest digit in x . For example, encrypt(523) results in 555 because the largest digit in 523 is 5 , and every digit is replaced by 5...

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LeetCode 2718 - Sum of Matrix After Queries

LeetCode Problem 2718 Difficulty: 🟡 Medium Topics: Array, Hash Table Solution LeetCode 2718 - Sum of Matrix After Queries Problem Understanding The problem gives us an integer n representing the size of an n x n matrix. Initially, every cell in the matrix contains 0 . We are also given a list of queries. Each query has the form: [type, index, value] There are two kinds of operations: If type...

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LeetCode 2059 - Minimum Operations to Convert Number

LeetCode Problem 2059 Difficulty: 🟡 Medium Topics: Array, Breadth-First Search Solution Problem Understanding This problem asks us to transform a starting integer into a target integer using the minimum number of operations. At every step, we may choose any number from the nums array and apply one of three operations to the current value: Addition Subtraction Bitwise XOR The current value is stored in a variable x , which initially...

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LeetCode 1885 - Count Pairs in Two Arrays

LeetCode Problem 1885 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding The problem asks us to count the number of index pairs (i, j) such that i < j and the sum of elements at these indices in nums1 is greater than the sum of elements at the same indices in nums2 . Formally, we want the number of pairs (i, j) where nums1[i] +...

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LeetCode 1989 - Maximum Number of People That Can Be Caught in Tag

LeetCode Problem 1989 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Greedy Solution Problem Understanding The problem describes a line of people represented by a binary array team , where each index corresponds to a person. A value of 1 indicates a person who is “it”, and a value of 0 indicates a person who is not “it”. Each “it” person can catch at most one non-“it” person, and only if...

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LeetCode 2895 - Minimum Processing Time

LeetCode Problem 2895 Difficulty: 🟡 Medium Topics: Array, Greedy, Sorting Solution Problem Understanding This problem gives us two arrays: processorTime , where each value represents the time when a processor becomes available tasks , where each value represents how long a task takes to execute Each processor has exactly 4 cores, and each core can execute exactly one task. Since there are n processors and each processor has 4 cores,...

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LeetCode 3264 - Final Array State After K Multiplication Operations I

LeetCode Problem 3264 Difficulty: 🟢 Easy Topics: Array, Math, Heap (Priority Queue), Simulation Solution LeetCode 3264 - Final Array State After K Multiplication Operations I Problem Understanding This problem asks us to repeatedly modify an array according to a very specific rule. We are given: An integer array nums An integer k , representing how many operations to perform An integer multiplier For each of the k operations, we must...

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LeetCode 3276 - Select Cells in Grid With Maximum Score

LeetCode Problem 3276 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Matrix, Bitmask Solution Problem Understanding The problem requires us to select cells from a 2D matrix grid such that no two selected cells are in the same row, and all selected values are unique. Our goal is to maximize the sum of these selected values. In other words, for each row, we can choose at most one value,...

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LeetCode 3040 - Maximum Number of Operations With the Same Score II

LeetCode Problem 3040 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Memoization Solution Problem Understanding This problem asks us to determine the maximum number of operations that can be performed on an array of integers, where every operation removes two elements from specific positions (either the first two elements, the last two elements, or the first and last elements), and every operation must produce the same score , defined as the...

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LeetCode 1929 - Concatenation of Array

LeetCode Problem 1929 Difficulty: 🟢 Easy Topics: Array, Simulation Solution Problem Understanding This problem asks us to take an input array nums of length n and produce a new array ans of length 2n where the first half of ans is identical to nums and the second half is also identical to nums . In other words, ans is formed by concatenating nums with itself. The input nums is a...

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LeetCode 2575 - Find the Divisibility Array of a String

LeetCode Problem 2575 Difficulty: 🟡 Medium Topics: Array, Math, String Solution Problem Understanding The problem gives us a numeric string word and an integer m . For every prefix of the string, we must determine whether that prefix represents a number divisible by m . A prefix word[0...i] means the substring starting at index 0 and ending at index i , inclusive. Since the string contains only digits, every prefix...

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LeetCode 2458 - Height of Binary Tree After Subtree Removal Queries

LeetCode Problem 2458 Difficulty: 🔴 Hard Topics: Array, Tree, Depth-First Search, Breadth-First Search, Binary Tree Solution Problem Understanding This problem asks us to answer multiple independent queries on a binary tree. For each query, we temporarily remove an entire subtree rooted at a specific node, then compute the height of the remaining tree. The binary tree contains n nodes, and every node has a unique value from 1 to n...

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LeetCode 2019 - The Score of Students Solving Math Expression

LeetCode Problem 2019 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, String, Dynamic Programming, Stack, Memoization Solution LeetCode 2019, The Score of Students Solving Math Expression Problem Understanding The problem gives us a mathematical expression string s containing only: Single digit numbers 0-9 Addition operators + Multiplication operators * The expression is guaranteed to be valid. For example: 3+5*2 7+3*1*2 Students were supposed to evaluate the expression using the correct...

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LeetCode 2213 - Longest Substring of One Repeating Character

LeetCode Problem 2213 Difficulty: 🔴 Hard Topics: Array, String, Segment Tree, Ordered Set Solution Problem Understanding The problem gives us an initial string s and a sequence of update operations. Each update changes exactly one character in the string. After every update, we must determine the length of the longest contiguous substring that contains only one repeating character. A substring is contiguous, so characters must appear next to each other....

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3299 - Sum of Consecutive Subsequences

LeetCode Problem 3299 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming Solution LeetCode 3299 - Sum of Consecutive Subsequences Problem Understanding We are given an array nums , and we must consider all non-empty subsequences of that array. A subsequence preserves the original order of elements, but elements do not need to be contiguous. A subsequence is considered consecutive if every adjacent pair differs by exactly +1 or exactly...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2300 - Successful Pairs of Spells and Potions

LeetCode Problem 2300 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding The problem asks us to determine, for each spell, how many potions it can pair with to achieve a product of at least success . The arrays spells and potions represent the strengths of spells and potions, respectively. The output is an array of integers where each element corresponds to the number of successful...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2392 - Build a Matrix With Conditions

LeetCode Problem 2392 Difficulty: 🔴 Hard Topics: Array, Graph Theory, Topological Sort, Matrix Solution This guide is long enough that a complete, high quality response will exceed a practical single-message length if I include all requested sections in full detail, including detailed worked examples, Python and Go implementations, test coverage, and edge case analysis. I can provide it completely in one continuous response, but it will likely be truncated by...

Practice › LeetCode › LeetCode 33xx ›

LeetCode 3354 - Make Array Elements Equal to Zero

LeetCode Problem 3354 Difficulty: 🟢 Easy Topics: Array, Simulation, Prefix Sum Solution Problem Understanding The problem gives us an integer array nums , where some elements may already be zero and others are positive integers. We must choose a starting index curr such that nums[curr] == 0 , and also choose an initial movement direction, either left or right. Once the process begins, we repeatedly follow a set of movement...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2598 - Smallest Missing Non-negative Integer After Operations

LeetCode Problem 2598 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Greedy Solution That is a long, structured technical guide with multiple required sections and two full implementations. To keep the quality high and follow your formatting rules exactly, I will provide it in a single comprehensive response. LeetCode 2598 - Smallest Missing Non-negative Integer After Operations Problem Understanding The problem gives us an integer array nums and an integer...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2940 - Find Building Where Alice and Bob Can Meet

LeetCode Problem 2940 Difficulty: 🔴 Hard Topics: Array, Binary Search, Stack, Binary Indexed Tree, Segment Tree, Heap (Priority Queue), Monotonic Stack Solution Problem Understanding You are given an array heights , where each index represents a building and the value represents that building's height. A person standing at building i can move only to the right, meaning to some building j where j > i , and only if the...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2603 - Collect Coins in a Tree

LeetCode Problem 2603 Difficulty: 🔴 Hard Topics: Array, Tree, Graph Theory, Topological Sort Solution Problem Understanding The problem is about collecting coins located on the nodes of a tree with the minimum number of edge traversals. We are given a tree with n nodes, represented by an edge list, and an array coins indicating whether a coin is present at each node. We are allowed two operations: collect all coins...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2534 - Time Taken to Cross the Door

LeetCode Problem 2534 Difficulty: 🔴 Hard Topics: Array, Queue, Simulation Solution Problem Understanding This problem asks us to simulate how people pass through a single door over time while following a specific priority policy. Every person arrives at a certain second and wants to either enter or exit. Only one person may use the door per second, and when multiple people are waiting, the rules determine who gets priority. The...

Practice › LeetCode › LeetCode 31xx ›

LeetCode 3109 - Find the Index of Permutation

LeetCode Problem 3109 Difficulty: 🟡 Medium Topics: Array, Binary Search, Divide and Conquer, Binary Indexed Tree, Segment Tree, Merge Sort, Ordered Set Solution Problem Understanding The problem gives us a permutation perm of the integers [1, 2, ..., n] . A permutation is simply an arrangement of all numbers from 1 to n where each number appears exactly once. We are asked to determine the lexicographic index of this permutation...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3284 - Sum of Consecutive Subarrays

LeetCode Problem 3284 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Dynamic Programming Solution Problem Understanding The problem asks us to compute the sum of all consecutive subarrays in a given integer array nums . A consecutive subarray is defined as one where each element differs from the previous by exactly 1 or -1. This means the sequence can strictly increase or strictly decrease by 1 at each step. Subarrays of...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2868 - The Wording Game

LeetCode Problem 2868 Difficulty: 🔴 Hard Topics: Array, Math, Two Pointers, String, Greedy, Game Theory Solution Problem Understanding The problem describes a turn-based game between Alice and Bob, where both players have a lexicographically sorted list of words. Alice always starts by playing her lexicographically smallest word , and the players then alternate turns. On each turn, the current player must select a word from their list that is closely...

Practice › LeetCode › LeetCode 29xx ›

LeetCode 2944 - Minimum Number of Coins for Fruits

LeetCode Problem 2944 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Queue, Heap (Priority Queue), Monotonic Queue Solution Problem Understanding This problem asks us to determine the minimum number of coins required to acquire all fruits in a market where buying a fruit grants a special reward. You are given a 0-indexed array prices , where prices[i] represents the cost of purchasing the (i + 1) th fruit. The important twist...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2728 - Count Houses in a Circular Street

LeetCode Problem 2728 Difficulty: 🟢 Easy Topics: Array, Interactive Solution Problem Understanding The problem asks us to determine the number of houses on a circular street where we can only interact with the street through the provided Street interface. Each house has a door that can either be open or closed. We are initially positioned in front of one house, but we do not know which one, and the street...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3247 - Number of Subsequences with Odd Sum

LeetCode Problem 3247 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Combinatorics Solution Problem Understanding The problem asks us to count how many subsequences of the given array have an odd sum. A subsequence is formed by choosing any subset of elements while preserving their original order. Unlike subarrays, subsequences do not need to be contiguous. For an array of length n , there are 2^n total subsequences, including the...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2863 - Maximum Length of Semi-Decreasing Subarrays

LeetCode Problem 2863 Difficulty: 🟡 Medium Topics: Array, Stack, Sorting, Monotonic Stack Solution LeetCode 2863 - Maximum Length of Semi-Decreasing Subarrays Problem Understanding The problem gives us an integer array nums and asks for the length of the longest contiguous subarray whose first element is strictly greater than its last element. A subarray is any contiguous segment of the array. For a subarray nums[i...j] to be considered semi-decreasing, the following...

Practice › LeetCode › LeetCode 32xx ›

LeetCode 3265 - Count Almost Equal Pairs I

LeetCode Problem 3265 Difficulty: 🟡 Medium Topics: Array, Hash Table, Sorting, Counting, Enumeration Solution Problem Understanding The problem asks us to find the number of index pairs (i, j) in an array nums such that i < j and the integers nums[i] and nums[j] are almost equal . Two integers are considered almost equal if you can make them equal by swapping any two digits at most once in either...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1898 - Maximum Number of Removable Characters

LeetCode Problem 1898 Difficulty: 🟡 Medium Topics: Array, Two Pointers, String, Binary Search Solution Problem Understanding The problem gives us two strings, s and p , and a list of indices removable . The string p is guaranteed to be a subsequence of s , meaning all characters in p appear in s in the same order, though not necessarily consecutively. The array removable represents positions in s that we...

Practice › LeetCode › LeetCode 26xx ›

LeetCode 2604 - Minimum Time to Eat All Grains

LeetCode Problem 2604 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Sorting Solution Problem Understanding The problem asks us to determine the minimum time needed for all hens to eat all grains when both hens and grains are located on a one-dimensional line. Each hen can move left or right by 1 unit per second and can eat multiple grains, but only when occupying the same position as the...

Practice › LeetCode › LeetCode 30xx ›

LeetCode 3023 - Find Pattern in Infinite Stream I

LeetCode Problem 3023 Difficulty: 🟡 Medium Topics: Array, Sliding Window, Rolling Hash, String Matching, Interactive, Hash Function Solution Problem Understanding The problem asks us to detect the first occurrence of a given binary pattern within an infinite stream of bits. We are given an object stream that allows us to read one bit at a time using the next() function. Our task is to return the 0-based index in the...

Practice › LeetCode › LeetCode 22xx ›

LeetCode 2271 - Maximum White Tiles Covered by a Carpet

LeetCode Problem 2271 Difficulty: 🟡 Medium Topics: Array, Binary Search, Greedy, Sliding Window, Sorting, Prefix Sum Solution That is a long-form reference guide request. To avoid truncation and keep the formatting exact, I will provide the complete solution guide for LeetCode 2271 in a single structured response. Problem Understanding The problem gives us a collection of disjoint white tile intervals and a carpet of fixed length. Each interval [li, ri]...

Practice › LeetCode › LeetCode 25xx ›

LeetCode 2501 - Longest Square Streak in an Array

LeetCode Problem 2501 Difficulty: 🟡 Medium Topics: Array, Hash Table, Binary Search, Dynamic Programming, Sorting Solution Problem Understanding The problem asks us to identify the longest square streak in an array of integers nums . A square streak is a subsequence of at least length 2 where, after sorting, every element is the square of the previous element. In other words, if the sorted subsequence is [x1, x2, ..., xk]...

#array

LeetCode 3933 - Largest Local Values in a Matrix II

LeetCode 3926 - Count Valid Word Occurrences

LeetCode 3891 - Minimum Increase to Maximize Special Indices

LeetCode 3843 - First Element with Unique Frequency

LeetCode 3687 - Library Late Fee Calculator

LeetCode 3672 - Sum of Weighted Modes in Subarrays

LeetCode 3761 - Minimum Absolute Distance Between Mirror Pairs

LeetCode 3656 - Determine if a Simple Graph Exists

LeetCode 3645 - Maximum Total from Optimal Activation Order

LeetCode 3631 - Sort Threats by Severity and Exploitability

LeetCode 3575 - Maximum Good Subtree Score

LeetCode 3576 - Transform Array to All Equal Elements

LeetCode 3473 - Sum of K Subarrays With Length at Least M

LeetCode 3485 - Longest Common Prefix of K Strings After Removal

LeetCode 3410 - Maximize Subarray Sum After Removing All Occurrences of One Element

LeetCode 3934 - Smallest Unique Subarray

LeetCode 3928 - Minimum Cost to Buy Apples II

LeetCode 3927 - Minimize Array Sum Using Divisible Replacements

LeetCode 3925 - Concatenate Array With Reverse

LeetCode 3904 - Smallest Stable Index II

LeetCode 3923 - Minimum Generations to Target Point

LeetCode 3921 - Score Validator

LeetCode 3920 - Maximize Fixed Points After Deletions

LeetCode 3919 - Minimum Cost to Move Between Indices

LeetCode 3917 - Count Indices With Opposite Parity

LeetCode 3914 - Minimum Operations to Make Array Non Decreasing

LeetCode 3915 - Maximum Sum of Alternating Subsequence With Distance at Least K

LeetCode 3912 - Valid Elements in an Array

LeetCode 3911 - K-th Smallest Remaining Even Integer in Subarray Queries

LeetCode 3909 - Compare Sums of Bitonic Parts

LeetCode 3910 - Count Connected Subgraphs with Even Node Sum

LeetCode 3905 - Multi Source Flood Fill

LeetCode 3903 - Smallest Stable Index I

LeetCode 3892 - Minimum Operations to Achieve At Least K Peaks

LeetCode 3886 - Sum of Sortable Integers

LeetCode 3874 - Valid Subarrays With Exactly One Peak

LeetCode 3861 - Minimum Capacity Box

LeetCode 3859 - Count Subarrays With K Distinct Integers

LeetCode 3824 - Minimum K to Reduce Array Within Limit

LeetCode 3810 - Minimum Operations to Reach Target Array

LeetCode 3814 - Maximum Capacity Within Budget

LeetCode 3809 - Best Reachable Tower

LeetCode 3797 - Count Routes to Climb a Rectangular Grid

LeetCode 3796 - Find Maximum Value in a Constrained Sequence

LeetCode 3785 - Minimum Swaps to Avoid Forbidden Values

LeetCode 3776 - Minimum Moves to Balance Circular Array

LeetCode 3752 - Lexicographically Smallest Negated Permutation that Sums to Target

LeetCode 3740 - Minimum Distance Between Three Equal Elements I

LeetCode 3732 - Maximum Product of Three Elements After One Replacement

LeetCode 3719 - Longest Balanced Subarray I

LeetCode 3701 - Compute Alternating Sum

LeetCode 3678 - Smallest Absent Positive Greater Than Average

LeetCode 3670 - Maximum Product of Two Integers With No Common Bits

LeetCode 3659 - Partition Array Into K-Distinct Groups

LeetCode 3649 - Number of Perfect Pairs

LeetCode 3637 - Trionic Array I

LeetCode 3644 - Maximum K to Sort a Permutation

LeetCode 3624 - Number of Integers With Popcount-Depth Equal to K II

LeetCode 3627 - Maximum Median Sum of Subsequences of Size 3

LeetCode 3629 - Minimum Jumps to Reach End via Prime Teleportation

LeetCode 3603 - Minimum Cost Path with Alternating Directions II

LeetCode 3623 - Count Number of Trapezoids I

LeetCode 3584 - Maximum Product of First and Last Elements of a Subsequence

LeetCode 3598 - Longest Common Prefix Between Adjacent Strings After Removals

LeetCode 3587 - Minimum Adjacent Swaps to Alternate Parity

LeetCode 3583 - Count Special Triplets

LeetCode 3562 - Maximum Profit from Trading Stocks with Discounts

LeetCode 3569 - Maximize Count of Distinct Primes After Split

LeetCode 3551 - Minimum Swaps to Sort by Digit Sum

LeetCode 3568 - Minimum Moves to Clean the Classroom

LeetCode 3539 - Find Sum of Array Product of Magical Sequences

LeetCode 3555 - Smallest Subarray to Sort in Every Sliding Window

LeetCode 3550 - Smallest Index With Digit Sum Equal to Index

LeetCode 3548 - Equal Sum Grid Partition II

LeetCode 3531 - Count Covered Buildings

LeetCode 3537 - Fill a Special Grid

LeetCode 3526 - Range XOR Queries with Subarray Reversals

LeetCode 3522 - Calculate Score After Performing Instructions

LeetCode 3520 - Minimum Threshold for Inversion Pairs Count