Given a linked list, remove the nth node from the end of list and return its head. For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list becomes 1->2->3->5. Note: Given…

题目描述:Remove Nth Node From End of List Given a linked list, remove the nth node from the end of list and return its head. For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked list bec…

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. 解题思路一: 暴力枚举 共N^2量级个子串(从下标零开始),每次检查需一个for循环,等于是3重for循环,时间复杂度O(n^3) 解题思路二: 动态…

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest subst…

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list. Input: (2 -> 4 -> 3) + (5 -> 6 ->…

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses. For example, given n = 3, a solution set is: "((()))", "(()())", "(())()", "()(())", "()()()" 解题思路一:…

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. 解题思路一: 四路夹逼,C++: class Solution { public: vector<vector<int> > fou…

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 string (not partial). The function prototype should be…

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 cases. Notes: It is intended for this problem to be spe…

Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 解题思路:将数字翻转并不难,可以转成String类型翻转,也可以逐位翻转,本题涉及到的主要是边界和溢出问题,使用Long或者BigInteger即可解决. 题目不难: JAVA实现如下: public class Solution { static public int reverse(int x) { if(x=…