Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This is c……
Given a string which contains only lowercase letters, remove duplicate letters so that every letter appear once and only once. You must make sure your result ……
Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1. Examples: s = "leetcode" return 0. ……
Given a string containing only digits, restore it by returning all possible valid IP address combinations. For example: Given "25525511135", return ["……
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example, "A man, a plan, a canal: Panam……
The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for bett……
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true……
Implement strStr(). Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. 题意：查找子串在主串……
Given two binary strings, return their sum (also a binary string). For example, a = "11" b = "1" Return "100". 题意：把两个二进制的字符串相加……
Write a function to find the longest common prefix string amongst an array of strings. 题意：求字符串数组的最长公共前缀。 思路：拿前……
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