15

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        int left, right, sum;
        vector<vector<int>> res;
        for(int i=0; i<nums.size(); i++){
            if(i > 0 && nums[i] == nums[i-1]) continue;
            sum = -nums[i];
            left = i+1;
            right = nums.size()-1;
            while(left < right){
                if(nums[left]+nums[right] > sum) right--;
                else if(nums[left]+nums[right] < sum) left++;
                else if(nums[left]+nums[right] == sum){
                    res.push_back({nums[i], nums[left], nums[right]});
                    while(left < nums.size()-1 && nums[left] == nums[left+1]) left++;
                    while(right > i && nums[right] == nums[right-1]) right--;
                    left++;
                    right--;
                }
            }
        }
        return res;
    }
};