LeetCode_3Sum

class Solution {
public:
    vector<vector<int> > threeSum(vector<int> &num) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<vector<int> > output; 
        if(num.size()<3) return output; 
         
        sort(num.begin(), num.end());
        
        for(int i =0; i< num.size() -2 ;){
            int startS = i + 1 ;
            int endS = num.size() - 1 ;
            while(startS < endS){
             
             int sum = num[i] + num[startS] + num[endS];
             if(sum == 0) {
                    vector<int> triplet;  
                    triplet.push_back(num[i]);  
                    triplet.push_back(num[startS]);  
                    triplet.push_back(num[endS]);  
                    output.push_back(triplet);  
                    startS++ ;
                    while(num[startS] == num[startS-1] && startS < endS) startS++;
             }
             if(sum < 0)
                   startS ++;
             else
                    endS --;    
            }   
            i++;
            while(num[i] == num[i-1] && i< num.size() -2) i ++;     
        }        
        return output;
    }
};

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和3Sum closest 类似，注意删除重复的三元组就行