Generated by Codex with GPT-5
MEDIUMArray, Binary SearchThe input array was originally sorted in ascending order, then rotated. For example, [0, 1, 2, 4, 5, 6, 7] might become [4, 5, 6, 7, 0, 1, 2].
Generated by Codex with GPT-5
MEDIUMArray, String, Greedy, SortingThe input is a list of non-negative integers. The task is to reorder them so that their decimal representations form the largest possible concatenated number, then return that number as a string.
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MEDIUMArray, Binary Search, Sliding Window, Prefix SumGiven an array of positive integers nums and a positive integer target, find the shortest contiguous subarray whose sum is at least target. If no such subarray exists, return 0.
Generated by Codex with GPT-5
MEDIUMTree, Depth-First Search, Binary Search Tree, Binary TreeA binary search tree should produce values in sorted order when walked with inorder traversal: left subtree, current node, then right subtree. In this problem, exactly two node values were swapped by mistake. The tree shape is still the same, but the values break the BST ordering rule.
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HARDArray, Binary Search, Depth-First Search, Breadth-First Search, Union-Find, Heap (Priority Queue), MatrixThe input is an n x n grid of elevations. At time t, the water level is also t, and a cell is swimmable only if its elevation is at most t.
Generated by Codex with GPT-5
MEDIUMHash Table, MathThe input is a positive integer k. The task is to find the length of the
smallest positive integer made only of the digit 1 that is divisible by k.
Generated by Codex with GPT-5
MEDIUMArray, Binary Search, Greedy, Sliding Window, Sorting, Prefix SumGiven an array of positive integers and a budget k, one operation lets us increase one element by 1. The goal is to make some value appear as many times as possible after using at most k total increments.
Generated by Codex with GPT-5
MEDIUMHash Table, String, Greedy, Heap, CountingThe input is a string s. The task is to rearrange its characters so that no
two adjacent characters are equal. If no such rearrangement exists, return the
empty string. Any valid rearrangement is accepted.
Generated by Codex with GPT-5
HARDArray, GreedyThere are children standing in a line. Each child has a rating, and the goal is to give out the fewest total candies while obeying two rules:
The important detail is that the comparison is only between neighbors. A child does not need more candy than every lower-rated child, only more than the children immediately to the left and right when their rating is higher.
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HARDArray, Dynamic Programming, Depth-First Search, Graph Theory, Topological Sort, Memoization, MatrixThe input is a grid of numbers. From any cell, a path may move only up, down, left, or right, and each move must go to a strictly larger value. The task is to return the maximum number of cells that can appear in any such path.
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