题目：
Given an array of integers, every element appears twice except for one. Find that single one.Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?
思路：
要求线性时间完成，并且不使用额外的存储空间。**非常之巧妙**
使用异或来排除double值，剩下的就是single one. 异或具有可交换性，顺序可变。
比如给出数组{2,1,4,5,2,4,1} ，求异或，2^1^4^5^...
N皇后问题源于著名的八皇后问题：在8×8格的国际象棋上摆放八个皇后，使其不能互相攻击，即任意两个皇后都不能处于同一行、同一列或同一斜线上，问有多少种摆法！将8x8扩展为NxN即为N皇后问题，要解决此问题，最简单的方法就是暴力枚举，此时的时间复杂度为N^2，回溯算法与简单暴力枚举类似，不同点在于当判定某种状态不符合答案时，便不再继续枚举此状态的后续状态，而是回溯到该状态之前，继续遍历其他的可能值。 1 #include <ios...
题目：Given two words (beginWord and endWord), and a dictionary‘s word list, find all shortest transformation sequence(s) from beginWord to endWord, such that:Only one letter can be changed at a timeEach transformed word must exist in the word list. Note that beginWord is not a transformed word.Note:Return an empty list if there is no such transformation sequence.All words have the same length.Al...
题目：
Given a list, rotate the list to the right by k places, where k is non-negative.
For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.
给出一个链表，和一个非负数k, 要求从链表尾节点开始计数，k步进行旋转，得到新的链表。Given [0,1,2], rotate 1 steps to the right -> [2,0,1].
Given [0,1,2], rotate 2 steps to the right -> [1,2,0].
Given [0,1,2], rotate 3 steps to the right...
指数：[LeetCode] Leetcode 解决问题的指数 (C++/Java/Python/Sql)
Github: https://github.com/illuz/leetcode033. Search in Rotated Sorted Array (Hard)链接：题目：https://leetcode.com/problems/search-in-rotated-sorted-array/
代码(github)：https://github.com/illuz/leetcode题意：在一个旋转过的有序数组中找一个数。
比方 4 5 6 7 0 1 2 就是一个“旋转过的有序数组”。分析：这是单纯二分搜索的变形。
由于旋转过不...
题目：
Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end, such that:Only one letter can be changed at a timeEach intermediate word must exist in the dictionary
For example,
Given:start = "hit"end = "cog"dict = ["hot","dot","dog","lot","log"]
As one shortest transformation is "hit" -> "hot" -> "dot" -> "dog" -> "cog",
return its...
题目：You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way.The null node needs to be represented by empty parenthesis pair "()". And you need to omit all the empty parenthesis pairs that don‘t affect the one-to-one mapping relationship between the string and the original binary tree.Example 1:Input: Binary tree: [1,2,3,4]1/ ...
class Solution {
public:vector<int> findDisappearedNumbers(vector<int>& nums) {vector<int> res;int m;for(int i=0;i<nums.size();i++){m = abs(nums[i]) - 1;if(nums[m] > 0){nums[m] *= -1;}}for(int i=0;i<nums.size();i++){if(nums[i] > 0){res.push_back(i+1);}}return res;}
};
原文：https://www.cnblogs.com/theodoric008/p/9443880.html
Given an integer (signed 32 bits), write a function to check whether it is a power of 4.Example:Given num = 16, return true. Given num = 5, return false.个人博客：http://www.cnblogs.com/wdfwolf3/这道题本身没有难度，这里只是介绍两种思路，当我们判断出它二进制只有1个1的时候，即必为2的幂时，如何进一步判断它是不是4的幂。1. 8msclass Solution {
public:bool isPowerOfFour(int num) {if(num<=0)returnfalse;i...
Problem:
Given an array and a value, remove all instances of that value in place and return the new length.
The order of elements can be changed. It doesn‘t matter what you leave beyond the new length.Solution:和26题一样，就是判断条件不一样而已。题目大意：给一个数组，要求返回删除所有指定元素的数组。好鸡冻，第一次全部通过，没有一个错误（虽然题目比较简单）。。。。。。贴图留念：Java源代码（248ms）：...
1.题目大意Given an array nums, write a function to move all 0‘s to the end of it while maintaining the relative order of the non-zero elements.For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].Note:You must do this in-place without making a copy of the array.Minimize the total number of operations.解析：给定一个组的数字，把所有0都移到数组的末...
题目：Print a binary tree in an m*n 2D string array following these rules:The row number m should be equal to the height of the given binary tree.The column number n should always be an odd number.The root node‘s value (in string format) should be put in the exactly middle of the first row it can be put. The column and the row where the root node belongs will separate the rest space into two part...
索引：[LeetCode] Leetcode 题解索引 (C++/Java/Python/Sql)
Github: https://github.com/illuz/leetcode032. Longest Valid Parentheses (Hard)链接：题目：https://oj.leetcode.com/problems/longest-valid-parentheses/
代码(github)：https://github.com/illuz/leetcode题意：问一个字符串里最长的合法括号串的长度。分析：(C++)用栈来做，如果匹配就出栈，然后长度就是 cur - stack_top_pos 也就是 - 匹配的前一个位置。 O(n...
题目描述：你现在是棒球比赛记录员。给定一个字符串列表，每个字符串可以是以下四种类型之一：1.整数（一轮的得分）：直接表示您在本轮中获得的积分数。2. "+"（一轮的得分）：表示本轮获得的得分是前两轮有效 回合得分的总和。3. "D"（一轮的得分）：表示本轮获得的得分是前一轮有效 回合得分的两倍。4. "C"（一个操作，这不是一个回合的分数）：表示您获得的最后一个有效 回合的分数是无效的，应该被移除。每一轮的操作都是永久性...
1. 题目1.1 英文题目Given two binary strings a and b, return their sum as a binary string.1.2 中文题目给定两个二进制字符串，返回他们的和（用二进制表示）。输入为非空字符串且只包含数字 1 和 0。1.3输入输出输入输出a = "11", b = "1""100"a = "1010", b = "1011""10101"1.4 约束条件1 <= a.length, b.length <= 104a and b consist only of ‘0‘ or ‘1‘ characters.Each string does not contain leading zeros excep...
题目：