soln.cpp

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> ans;
        if(nums.size() < 3) return ans;
        sort(nums.begin(), nums.end());
        for(int i = 0; i < nums.size() - 2; ++i)
        {
            if(i > 0 && nums[i] == nums[i - 1]) continue;
            int l = i + 1;
            int r = nums.size() - 1;
            while (l < r)
            {
                int s = nums[i] + nums[l] + nums[r];
                if (s == 0)
                {
                    ans.push_back({nums[i], nums[l], nums[r]});
                    while(l < r && nums[l] == nums[l + 1]) ++l;
                    while(l < r && nums[r] == nums[r - 1]) --r;
                    ++l;
                    --r;
                } else if (s < 0) ++l;
                else --r;
            }
        }
        return ans;
    }
};