15_3Sum.cpp

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