class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        sort(nums.begin(), nums.end());
        for(int i=0;i<nums.size();i++){
            if(i > 0 && nums[i]==nums[i-1]) continue;
            int l = i + 1;
            int r = nums.size() - 1;
            while(l < r){
                int s = nums[i] + nums[l] + nums[r];
                if(s < 0) l++;
                else if(s > 0) r--;
                else{
                    res.push_back({nums[i],nums[l],nums[r]}); //这个vector的操作很关键
                    while(l < r && nums[l] == nums[l+1]) l++;
                    while(l < r && nums[r] == nums[r-1]) r--;
                    l++;r--;
                }
                
            }
        }
        return res;
    }
};