leetcode 15.三数之和

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


        }
        return ans;
    }
};