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Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a

Given an absolute path for a file (Unix-style), simplify it.For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c"Corner Cases:Did you consider the case where p

Given an array of strings, group anagrams together.For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], Return:[ ["ate", "eat","tea"], ["nat","tan"], ["bat"]]Note: Al

The count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1 is read off as "one 1" or 11.11 is read off as "two 1s" or 21.21 is read off as 

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.题意把罗马数字转变为int型数据题解转变的规则      ：//Ⅰ（1）Ⅴ（5）Ⅹ（10）L（50）C（100）D（500）M（1000） 

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.题意把int型数据转换为罗马数字。题解根据罗马的转换制度由高到低转换即可      const int radix[] =

Validate if a given string is numeric.Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => trueNote: It is intended for the problem statement to be ambiguo

Write a function to find the longest common prefix string amongst an array of strings.题意找字符串数组里的最长公共前缀。题解解法很多，第一个是横向匹配，第一组与每一组对比，每比一次取最小公共前缀。匹配完则得到所有公共前缀。能通过，但是比较慢class Solution {public:

Implement wildcard pattern matching with support for '?' and '*'.'?' Matches any single character.'*' Matches any sequence of characters (including the empty sequence).The matching should cover t

Implement regular expression matching with support for '.' and '*'.'.' Matches any single character.'*' Matches zero or more of the preceding element.The matching should cover the entire input st

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.题意找S中的最长回文子串，回

Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".题意两个字符串表示两个二进制数，返回二进制的字符串表示他们的和。题解我是先翻转再操作，这样可以从下标0开始操作。注意长度，以及最后进位。

Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input ca

Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.题意两个字符串haystack和needle ，如果needle是haystack的子串，返回needle在haystack

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.If the last word does not exist, return 0.Note: A word is