class Solution {
public:

vector<vector<int> > threeSum(vector<int> &num) 
	{
		vector<vector<int> > res;
		sort(num.begin(), num.end());
 
		for (int i = 0; i < num.size(); i++)
		{
            const int& a = num[i];
			//if (a > 0) break; // save the loop times!
			for (int j = i+1, k = num.size()-1; j < k; )
			{
				if (a+num[j]+num[k] < 0) j++;
				else if (a+num[j]+num[k] >0) k--;
				else
				{
					res.push_back({a,num[j],num[k]});
					j++, k--;
					while (j<k && num[j] == num[j-1]) j++;
					while (j<k && num[k] == num[k+1]) k--;
				}
			}
			while (i<num.size() && a == num[i+1]) i++;
		} 
		return res;
}

};