题目描述:4Sum
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 order. (ie, a ≤ b ≤ c ≤ d)
- The solution set must not contain duplicate quadruplets.
For example, given array S = {1 0 -1 0 -2 2}, and target = 0. A solution set is: (-1, 0, 0, 1) (-2, -1, 1, 2) (-2, 0, 0, 2)
代码如下:
class Solution { public: vector<vector<int> > fourSum(vector<int> &num, int target) { // Note: The Solution object is instantiated only once. vector<vector<int>> res; int numlen = num.size(); if(num.size()<4) return res; sort(num.begin(),num.end()); set<vector<int>> tmpres; for(int i = 0; i < numlen; i++){ for(int j = i + 1; j < numlen; j++){ int begin = j+1; int end = numlen-1; while(begin < end){ int sum = num[i]+ num[j] + num[begin] + num[end]; if(sum == target){ vector<int> tmp; tmp.push_back(num[i]); tmp.push_back(num[j]); tmp.push_back(num[begin]); tmp.push_back(num[end]); tmpres.insert(tmp); begin++; end--; } else if(sum<target) begin++; else end--; } } } set<vector<int>>::iterator it = tmpres.begin(); for(; it != tmpres.end(); it++) res.push_back(*it); return res; } };
时间: 2024-10-24 12:20:53