class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {

        sort(nums.begin(), nums.end());
        unordered_map<int,int> M;
        vector<vector<int> > res;
        for(int i = 0; i < nums.size(); i++) {
            M[nums[i]] = i;
        }

        for(int i = 0; i < nums.size(); i++) {
            if(i != 0 && nums[i] == nums[i - 1]) continue;
            int need = -nums[i];
            for(int j = i + 1; j < nums.size(); j++) {
                if(j != i + 1 && nums[j] == nums[j - 1]) continue;
                int req = need - nums[j];
                 if(req > nums[nums.size() - 1]) continue;

                if(M.count(req) && M[req] > j) {
                    res.push_back({nums[i],  nums[j], req});
                }
            }
        }

        return res;

    }
};