GNU'S Not Unix

Given a string, find the length of the longest substring without repeating characters.Examples:Given “abcabcbb”, the answer is “abc”, which the length is 3.Given “bbbbb”, the answer is “b”, with the le

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. 这里给出一种AC的动态规划解法：时间和空间复杂度O

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 better legibility)P A H N A P L S I I G

回文数的判定，不使用额外的空间 Determine whether an integer is a palindrome. Do this without extra space.思路：将一个整数逆转，判定和原来的数相不相等 注意负数一定不是回文数#define IMAX numeric_limits<int>::max()#define IMIN numeric_limits<int>::m

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.思路：先构造罗马与数字的映射，接着对给定的字符串从头开始进行最长匹配，最大为4，依次进行，匹配完成则乘以相应位的量级，时间复杂度为O(n)#include <algorithm>#incl

easy 21. Merge Two Sorted Lists Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. 思路：利用map映射，值->指针集合，然后按值从

IP聚合 Accepts: 138  Submissions: 293  Time Limit: 2000/1000 MS (Java/Others)  Memory Limit: 65536/65536 K (Java/Others) Problem Description当今世界，网络已经无处不在了，小度熊由于犯了错误，当上了度度公司的网络管理员，他手上有大量的 IP列表，小度熊想知道在

Binary Tree Zigzag Level Order Traversal My Submissions QuestionEditorial Solution Total Accepted: 60410 Total Submissions: 210160 Difficulty: Medium Given a binary tree, return the zigzag level or

Reorder List My Submissions QuestionEditorial Solution Total Accepted: 64392 Total Submissions: 281830 Difficulty: Medium Given a singly linked list L: L0→L1→…→Ln-1→Ln, reorder it to: L0→Ln→L1→Ln-

‘.’ 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: bool isMatch(cons

Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lin

-31. Next Permutation My Submissions QuestionEditorial Solution Total Accepted: 66747 Total Submissions: 250247 Difficulty: Medium Implement next permutation, which rearranges numbers into the lexico

-61. Rotate List My Submissions QuestionEditorial Solution Total Accepted: 69769 Total Submissions: 303483 Difficulty: Medium Given a list, rotate the list to the right by k places, where k is non-ne

-67. Add Binary My Submissions QuestionEditorial Solution Total Accepted: 85904 Total Submissions: 309911 Difficulty: Easy Given two binary strings, return their sum (also a binary string).For exampl

#include <algorithm>#include <iostream>#include <sstream>#include <fstream>#include <iomanip>#include <cstdlib>#include <cstring>#include <vector>#include <string>#include <bitset>#include <c

第一道题：求有删除情况的最长回文子串题目： 解题思路：这个题严格意义上来说，删除了字符就谈不上回文串了，既然有删除，那估计考察的不是回文串，而是其他的，但是这个东西又有回文串的特点，细想一下——那就是不连续的回文串，想到不连续，就容易使人想到最长公共子序列，把源字符串逆序之后对比两个字符串发现：我靠，这不就是求两个序列的最长公共子序列（好像跟回文串没多大关系）。

通过最近对于一些算法题的思考，越来越发现动态规划方法的在时间上高效性，往往该问题可以轻松的找到暴力破解的方法，其时间复杂度却不尽人意。下面来看看几个常见的动态规划思路的经典问题例一.有一段楼梯有10级台阶，规定每一步只能跨一级或两级，要登上第10级台阶有几种不同的走法?（腾讯电面题之一） 其状态转移方程为： f(n):表示n阶楼梯有多少种走法f(n):表示n阶楼梯有多少种走法f(n)=f

Gray Code My Submissions QuestionEditorial Solution Total Accepted: 60277 Total Submissions: 165212 Difficulty: Medium The gray code is a binary numeral system where two successive values differ in

Binary Tree Postorder Traversal My Submissions QuestionEditorial Solution Total Accepted: 97358 Total Submissions: 273744 Difficulty: Hard Given a binary tree, return the postorder traversal of its

f(j+1)为以下标j结尾的连续子序列最大乘积值（1） 状态转移方程如何表示呢： 这里我们知道A[j]可能为正数(或0)或负数，那么当A[j]为正数，期望前j个乘积为正数，若为负数，则期望前面的为负数。故我们需定义两个函数来确定我们的状态转移方程： fmax(j+1)=max(max(fmax(j)∗A[j],A[j]),fmin(j)∗A[j]) fmin(j+1)=min(min(fmin

class Solution {public: void reverseWords(string &s) { for(string::size_type ix=0;ix!=s.size();++ix) { if(s[ix]==' ') if(s[ix+1]==' '){

难度系数：easy/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * };

逆转单链表，比较简单，不细讲，扫描依次改变指针指向。class Solution {public: ListNode* reverseList(ListNode* head) { if(head==nullptr)return head; ListNode * tmp = head->next; ListNode *prenode = hea

/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class

Longest Common Prefix My Submissions Difficulty: Easy Write a function to find the longest common prefix string amongst an array of strings.难度：easy 思路：求解所有字符串的最长前缀 首先拿第一个字符串作为标准，从第一个字符串开始检测，如果其

思路：先保存两个整数的和，然后两层循环搞定 平均时间复杂度：O(n2)O(n^2) 还是time limit,期待更好的解法。。。。class Solution {public: vector<vector<int>> fourSum(vector<int>& nums, int target) { vector<vector<int> > result;

3Sum My Submissions QuestionEditorial Solution Total Accepted: 115154 Total Submissions: 612489 Difficulty: Medium Given an array S of n integers, are there elements a, b, c in S such that a + b +

Contains Duplicate My Submissions QuestionEditorial Solution Total Accepted: 88863 Total Submissions: 214375 Difficulty: Easy Given an array of integers, find if the array contains any duplicates.

–46. Permutations My Submissions QuestionEditorial Solution Total Accepted: 101087 Total Submissions: 280282 Difficulty: Medium Given a collection of distinct numbers, return all possible permutation

class Solution {public: vector<vector<int>> permute(vector<int>& nums) { //int n=nums.size(); vector<vector<int>> res; sort(nums.begin(),nums.end()); do{

Implement strStr() My Submissions QuestionEditorial Solution Total Accepted: 104556 Total Submissions: 420107 Difficulty: Easy Implement strStr().Returns the index of the first occurrence of needl

Swap Nodes in Pairs My Submissions QuestionEditorial Solution Total Accepted: 95230 Total Submissions: 270562 Difficulty: Easy Given a linked list, swap every two adjacent nodes and return its head

Remove Element My Submissions QuestionEditorial Solution Total Accepted: 115367 Total Submissions: 340963 Difficulty: Easy Given an array and a value, remove all instances of that value in place an

Same Tree My Submissions QuestionEditorial Solution Total Accepted: 126116 Total Submissions: 291884 Difficulty: Easy Given two binary trees, write a function to check if they are equal or not.Two

Invert Binary Tree My Submissions QuestionEditorial Solution Total Accepted: 87818 Total Submissions: 193396 Difficulty: Easy Invert a binary tree.4 / \ 2 7 / \ / \ 1 3 6 9 to 4

Majority Element My Submissions QuestionEditorial Solution Total Accepted: 110538 Total Submissions: 268290 Difficulty: Easy Given an array of size n, find the majority element. The majority elemen

Remove Duplicates from Sorted Array My Submissions QuestionEditorial Solution Total Accepted: 127836 Total Submissions: 381794 Difficulty: Easy Given a sorted array, remove the duplicates in place

3Sum Closest My Submissions QuestionEditorial Solution Total Accepted: 76185 Total Submissions: 262100 Difficulty: Medium Given an array S of n integers, find three integers in S such that the sum

Climbing Stairs My Submissions QuestionEditorial Solution Total Accepted: 106498 Total Submissions: 290003 Difficulty: Easy You are climbing a stair case. It takes n steps to reach to the top.Each

Remove Nth Node From End of List My Submissions QuestionEditorial Solution Total Accepted: 106592 Total Submissions: 361392 Difficulty: Easy Given a linked list, remove the nth node from the end of