Generated by Codex with GPT-5
MEDIUMArray, Dynamic ProgrammingThe input is an array of positive integers. The task is to decide whether the array can be split into two subsets whose sums are exactly equal.
Continue ...Generated by Codex with GPT-5
HARDArray, Hash Table, Divide and Conquer, Segment Tree, Prefix SumThe input is an integer array. A subarray is balanced when the number of distinct even values inside it equals the number of distinct odd values inside it. Repeated copies of the same number only count once, so [3, 2, 2, 5, 4] has two distinct odd values, 3 and 5, and two distinct even values, 2 and 4.
Generated by Claude with claude-opus-4-7
Design, Heap (Priority Queue), Data StreamDesign a collection that supports two operations in any interleaving:
insert(num) — add a number to the collection.find_kth_largest(k) — return the k-th largest element currently in the collection.The twist versus the original LeetCode 703 is that k is a parameter of every query and may change from call to call. The classic min-heap-of-size-k solution relied on k being fixed at construction so it could safely discard everything below the running k-th largest. Once k can grow on a later call, no element is safe to throw away, and the whole strategy has to change.
Generated by Codex with GPT-5
HARDSerialization, Depth-First Search, Hash Table, Graph, DesignThe task is to write an encoder that accepts an input value and returns the same kind of string a normal JSON serializer would return:
Continue ...Generated by Codex with GPT-5
MEDIUMMath, Bit ManipulationThe task is to return the sum of two signed integers without using the + or - operators. The important constraint is not about math knowledge; it is about understanding how binary addition works under the hood.
Generated by Codex with GPT-5
MEDIUMString, Stack, Greedy, Monotonic StackThe problem gives a non-negative integer as a string and asks for the smallest possible number after removing exactly k digits. The answer must not keep unnecessary leading zeroes, and if every digit is removed or the remaining digits are all zeroes, the answer is "0".
Generated by Codex with GPT-5
MEDIUMArray, Sliding Window, Prefix Sum, Greedy, MathThis is a special case of the necklace splitting problem: two people, two bead
types, and therefore at most two cuts. The input is a necklace represented as an
array containing only X and Y. Suppose the full array has:
Generated by Codex with GPT-5
MEDIUMArray, Binary Search, Divide and Conquer, MatrixThe matrix is sorted in two directions at once. Every row is sorted from left to right, and every column is sorted from top to bottom. Given a target value, the task is to decide whether the target appears anywhere in the matrix.
Continue ...Generated by Codex with GPT-5
MEDIUMMath, Dynamic Programming, Breadth-First SearchGiven a positive integer n, the task is to return the fewest perfect square numbers whose sum is exactly n. A perfect square is a number such as 1, 4, 9, 16, and so on.
Generated by Codex with GPT-5
MEDIUMArray, Design, Matrix, Prefix SumThe class receives a fixed 2D matrix and must answer many rectangle-sum queries. Each query gives the top-left cell (row1, col1) and the bottom-right cell (row2, col2), and asks for the sum of every matrix value inside that inclusive rectangle.