Problem You are given an integer array nums and an integer target. You want to build an expression out of nums by adding one ...

Problem Given a string s, find any substring of length 2 which is also present in the reverse of s. A substring is a contigu...

Problem Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed). https://le...

跟 3218. Minimum Cost for Cutting Cake I 一模一样，只不过 m 和 n 的量级从 20 增加到 10⁵，因此只能用 O(n log n) 贪心解法。 https://leetcode.cn/problems/mi...

Problem There is an m x n cake that needs to be cut into 1 x 1 pieces. You are given integers m, n, and two arrays: horizont...

Problem You are given a directed graph of n nodes numbered from 0 to n - 1, where each node has at most one outgoing edge. Th...

Problem There is a bi-directional graph with n vertices, where each vertex is labeled from 0 to n - 1. The edges in the graph...

Problem There exist two undirected trees with n and m nodes, numbered from 0 to n - 1 and from 0 to m - 1, respectively. You ...

Problem There is a special kind of apple tree that grows apples every day for n days. On the iᵗʰ day, the tree grows apples[i...

Problem A company is organizing a meeting and has a list of n employees, waiting to be invited. They have arranged for a larg...

Problem Given a list of accounts where each element accounts[i] is a list of strings, where the first element accounts[i][0] ...

Problem In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for which all othe...

Problem You are given the root of a binary tree with unique values. In one operation, you can choose any two nodes at the sam...

Problem There is an exam room with n seats in a single row labeled from 0 to n - 1. When a student enters the room, they must...

Problem In this problem, a tree is an undirected graph that is connected and has no cycles. You are given a graph that starte...

Problem There is a strange printer with the following two special requirements: On each turn, the printer will print a solid...

Problem You are given a 0-indexed array heights of positive integers, where heights[i] represents the height of the iᵗʰ build...

Problem There is a strange printer with the following two special properties: The printer can only print a sequence of the s...

Problem The power of an integer x is defined as the number of steps needed to transform x into 1 using the following steps: ...

Problem You are given an array points, an integer angle, and your location, where location = [pos_x, pos_y] and points[i] = [...

Problem Given the root of a binary tree, return the postorder traversal of its nodes’ values. https://leetcode.com/probl...

Problem There is an undirected tree with n nodes labeled from 0 to n - 1. You are given the integer n and a 2D integer array ...

Problem Given an integer n, return all the structurally unique BST’s (binary search trees), which has exactly n nodes of uniq...

Problem There is a class with m students and n exams. You are given a 0-indexed m x n integer matrix score, where each row re...

Problem Given an integer n, return the number of structurally unique BST’s (binary search trees) which has exactly n nodes of...

Problem An n-bit gray code sequence is a sequence of 2ⁿ integers where: Every integer is in the inclusive range [0, 2ⁿ - 1],...

Problem Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2. You ha...

Problem Implement pow(x, n), which calculates x raised to the power n (i.e., xⁿ). https://leetcode.com/problems/powx-n/ Examp...

Problem Given an expression such as expression = "e + 8 - a + 5" and an evaluation map such as {"e": 1} (given in terms of ev...

Problem Given a string s which represents an expression, evaluate this expression and return its value. The integer division ...

Problem Given a string s representing a valid expression, implement a basic calculator to evaluate it, and return the result ...

Problem Given the root of a perfect binary tree, reverse the node values at each odd level of the tree. For example, suppose...