给定一个整数数组和一个目标值，找出数组中和为目标值的两个数。 你可以假设每个输入只对应一种答案，且同样的元素不能被重复利用。 示例: 给定 nums = [2, 7, 11, 15], target = 9 因为 num…

在未排序的数组中找到第 k 个最大的元素。请注意，你需要找的是数组排序后的第 k 个最大的元素，而不是第 k 个不同的元素。 输入: [3,2,1,5,6,4] 和 k = 2 输出: 5 输入: [3,2,3,1,2,…

Given a string containing only digits, restore it by returning all possible valid IP address combinations. For…

方法很牛逼也很数学。没做的时候可能想不到。做了之后就觉得，哎，我去，有道理啊。 简而言之：简历一个boolean长条，存isPrime[]。 然后从i=2， 全部变true. 然后利用这个因子的性质，非prime满足条件…

Problem You are climbing a stair case. It takes n steps to reach to the top. Each time you can either climb 1 …

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Given a linked list, swap every two adjacent nodes and return its head. For example, Given 1->2->3-…

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题目： Given an array of non-negative integers, you are initially positioned at the first index of the array. Eac…