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题目描述： Given a string, find the length of the longest substring without repeating characters.

题目描述： A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time.

题目描述： Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)

题目描述： Given a binary tree, return the level order traversal of its nodes’ values.

题目描述： There are N children standing in a line. Each child is assigned a rating value. What is the minimum candies you must give?

题目描述： There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expresse

题目描述： Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position.

题目描述： Given two integers n and k, return all possible combinations of k numbers out of 1 … n

题目描述： You are given coins of different denominations and a total amount of money amount. Write a function to compute the fewest number of coins that you need to make up that amount. If that amount of