# [15\. 3Sum](https://leetcode.com/problems/3sum/)

:::spoiler Solution

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

- T: $O(N^2)$
- S: $O(\log N)$
:::