题目: 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], ] 代码: class Solution { public: vector<vector<int>> combine…

题目: 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]. 代码: class Solution { public: vector<vector<int>> permute(vector&…

题目: Given a set of distinct integers, nums, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If nums = [1,2,3], a solution is: [ [3], [1], [2], […

题目: Given an array of strings, return all groups of strings that are anagrams. Note: All inputs will be in lower-case. 代码: class Solution { public: vector<string> anagrams(vector<string>& strs) { vector<string> ret; map<string,vec…

题意: 给出一个2*n的方格,当刷完某一个方格的漆后可以且只可以走到相邻的任何一格,即上 下 左 右 左上 左下 右上 右下.可以从任意一个格子开始刷墙,问有多少种刷法,因为随着n的增大方案数会变多,因此输出方案数mod 1000000007. 思路: dp[][2], dp[i][0]表示2*i的格子从第i列开始刷,最后回到该格子下面   dp[i][1]表示2*i的格子从第i列开始刷,最后无法回到该格子下面 状态转移方程是:dp[i][0] = 2*dp[i-1][0] 即 A1->B1->…

题目: Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below. For example, given the following triangle [ [], [,4], [6,,7], [4,,8,3] ] The minimum path sum from top to bottom is 11 (i…

题目: The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all distinct solutions to the n-queens puzzle. Each solution contains a distinct board configuration…

题目: There are N children standing in a line. Each child is assigned a rating value. You are giving candies to these children subjected to the following requirements: Each child must have at least one candy. Children with a higher rating get more cand…

题目: 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. Note: Elements in a quadruplet (a,b,c,d) must be in non-descending or…

题目: Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The s…