LeetCode 874: Walking Robot Simulation
A clear explanation of simulating robot movement on an infinite grid using direction vectors and obstacle lookup.
Tag
Hash-Set
27 notes
LeetCode 939: Minimum Area Rectangle
A clear explanation of solving Minimum Area Rectangle using diagonal point pairs and constant-time point lookup.
LeetCode 929: Unique Email Addresses
A clear explanation of solving Unique Email Addresses using string normalization and a hash set.
LeetCode 822: Card Flipping Game
A hash set solution for finding the smallest number that can be hidden from all front-facing cards.
LeetCode 820: Short Encoding of Words
A suffix-removal solution for finding the shortest reference string that can encode every word.
LeetCode 817: Linked List Components
A hash set and linked list traversal solution for counting consecutive components whose values appear in nums.
LeetCode 804: Unique Morse Code Words
A set-based solution for counting how many different Morse code transformations appear among a list of words.
LeetCode 752: Open the Lock
A clear explanation of solving Open the Lock using breadth-first search over lock states.
LeetCode 694: Number of Distinct Islands
Count unique island shapes in a binary grid using DFS and relative coordinates.
LeetCode 663: Equal Tree Partition
A clear explanation of checking whether a binary tree can be split into two equal-sum trees by removing one edge.
LeetCode 653: Two Sum IV - Input is a BST
A clear explanation of finding whether two different nodes in a binary search tree sum to a target value.
LeetCode 575: Distribute Candies
A clear explanation of Distribute Candies using a set to count candy types and a simple limit argument.
LeetCode 548: Split Array with Equal Sum
A clear explanation of splitting an array into four equal-sum parts using prefix sums and set-based search.
LeetCode 472: Concatenated Words
A clear explanation of finding all words that can be formed by concatenating at least two shorter words from the same list.
LeetCode 433: Minimum Genetic Mutation
Find the minimum number of valid one-character gene mutations using breadth-first search.
LeetCode 403: Frog Jump
A clear explanation of the Frog Jump problem using dynamic programming with reachable jump sizes.
LeetCode 379: Design Phone Directory
A clear explanation of designing a phone directory that can allocate, check, and release numbers efficiently.
LeetCode 353: Design Snake Game
A clear explanation of implementing Snake Game with a deque for body order and a set for constant-time collision checks.
LeetCode 219: Contains Duplicate II
A clear explanation of detecting whether equal values appear within distance k using a hash map or sliding window set.
LeetCode 217: Contains Duplicate
A clear explanation of detecting duplicates in an array using a hash set and sorting.
LeetCode 202: Happy Number
A clear explanation of detecting whether repeated digit-square sums eventually reach 1.
LeetCode 140: Word Break II
Return all valid sentences formed by inserting spaces into a string so every word belongs to the dictionary, using DFS with memoization.
LeetCode 139: Word Break
Decide whether a string can be segmented into dictionary words using dynamic programming over prefixes.
LeetCode 128: Longest Consecutive Sequence
Find the longest run of consecutive integers in an unsorted array using a hash set and sequence-start detection.
LeetCode 127: Word Ladder
Use breadth-first search to find the shortest transformation sequence length between two words.
LeetCode 126: Word Ladder II
Find all shortest word transformation sequences using BFS to build shortest-path parents, then backtracking to reconstruct every answer.
LeetCode 3: Longest Substring Without Repeating Characters
A clear explanation of the longest substring problem using sliding window and a hash set.