LeetCode_3Sum

 1 class Solution {

 2 public:

 3     vector<vector<int> > threeSum(vector<int> &num) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         vector<vector<int> > output; 

 7         if(num.size()<3) return output; 

 8          

 9         sort(num.begin(), num.end());

10         

11         for(int i =0; i< num.size() -2 ;){

12             int startS = i + 1 ;

13             int endS = num.size() - 1 ;

14             while(startS < endS){

15              

16              int sum = num[i] + num[startS] + num[endS];

17              if(sum == 0) {

18                     vector<int> triplet;  

19                     triplet.push_back(num[i]);  

20                     triplet.push_back(num[startS]);  

21                     triplet.push_back(num[endS]);  

22                     output.push_back(triplet);  

23                     startS++ ;

24                     while(num[startS] == num[startS-1] && startS < endS) startS++;

25              }

26              if(sum < 0)

27                    startS ++;

28              else

29                     endS --;    

30             }   

31             i++;

32             while(num[i] == num[i-1] && i< num.size() -2) i ++;     

33         }        

34         return output;

35     }

36 };

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和3Sum closest 类似，注意删除重复的三元组就行