标签：ret duplicate bsp return ++ blog hat log note
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: 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] ]
利用3sum的思想，还是比较简单的
1 class Solution { 2 public: 3 vector<vector<int>> fourSum(vector<int>& nums, int target) { 4 sort(nums.begin(),nums.end()); 5 vector<int> temp; 6 vector<vector<int>> res; 7 //利用3sum 8 int target3,target2; 9 for(int i=0;i<nums.size();i++) 10 { 11 target3=target-nums[i]; 12 for(int j=i+1;j<nums.size();j++) 13 { 14 int front=j+1,back=nums.size()-1; 15 target2=target3-nums[j]; 16 while(front<back) 17 { 18 if(nums[front]+nums[back]<target2) front++; 19 else if(nums[front]+nums[back]>target2) back--; 20 else 21 { 22 temp.push_back(nums[i]); 23 temp.push_back(nums[j]); 24 temp.push_back(nums[front]); 25 temp.push_back(nums[back]); 26 res.push_back(temp); 27 while(nums[front]==temp[2]) front++; 28 while(nums[back]==temp[3]) back--; 29 temp.clear(); 30 } 31 } 32 while(j+1<nums.size()&&nums[j]==nums[j+1]) j++; 33 } 34 while(i+1<nums.size()&&nums[i]==nums[i+1]) i++; 35 } 36 return res; 37 } 38 };
标签：ret duplicate bsp return ++ blog hat log note
原文地址：http://www.cnblogs.com/wsw-seu/p/7627021.html
