刷题记录0502

题目描述：15.三数之和

代码：

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        int n=nums.size();
        vector<vector<int>> res;
        sort(nums.begin(),nums.end());
        for(int first=0;first<n;++first){
            if(first>0&&nums[first]==nums[first-1]){
                continue;
            }
            int third=n-1;
            for(int second=first+1;second<n;++second){
                if(second>first+1&&nums[second]==nums[second-1]){
                    continue;
                } 
                while(second<third&&nums[first]+nums[second]+nums[third]>0){
                    third--;
                }
                if(second==third){
                    break;
                }
                if(nums[first]+nums[second]+nums[third]==0){  
                res.push_back({nums[first],nums[second],nums[third]});
                }
            }
        }
        return res;
    }
};

思路：