#data structures

CF 958C3 - Encryption (hard) Rating: 2500 Tags: data structures, dp Model: gpt-5-3-mini Solve time: 4m 21s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a339db1-3c50-83ec-9b14-c27aeee268ad Solution Problem Understanding We are given a long sequence of positive integers and asked to cut it into exactly k contiguous segments. Each segment must be non-empty and every element must belong to exactly one segment. For any segment, we compute its sum, then reduce that sum...

CF 1041D - Glider Rating: 1700 Tags: binary search, data structures, two pointers Model: gpt-5-3-mini Solve time: 1m 35s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a337e1b-8584-83ec-825a-6d7235a7a6fb Solution Problem Understanding A glider is released from a moving airplane at some integer x-coordinate while the plane is fixed at height h. Once released, the glider always moves one unit to the right per second. At the same time, its height decreases by one...

CF 925E - May Holidays Rating: 2900 Tags: data structures, trees Model: gpt-5-3-mini Solve time: 1m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32ffff-94fc-83ec-89c8-10abb82f5c3d Solution Problem Understanding We are given a company hierarchy that forms a rooted tree, where employee 1 is the root. Every other employee has exactly one direct manager, so each node has a parent pointer and the structure has no cycles. The subtree of a node represents...

CF 1106B - Lunar New Year and Food Ordering Rating: 1500 Tags: data structures, implementation Model: gpt-5-3-mini Solve time: 1m 8s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a3382a8-9dcc-83ec-b94f-73baabc02245 Solution Problem Understanding We are given a restaurant with several types of dishes. Each type has a current stock and a fixed price per dish. Customers arrive one by one, and each customer requests a specific type of dish multiple times. For each...

CF 1042F - Leaf Sets Rating: 2400 Tags: data structures, dfs and similar, dsu, graphs, greedy, sortings, trees Model: gpt-5-5 Solve time: 1m 22s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33bd15-e528-83ec-b5a4-de0286e26609 Solution Problem Understanding We are given a tree where only some vertices matter: those with degree exactly one, which we call leaves. The task is not about grouping all vertices, but only about grouping these leaves. Each group must satisfy...

CF 940F - Machine Learning Rating: 2600 Tags: brute force, data structures Model: gpt-5-3-mini Solve time: 1m 38s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a339941-b930-83ec-ade4-8af56ecaf742 Solution Problem Understanding We are given an array that changes over time and we must support two operations on it. The first operation asks us to look at a subarray and, for every possible value v , compute how many times v appears inside that segment....

CF 1037F - Maximum Reduction Rating: 2500 Tags: combinatorics, data structures, math Model: gpt-5-3-mini Solve time: 5m 7s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33b6ee-5a88-83ec-87f4-ff56d9af8bf4 Solution Problem Understanding The process repeatedly transforms an array by replacing every contiguous block of length k with its maximum value, and accumulating the sum of those block maxima at each stage. After forming the new array from all sliding window maxima, the same operation is...

CF 983D - Arkady and Rectangles Rating: 3300 Tags: data structures Model: gpt-5-3-mini Solve time: 3m 22s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33a72f-4124-83ec-bf18-f5d71d97cab4 Solution Problem Understanding We are given a plane that starts completely white, meaning every point initially has color 0. Then we place up to 100,000 axis-aligned rectangles one after another. Each rectangle is painted with a unique color equal to its index in the input order, and...

CF 923B - Producing Snow Rating: 1600 Tags: binary search, data structures Model: gpt-5-3-mini Solve time: 2m 45s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a339128-9068-83ec-9ae9-9b98168b3b3f Solution Problem Understanding Each day, Bob adds a new pile of snow with a fixed initial volume. From that day onward, every existing pile loses the same amount of volume every day, determined by that day’s temperature. If a pile’s remaining volume becomes zero or negative...

CF 999D - Equalize the Remainders Rating: 1900 Tags: data structures, greedy, implementation Model: gpt-5-3-mini Solve time: 5m 9s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33b125-bd44-83ec-93e2-228ea245c0a3 Solution Problem Understanding We are given an array of integers, and we are allowed to repeatedly increase any single element by one. The cost is the number of such increments. The real constraint is not about the values themselves but about their residues modulo a...

CF 982D - Shark Rating: 1900 Tags: brute force, data structures, dsu, trees Model: gpt-5-3-mini Solve time: 1m 4s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33a645-49b4-83ec-b927-8bcea72bc401 Solution Problem Understanding We are given a sequence of distinct positive integers representing daily travel distances of a shark observed over time. We introduce a threshold value $k$. Each day is classified as either a “stay day” if the distance is less than $k$, or...

CF 960F - Pathwalks Rating: 2100 Tags: data structures, dp, graphs Model: gpt-5-3-mini Solve time: 4m 24s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33a06c-a550-83ec-baf9-e569323b4a6a Solution Problem Understanding We are given a directed graph where each edge has an associated weight and also an implicit position given by its order in the input. A valid path is not constrained to be simple; vertices may repeat, and we may traverse edges multiple times...

CF 961E - Tufurama Rating: 1900 Tags: data structures Model: gpt-5-3-mini Solve time: 4m 30s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33a1ef-c17c-83ec-a5bc-2567d5118a47 Solution Problem Understanding We are given a collection of TV seasons. Season i contains a[i] episodes, numbered from 1 up to a[i] . We want to count pairs of distinct seasons (x, y) with x < y such that two conditions are simultaneously possible: Season x has at least...

CF 1042D - Petya and Array Rating: 1800 Tags: data structures, divide and conquer, two pointers Model: gpt-5-3-mini Solve time: 1m 19s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a337e74-0c8c-83ec-89c6-71e8972be404 Solution Problem Understanding We are given a sequence of integers laid out in a row, and we are interested in contiguous fragments of this row. For every possible fragment, we compute its sum, and we need to count how many of these...

CF 1070E - Getting Deals Done Rating: 2100 Tags: binary search, data structures Model: gpt-5-3-mini Solve time: 1m 33s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33bee1-54b8-83ec-8078-dc30aeae57f9 Solution Problem Understanding We are given a sequence of tasks, each with a processing time. Polycarp scans tasks from left to right and decides whether to execute or skip each one based on a threshold value $d$. Any task with duration greater than $d$ is...

CF 981G - Magic multisets Rating: 2500 Tags: data structures Model: gpt-5-3-mini Solve time: 1m 24s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33a5ef-e170-83ec-9d4e-609a11808222 Solution Problem Understanding We are given an array of positions from 1 to n, and at each position there is a multiset that starts empty. We perform two types of operations over ranges of these positions. The first operation applies a value x to every multiset in a...

CF 986E - Prince's Problem Rating: 2800 Tags: brute force, data structures, math, number theory, trees Model: gpt-5-3-mini Solve time: 1m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33a912-486c-83ec-87ce-50fb9a999e6f Solution Problem Understanding We are working with a tree of up to 100,000 vertices. Each vertex stores a positive integer value. For every query, we are given two vertices and a number $x$. The query asks us to walk along the unique...

CF 932B - Recursive Queries Rating: 1300 Tags: binary search, data structures, dfs and similar Model: gpt-5-3-mini Solve time: 1m 34s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a32e3b7-e7dc-83ec-a17b-6d7184217e41 Solution Problem Understanding We are given a function defined on positive integers that repeatedly transforms a number by taking its digit product and then collapsing it again in a recursive way until a single digit remains. That final digit is what we call...

CF 946G - Almost Increasing Array Rating: 2500 Tags: data structures, dp Model: gpt-5-3-mini Solve time: 52s Verified: yes (1/1 samples) Solution Problem Understanding We are given a sequence of integers and we are allowed to change values arbitrarily, paying one unit cost per changed position. After we finish editing the array, we want the result to become “almost increasing”, meaning that if we delete at most one element from...

CF 982B - Bus of Characters Rating: 1300 Tags: data structures, greedy, implementation Model: gpt-5-5 Solve time: 1m 4s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a337532-184c-83ec-bd9a-f66c9654df9d Solution Problem Understanding The bus consists of $n$ independent rows, each row containing exactly two seats. Each row has a fixed width $w_i$, and all widths are distinct, so we can always compare rows without ambiguity. Passengers arrive one by one in a fixed order....

CF 926J - Segments Rating: 2100 Tags: data structures Model: gpt-5-3-mini Solve time: 1m 11s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33017b-0364-83ec-8f99-d2bb3134596f Solution Problem Understanding We are maintaining a growing set of closed intervals on a number line. Initially, nothing is painted. One by one, segments are added, and after each insertion we want to know how many disjoint black regions exist if we take the union of all segments seen...

CF 1041F - Ray in the tube Rating: 2500 Tags: data structures, divide and conquer, dp, math Model: gpt-5-3-mini Solve time: 1m 39s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a33bb87-06c0-83ec-b667-3f627d49e575 Solution Problem Understanding We are given two horizontal lines, each containing a set of integer x-coordinates where sensors are placed. The lower line has height $y_1$, the upper line has height $y_2$, and $y_1 < y_2$. We choose one point $A$...

CF 960H - Santa's Gift Rating: 3100 Tags: data structures, trees Model: gpt-5-3-mini Solve time: 1m 41s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a33a0ca-b98c-83ec-bcc1-c68b68835be7 Solution Problem Understanding We are working on a rooted tree where each vertex contains exactly one candy, and each candy has a flavour. The tree structure is fixed, but the flavours change over time through updates. For a fixed flavour $k$, imagine we repeatedly pick a vertex...

CF 899E - Segments Removal Rating: 2000 Tags: data structures, dsu, flows, implementation, two pointers Model: gpt-5-5 Solve time: 1m 28s Verified: yes (1/1 samples) Solution Problem Understanding The array starts as a sequence of integers, and it evolves through a very specific greedy deletion rule. At any moment you look at all maximal blocks of consecutive equal values, pick the block with the largest length, and if several blocks...

CF 938G - Shortest Path Queries Rating: 2900 Tags: bitmasks, data structures, dsu, graphs Model: gpt-5-3-mini Solve time: 2m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32799a-0180-83ec-8ea1-490a97920b8d Solution Problem Understanding We are maintaining a graph whose edges carry integer weights, but distance is not defined in the usual additive sense. Instead, when you walk along a path, the cost of that path is the bitwise XOR of all edge weights along...

CF 936E - Iqea Rating: 3400 Tags: data structures, dfs and similar, divide and conquer, dsu, shortest paths, trees Model: gpt-5-3-mini Solve time: 2m 13s Verified: yes (1/1 samples) Solution Problem Understanding We are given a set of cells on a large grid. Each cell is a city, and roads exist between any two cities that share an edge on the grid. The important geometric constraints are that the chosen...

CF 995C - Leaving the Bar Rating: 2300 Tags: brute force, data structures, geometry, greedy, math, sortings Model: gpt-5-3-mini Solve time: 1m 17s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a329559-3654-83ec-b447-c240f12e5b40 Solution Problem Understanding We are given a sequence of planar displacement vectors, each representing a move from the origin or from the current position. For every vector, we are allowed to choose its direction independently: we either add it as given...

CF 900C - Remove Extra One Rating: 1700 Tags: brute force, data structures, math Model: gpt-5-5 Solve time: 1m 49s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a326bf7-e158-83ec-93da-3ee651a8b97a Solution Problem Understanding We are given a permutation and we look at it from left to right, marking a position as a “record” whenever its value is strictly larger than everything seen before it. Equivalently, records are the positions where a new prefix maximum...

CF 938D - Buy a Ticket Rating: 2000 Tags: data structures, graphs, shortest paths Model: gpt-5-3-mini Solve time: 2m Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32790c-167c-83ec-bdc2-cbedf9f20620 Solution Problem Understanding We are given a weighted undirected graph where cities are vertices and train routes are edges with travel costs. Each city also has a fixed price for buying a concert ticket in that city. For any starting city, a person may travel...

CF 961B - Lecture Sleep Rating: 1200 Tags: data structures, dp, implementation, two pointers Model: gpt-5-3-mini Solve time: 1m 14s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a3280b1-1f98-83ec-b0ee-5785d1836f05 Solution Problem Understanding The lecture is a sequence of minutes, and during each minute the lecturer produces a certain number of theorems. If Mishka is awake at that minute, those theorems are recorded; if he is asleep, they are lost. The twist is that...

CF 926E - Merge Equal Elements Rating: 1900 Tags: constructive algorithms, data structures Model: gpt-5-3-mini Solve time: 1m 5s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a3270f4-c654-83ec-aadf-ab79419d4fc3 Solution Problem Understanding We are given a sequence of positive integers, arranged in a line. The process repeatedly looks for two identical numbers that sit next to each other. Whenever such a pair exists, the leftmost such pair is chosen, both elements are removed, and...

CF 992E - Nastya and King-Shamans Rating: 2500 Tags: binary search, data structures Model: gpt-5-3-mini Solve time: 1m 19s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32940b-b21c-83ec-b060-e3a9e4fcea32 Solution Problem Understanding We are given a sequence of values representing shamans ordered by time. Each position holds a “power”, and we continuously update single positions. After every update, we must determine whether there exists an index $j$ such that the value at $j$ equals...

CF 896C - Willem, Chtholly and Seniorious Rating: 2600 Tags: data structures, probabilities Model: gpt-5-3-mini Solve time: 4m 17s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32b526-b83c-83ec-9899-997a323cb749 Solution Problem Understanding We are working with a dynamic array of up to 100,000 integers, and we must support a sequence of 100,000 operations. Each operation modifies a contiguous segment or queries information about a segment. There are two update operations: one adds a value...

CF 923C - Perfect Security Rating: 1800 Tags: data structures, greedy, strings, trees Model: gpt-5-3-mini Solve time: 1m 18s Verified: yes (1/1 samples) Solution Problem Understanding We are given two arrays of integers of equal length. One array represents encrypted values, and the other represents a multiset of key values whose order has been lost. Each original message value was combined with one key value using bitwise XOR, but we...

CF 962D - Merge Equals Rating: 1600 Tags: data structures, implementation Model: gpt-5-3-mini Solve time: 1m 36s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a328137-28e8-83ec-9075-4ac30cd1c380 Solution Problem Understanding We are given a sequence of integers arranged left to right. The process repeatedly searches for values that appear at least twice, but it does not pick them arbitrarily. Instead, among all values that currently have duplicates, we always select the smallest such value....

CF 954G - Castle Defense Rating: 2000 Tags: binary search, data structures, greedy, two pointers Model: gpt-5-3-mini Solve time: 1m 46s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a327d26-ccf4-83ec-bcbf-87461eeed768 Solution Problem Understanding Each position on the wall can be thought of as a segment that needs protection strength. You are given an initial arrangement of archers, and each archer does not only defend its own position but also helps nearby positions within...

CF 896E - Welcome home, Chtholly Rating: 3100 Tags: data structures, dsu Model: gpt-5-3-mini Solve time: 1m 27s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32b57e-4280-83ec-a22f-8fa1538f3fba Solution Problem Understanding We are maintaining an array of positive integers that changes over time under two types of range operations. Each element represents a remaining “baking time”, and operations either reduce some values or ask how many elements match an exact target value. The first...

CF 930D - Game with Tokens Rating: 2500 Tags: data structures, games, implementation Model: gpt-5-3-mini Solve time: 1m 49s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a32759f-eca8-83ec-8ce0-6915f5e36d45 Solution Problem Understanding We are given a set of black tokens placed at distinct integer grid points. There is also a single white token whose starting position is not fixed. The game proceeds in alternating turns: white moves first, and on each turn a player...

CF 900E - Maximum Questions Rating: 2100 Tags: data structures, dp, strings Model: gpt-5-3-mini Solve time: 2m 1s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a326c0c-00a4-83ec-b7f9-cc2ecfee4dad Solution Problem Understanding We are given a long text string that contains fixed letters and unknown positions. Each unknown position can later be filled with either 'a' or 'b' . Alongside this, we are also given a pattern string that always alternates, starting with 'a' and...

CF 1271D - Portals Rating: 2100 Tags: data structures, dp, greedy, implementation, sortings Model: gpt-5-3-mini Solve time: 3m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d91d1-6be8-83ec-9b8e-ca8089c0a5e8 Solution Problem Understanding We are given a fixed sequence of castles that must be conquered strictly in order from 1 to n. To conquer castle i, the army must currently have at least a_i warriors. After conquering it, the army does not lose strength, and...

CF 1349A - Orac and LCM Rating: 1600 Tags: data structures, math, number theory Model: gpt-5-3-mini Solve time: 2m 30s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e27f2-7010-83ec-8b4b-dc1d9a6e67c1 Solution Problem Understanding We are given an array of positive integers, and we look at every unordered pair of indices. For each pair, we compute the least common multiple of the two values. This produces a new multiset containing one LCM value per pair....

CF 1368G - Shifting Dominoes Rating: 3200 Tags: data structures, geometry, graphs, trees Model: gpt-5-3-mini Solve time: 5m 46s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e4f95-3500-83ec-8e99-f5fd31a6a1fc Solution Problem Understanding We are given a fully covered grid where every cell belongs to exactly one domino, and every domino occupies two orthogonally adjacent cells. So the input is essentially a perfect matching on the grid graph. After this initial tiling is fixed, Bill...

CF 1373G - Pawns Rating: 2600 Tags: data structures, divide and conquer, greedy Model: gpt-5-3-mini Solve time: 5m 16s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e5b13-8504-83ec-ba02-aa6ed7e2a5da Solution Problem Understanding We are maintaining a dynamic set of pawns on an $n \times n$ grid. Each update toggles a pawn at a specific cell, and after every update we must determine how many extra rows need to be appended on top of the...

CF 1361F - Johnny and New Toy Rating: 3300 Tags: data structures, implementation, math Model: gpt-5-5 Solve time: 5m 8s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e42d3-645c-83ec-83f1-f6612825fe4d Solution Problem Understanding We are given two coupled permutations on the same line of length $n$. One is a permutation $P$ of values $1$ to $n$, and between adjacent elements of $P$ we have edge weights $W_1 \ldots W_{n-1}$, which themselves form a permutation...

CF 1379F1 - Chess Strikes Back (easy version) Rating: 2700 Tags: binary search, data structures Model: gpt-5-3-mini Solve time: 3m 30s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e6458-0154-83ec-bc02-c35ba3e8f716 Solution Problem Understanding We are given a chessboard with $2n$ rows and $2m$ columns. Only the white cells are relevant, and those are exactly the cells where $i + j$ is even. Initially all white cells are usable, but over time some of...

CF 1383E - Strange Operation Rating: 2800 Tags: combinatorics, data structures, dp Model: gpt-5-3-mini Solve time: 3m 27s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e708f-70d4-83ec-86f4-be23546a483f Solution Problem Understanding We are given a binary string and allowed to repeatedly compress adjacent positions. One operation takes two neighbors, merges them into the left position by replacing it with the logical OR of the two bits, then deletes the right position. Repeating this shrinks...

CF 1322E - Median Mountain Range Rating: 3300 Tags: data structures Model: gpt-5-3-mini Solve time: 3m 56s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2debd3-ee88-83ec-81ed-e884ff76ac48 Solution Problem Understanding We are given an array representing heights placed along a straight line. Each day, every interior position updates simultaneously: a position looks at itself and its two neighbors, takes the median of those three values, and becomes that median in the next configuration. The...

CF 1311F - Moving Points Rating: 1900 Tags: data structures, divide and conquer, implementation, sortings Model: gpt-5-3-mini Solve time: 1m 50s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dddac-65f8-83ec-bdff-9c933b0e2972 Solution Problem Understanding We are given a set of points on a number line. Each point starts at some integer position and moves forever in time, each with its own constant velocity. If we pick any two points, their distance changes over time...

CF 1340F - Nastya and CBS Rating: 3300 Tags: brute force, data structures, hashing Model: gpt-5-3-mini Solve time: 2m 14s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e192c-6700-83ec-99f6-87faf42c34b3 Solution Problem Understanding We are given a sequence of integers where each value represents a bracket token. A positive number means an opening bracket of a specific type, and the corresponding negative number is the matching closing bracket of that same type. So the...

CF 1322B - Present Rating: 2100 Tags: binary search, bitmasks, constructive algorithms, data structures, math, sortings Model: gpt-5-3-mini Solve time: 1m 28s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2deae4-fc9c-83ec-aeba-66f8cbbf4563 Solution Problem Understanding We are given an array of integers, and we consider every unordered pair of distinct elements. For each pair, we compute their sum. After collecting all these pairwise sums, instead of summing or minimizing them, we combine them using...

CF 1353D - Constructing the Array Rating: 1600 Tags: constructive algorithms, data structures, sortings Model: gpt-5-3-mini Solve time: 5m 14s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e2f09-bb38-83ec-8c0b-26a2dc3eab95 Solution Problem Understanding We start with an array of length n filled with zeros. We repeatedly “fill” the array in n steps. At each step, we look at the current zero-filled segments and pick one segment to place the next number. The rule for...

CF 1365C - Rotation Matching Rating: 1400 Tags: constructive algorithms, data structures, greedy, implementation Model: gpt-5-3-mini Solve time: 2m 8s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e4979-4b48-83ec-8352-cdd9514f063c Solution Problem Understanding We are given two permutations of the same set of numbers from 1 to n. Think of them as two different circular arrangements of the same labeled tiles. We are allowed to rotate each circle independently any number of times, and...

CF 1380A - Three Indices Rating: 900 Tags: brute force, data structures Model: gpt-5-3-mini Solve time: 4m 33s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e692c-d740-83ec-92fe-7227a6c5eb3c Solution Problem Understanding We are given a permutation, which means every number from 1 to n appears exactly once in some order. The task is to detect a specific pattern of three indices i, j, k with i < j < k such that the value...

CF 1359D - Yet Another Yet Another Task Rating: 2000 Tags: data structures, dp, implementation, two pointers Model: gpt-5-5 Solve time: 4m 32s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e3b68-4258-83ec-a34a-76ee9dcc4897 Solution Problem Understanding We are given an array of integers arranged in a line. Alice first selects any contiguous segment of this array. After that, Bob removes exactly one element from inside that chosen segment. The score is the sum of...

CF 1286D - LCC Rating: 3100 Tags: data structures, math, matrices, probabilities Model: gpt-5-5 Solve time: 4m 42s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2db171-0f54-83ec-a4ab-893275f60814 Solution Problem Understanding We are given a set of particles placed on a number line at distinct positions. Each particle starts at its own position at time zero and immediately chooses a direction: right with probability $p_i$ and left with probability $1 - p_i$. Once directions...

CF 1334F - Strange Function Rating: 2500 Tags: binary search, data structures, dp, greedy Model: gpt-5-5 Solve time: 4m 14s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e0c97-a080-83ec-9041-d62451cff5ef Solution Problem Understanding We are given a sequence of values where each position has a value and a cost of removal. From the original sequence, we are allowed to delete any subset of elements, paying or gaining coins depending on the deletion cost. After...

CF 1313E - Concatenation with intersection Rating: 2700 Tags: data structures, hashing, strings, two pointers Model: gpt-5-3-mini Solve time: 3m 20s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2de325-48b4-83ec-b5e4-21871b1e6570 Solution Problem Understanding We are given two strings of equal length, call them the first and second source strings, and a target string. We are allowed to pick any contiguous segment from the first string and any contiguous segment from the second string,...

CF 1348F - Phoenix and Memory Rating: 2600 Tags: data structures, dfs and similar, graphs, greedy Model: gpt-5-3-mini Solve time: 3m 38s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e260b-7944-83ec-b0a5-2cf38808ad6a Solution Problem Understanding Each position in the final lineup comes with a constraint: at position i , the person sitting there must have a label from a contiguous range [a_i, b_i] . The labels themselves form a permutation of 1 to n...

CF 1346H - Game with Segments Rating: 2700 Tags: *special, data structures, games Model: gpt-5-3-mini Solve time: 2m 21s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e23b1-4140-83ec-9c31-41f2c214dfd1 Solution Problem Understanding We are given an interval on a number line as a starting position, and a collection of special target intervals called terminal segments. A move consists of shrinking the current interval by exactly one unit from either the left side or the...

CF 1294D - MEX maximizing Rating: 1600 Tags: data structures, greedy, implementation, math Model: gpt-5-5 Solve time: 4m 23s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dc457-23f0-83ec-b993-ecf9e885a0f0 Solution Problem Understanding We are building an array one element at a time. After each insertion, we are allowed to “reconfigure” values using a special operation: we can add or subtract a fixed number $x$ to any element, as many times as we want, as...

CF 1278D - Segment Tree Rating: 2100 Tags: data structures, dsu, graphs, trees Model: gpt-5-5 Solve time: 5m 4s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d9e0d-9954-83ec-baf5-8cc431e755d5 Solution Problem Understanding We are given a collection of line segments on a number line. Each segment is defined by two distinct integer endpoints, and no two endpoints coincide anywhere in the input. From these segments we build a graph where each segment is a...

CF 1346F - Dune II: Battle For Arrakis Rating: 2000 Tags: *special, data structures, greedy, math Model: gpt-5-3-mini Solve time: 4m 17s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e23f6-cbe8-83ec-b3d6-17ce363f4940 Solution Problem Understanding The grid represents a battlefield where each cell contains some number of identical units. The goal is to choose one destination cell and move every unit from every other cell into it. A single move shifts exactly one unit...

CF 1379D - New Passenger Trams Rating: 2300 Tags: binary search, brute force, data structures, sortings, two pointers Model: gpt-5-3-mini Solve time: 4m 36s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e6460-6b3c-83ec-8292-9e3f9f8e4c60 Solution Problem Understanding We are given a full-day timetable where freight trains already depart at fixed times. The day is cyclic with h hours and m minutes per hour, so every train time can be treated as a point on...

CF 1320E - Treeland and Viruses Rating: 3000 Tags: data structures, dfs and similar, dp, shortest paths, trees Model: gpt-5-5 Solve time: 7m 20s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2de8a4-e50c-83ec-a13a-1c80b9179d39 Solution Problem Understanding The process happens on a tree of cities. In each scenario, several infection sources are placed on different nodes, each source belonging to a distinct virus type and having a propagation strength. Viruses spread in rounds, and...

CF 1342D - Multiple Testcases Rating: 1900 Tags: binary search, constructive algorithms, data structures, greedy, sortings, two pointers Model: gpt-5-3-mini Solve time: 8m 41s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e1bc3-6528-83ec-be3b-9d57dd5c8d13 Solution Problem Understanding We are given a collection of arrays, but the actual contents of these arrays do not matter at all. Each array is characterized only by its size. Our task is to pack all these arrays into several...

CF 1290B - Irreducible Anagrams Rating: 1800 Tags: binary search, constructive algorithms, data structures, strings, two pointers Model: gpt-5-5 Solve time: 5m 7s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2dbb0a-a9b0-83ec-bfb3-954d543b2b2f Solution Problem Understanding We are given a base string and many queries over its substrings. Each query asks whether the chosen substring admits at least one “irreducible anagram”. To interpret this, imagine we take the substring and consider all possible permutations...

CF 1320A - Journey Planning Rating: 1400 Tags: data structures, dp, greedy, math, sortings Model: gpt-5-5 Solve time: 4m 27s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2de6ec-99fc-83ec-9276-106005ae8eca Solution Problem Understanding We are given a line of cities, each with an index from left to right and an associated beauty value. We need to choose a sequence of cities to visit such that indices strictly increase. The key restriction is that consecutive...

CF 1313C2 - Skyscrapers (hard version) Rating: 1900 Tags: data structures, dp, greedy Model: gpt-5-3-mini Solve time: 8m 40s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2de2e9-3f30-83ec-a421-033d8990a26d Solution Problem Understanding We are given a line of plots, each plot having a maximum allowed building height. We must choose an actual height for each plot, not exceeding its limit, while maximizing the total sum of all chosen heights. The restriction is not local...

CF 1335E1 - Three Blocks Palindrome (easy version) Rating: 1700 Tags: binary search, brute force, data structures, dp, two pointers Model: gpt-5-3-mini Solve time: 3m 26s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e0ec6-5db8-83ec-a770-f21d2987bf2e Solution Problem Understanding We are given a sequence of integers and asked to extract a subsequence that has a very specific structure. The subsequence must look like a block of repeated value x , followed by a block...

CF 1343D - Constant Palindrome Sum Rating: 1700 Tags: brute force, data structures, greedy, two pointers Model: gpt-5-3-mini Solve time: 4m 46s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2e1e83-bbf8-83ec-8cb1-8f509740ced4 Solution Problem Understanding We are given an array of even length, and we look at it as a set of mirrored pairs: the first element is paired with the last, the second with the second last, and so on. For each such...

CF 1369E - DeadLee Rating: 2400 Tags: data structures, dfs and similar, greedy, implementation, sortings Model: gpt-5-3-mini Solve time: 3m 48s Verified: no (0/1 samples) Share: https://chatgpt.com/share/6a2e507d-5c50-83ec-98a0-7e3f660bf5f5 Solution Problem Understanding Each friend is connected to exactly two food types, and each food type has a limited stock of plates. When a friend is called, they attempt to consume one plate from each of their two preferred types. If at least...

CF 1266D - Decreasing Debts Rating: 2000 Tags: constructive algorithms, data structures, graphs, greedy, implementation, math, two pointers Model: gpt-5-3-mini Solve time: 3m 17s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d8730-d1b0-83ec-b40b-a8447d19d422 Solution Problem Understanding We are given a directed weighted graph where each vertex represents a person and each directed edge represents a debt from one person to another. The value on an edge is how much money the source person...

CF 1265B - Beautiful Numbers Rating: 1300 Tags: data structures, implementation, math, two pointers Model: gpt-5-3-mini Solve time: 2m 51s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a2d863c-a648-83ec-8f8b-4b13830ade05 Solution Problem Understanding We are given a permutation of numbers from 1 to n, and we want to classify each value m from 1 to n as either “good” or “bad”. A value m is considered good if somewhere inside the array there exists...

CF 2013F2 - Game in Tree (Hard Version) Rating: 3500 Tags: binary search, data structures, trees Model: gpt-5-5 Solve time: 2m 3s Verified: yes (1/1 samples) Share: https://chatgpt.com/share/6a265c22-e058-83ec-9a73-b3865082b590 Solution Problem Understanding We are given a tree with n vertices. Alice starts at vertex 1 and Bob starts at a vertex along a path between two other nodes, u and v . They take turns moving along unvisited neighboring vertices. A...