Solution.cpp

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