1 class Solution { 2 public: 3     vector<vector<int> > threeSum(vector<int> &num) { 4         vector<vector<int> > res; 5         sort(num.begin(),num.end()); 6         int n = num.size(); 7         for(int i = 0 ; i < n-2 ; ++i){ 8             if(i > 0 && (num[i] == num[i-1])){ 9                 continue;10             }11             int target = -num[i];12             int left = i+1;13             int right = n-1;14             while(left < right){15                 if(target == num[left] + num[right]){16                     vector<int> triplet;17                     triplet.push_back(num[i]);18                     triplet.push_back(num[left]);19                     triplet.push_back(num[right]);20                     res.push_back(triplet);21                     left++;22                     while((left < right) && (num[left] == num[left-1])){23                         left++;24                     }25                     right--;26                     while((right > left) && (num[right] == num[right+1])){27                         right--;28                     }29                 }30                 else if(target > num[left] + num[right]){31                     left++;32                     while((left < right) && (num[left] == num[left-1])){33                         left++;34                     }35                 }36                 else{37                     right--;38                     while((right > left) && (num[right] == num[right+1])){39                         right--;40                     }41                 }42             }43         }44         return res;45     }46 };