#include<iostream>
using namespace std;
class solution{
public:
	std::vector<std::vector<int> > threesum(std::vector<int> &num){
		std::vector<char> ret;
		if (num.size()<=2)
		{
			/* code */
			return ret;
		}
		sort(num.begin(),num.end());
		for (int i = 0; i < num.size()-2; ++i)
		{
			int j=i+1;
			int k=num.size()-1;
			while (j<k)
			{
				if(num[i]+num[j]+num[k]==0)
				{
					ret.push_back(num[i]);
					ret.push_back(num[j]);
					ret.push_back(num[k]);
					j++;
					k--;
				
				while(j<k&&num[j]==num[j-1])

				{
					j++;
					/* code */
				}
				while (j<k&&num[k]==num[k-1])
				{
					k--;
				}
			    }
			    if(num[i]+num[j]+num[k]<0)
			    {
			    	j++;
			    }
			    else
			    {
			    	k++;				  
			    }
			    while(i<num.size()-1&&num[i]==num[i+1])
			    {
			    	i++;
			    }
			}
			/* code */
		}
	}
}