Leetcode 15. 三数之和

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        int n = nums.size();
        // if(n < 3)
        // {
        //     return res;
        // }
        sort(nums.begin(),nums.end());
        for(int i = 0;i < n-2 ;i++)
        {
            if(nums[i] > 0)
            {
                return res;
            }
            if(i > 0 && nums[i] == nums[i-1])
            {
                continue;
            }
            int left = i+1;
            int right = n-1;
            while(left < right)
            {
                int sum = nums[i] + nums[left] + nums[right];
                if(sum == 0)
                {
                    res.push_back({nums[i], nums[left], nums[right]});
                    
                    while(right > left && nums[right] == nums[right-1])
                    {
                        right--;
                    }
                    while(left < right && nums[left] == nums[left + 1])
                    {
                        left++;
                    }
                    right--;
                    left++;
                }
                else if (sum < 0)
                {
                    left++;
                }
                else
                {
                    right--;
                }
            }
        }
        return res;
    }
};

双指针解法