摘要： 344. Reverse String Write a function that takes a string as input and returns the string reversed. 反转string字符串 java代码: 第二种解法，更加快速 java代码: 阅读全文

摘要： 461. Hamming Distance 求两个数之间的汉明距离，两个等长字符串之间的汉明距离是两个字符串对应位置的不同字符的个数。换句话说，它就是将一个字符串变换成另外一个字符串所需要替换的字符个数。这里将书转化为二进制然后比较相同位置不同的数有几个。 java代码: 第二种方法，x，y两个数可 阅读全文

摘要： 257. Binary Tree Paths Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: All root-to-leaf paths are: 阅读全文

摘要： 27. Remove Element Given an array and a value, remove all instances of that value in place and return the new length. Do not allocate extra space for 阅读全文

摘要： 441. Arranging Coins You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins. Given n, 阅读全文

摘要： 20. Valid Parentheses Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brack 阅读全文

摘要： 1. Two Sum Given an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each input wo 阅读全文

摘要： 7. Reverse Integer Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321 此题题意为反转一个整数个各个数字，比如123，翻转后为321 java代码: 但 阅读全文

摘要： 13. Roman to Integer Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 给定一个罗马数字s，( I<=s<=MMM 阅读全文

摘要： Excel Sheet Column Number Related to question Excel Sheet Column Title Given a column title as appear in an Excel sheet, return its corresponding colu 阅读全文