18 4Sum((寻找四个数之和为指定数的集合Medium))

 1 class Solution {
 2 public:
 3     vector<vector<int>> fourSum(vector<int>& nums, int target) {
 4         vector<vector<int>> ans;
 5         vector<int> vec(4);
 6         int k,l,temp;
 7         sort(nums.begin(),nums.end());
 8         for(int i=0;i<nums.size();++i){
 9             if(i>0&&nums[i]==nums[i-1])continue;
10             for(int j=i+1;j<nums.size();++j){
11                 if(j>i+1&&nums[j]==nums[j-1])continue;
12                     k=j+1;
13                     l=nums.size()-1;
14                     while(k<l){
15                         if(k>j+1&&nums[k]==nums[k-1]){
16                             ++k;
17                             continue;
18                         }
19                         temp=nums[i]+nums[j]+nums[k]+nums[l];
20                         if(temp>target)--l;
21                         else if(temp<target)++k;
22                         else{
23                             vec[0]=nums[i];
24                             vec[1]=nums[j];
25                             vec[2]=nums[k];
26                             vec[3]=nums[l];
27                             ans.push_back(vec);
28                             --l;
29                             ++k;
30                         } 
31                     }
32             }
33         }
34         return ans;
35     }
36 };