Generated by Codex with GPT-5
MEDIUMArray, Sorting, Heap (Priority Queue), Simulation, Prefix SumA car has a fixed number of seats and only travels east. Each trip is described as [passengers, pickup, dropoff]: the passengers enter at pickup and leave at dropoff.
Generated by Codex with GPT-5
MEDIUMArray, Binary SearchThere is a line of packages, each with a weight. A ship moves packages in the given order, and each day it can carry packages only until the total loaded weight reaches its capacity. The task is to find the smallest ship capacity that can move every package within days days.
Generated by Codex with GPT-5
MEDIUMArray, Hash Table, String, SortingThe input is a base string s and three parallel arrays:
indices[i] says where a possible replacement starts.sources[i] says what text must already appear there.targets[i] says what text to write if the source matches.Every replacement is checked against the original string, not against a partially edited string. That “simultaneous” detail is the core of the problem. If s = "abcd", indices = [0, 2], sources = ["a", "cd"], and targets = ["eee", "ffff"], both checks happen on "abcd", so the answer is "eeebffff".
Generated by Codex with GPT-5
MEDIUMDynamic Programming, Depth-First Search, Breadth-First Search, Graph Theory, Heap (Priority Queue), Shortest PathThere are n cities, and each directed flight has a departure city, an arrival city, and a price. Given src, dst, and k, return the cheapest price from src to dst using at most k stops. If no such route exists, return -1.
Generated by Codex with GPT-5
MEDIUMTree, Depth-First Search, Breadth-First Search, Binary TreeThe input is the root of a binary tree. The task is to find the largest width across all levels.
The subtle part is how width is defined. It is not just the number of real nodes on a level. The width runs from the leftmost real node to the rightmost real node on that level, counting the missing null positions between them as if the tree were laid out like a complete binary tree.
Continue ...Generated by Codex with GPT-5
MEDIUMArray, Two Pointers, Binary Search, Sliding Window, Sorting, Heap (Priority Queue)The input is already sorted. Given a target value x, the task is to return the k values that are closest to it, still in sorted order.
Generated by Codex with GPT-5
MEDIUMArray, Graph Theory, Topological SortThe input gives a target sequence nums and a list of shorter sequences. Each shorter sequence says, “these numbers must appear in this relative order.”
The task is not just to ask whether nums can be built from those constraints. It asks whether nums is the only shortest sequence that satisfies every constraint. If another sequence of the same shortest length can also satisfy the constraints, the answer is False.
Generated by Codex with GPT-5
MEDIUMArray, Hash Table, SortingThe input is an array nums of length n. Every value is in the range 1 through n, and each value appears either once or twice. The task is to return every value that appears twice.
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.