Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example,If n = 4 and k = 2, a solution is: [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ] 思路:有点像0-1背包问题, 对于从1-n的每一个数字都可以选择放入答案 和不放入答案. 当长度达到k时就是一个符合条件的解. 递归的…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 使用哑结点 不使用哑结点 日期 题目地址:https://leetcode.com/problems/middle-of-the-linked-list/description/ 题目描述 Given a non-empty, singly linked list with head node head, return a middle node o…

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example,If n = 4 and k = 2, a solution is: [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ] class Solution { public: vector<vector<int> > combine(int n,…

Given a collection of numbers, return all possible permutations. For example,[1,2,3] have the following permutations:[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1]. 求没有重复数字的全排列 思路:用的标准回溯法,一次AC class Solution { public: vector<vector<int>…

Given an array of strings, return all groups of strings that are anagrams. Note: All inputs will be in lower-case. anagrams 的意思是两个词用相同的字母组成  比如 “dog" "god" 思路: 把单词排序 如 dog 按字母排序变为 dgo 用unordered_map<string, int> 记录排序后序列第一次出现时,字符串在输入st…

[LeetCode]518. Coin Change 2 解题报告(Python) 作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 题目地址:https://leetcode.com/problems/coin-change-2/description/ 题目描述: You are given coins of different denominations and a total amount of money. Write a…

[LeetCode]Minimum Depth of Binary Tree Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. 递归和非递归,此提比较简单.广度优先遍历即可.关键之处就在于如何保持访问深度. 下面是4种代码: im…

Given an index k, return the kth row of the Pascal's triangle. For example, given k = 3, Return [1,3,3,1]. Note: Could you optimize your algorithm to use only O(k) extra space? 思路:最简单的方法就是依照[Leetcode]Pascal's Triangle 的方式自顶向下依次求解,但会造成空间的浪费.若仅仅用一个vect…

53. Maximum Subarray[leetcode] Find the contiguous subarray within an array (containing at least one number) which has the largest sum. For example, given the array [-2,1,-3,4,-1,2,1,-5,4],the contiguous subarray [4,-1,2,1] has the largest sum = 6. 挑…

27. Remove Element[leetcode] Given an array and a value, remove all instances of that value in place and return the new length. Do not allocate extra space for another array, you must do this in place with constant memory. The order of elements can b…