LeetCode Subsets

核心就是求组和，求所有的组合，要求每个子集按序，所以要排序，但是不能再递归里对原来的数组排序，这样会破坏递归结构，所以要用一个临时变量解决。

void addSubsets(vector<int> &S,int n,int i,int k,vector<int> &res,vector<vector<int> >&ret)
{
	if(k==0)
	{
		vector<int> temp(res);
		sort(temp.begin(),temp.end());
		ret.push_back(temp);
		return;
	}
	if(i==n)
		return;
	res.push_back(S[i]);
	addSubsets(S,n,i+1,k-1,res,ret);
	res.pop_back();
	addSubsets(S,n,i+1,k,res,ret);
}

vector<vector<int> > subsets(vector<int> &S) {
	vector<vector<int> > ret;
	vector<int> res;
	ret.push_back(res);
	int lenS = S.size();
	
	for (int k=1;k<lenS;k++)
	{
		res.clear();
		addSubsets(S,lenS,0,k,res,ret);
	}
	if(lenS!=0)
	{
		sort(S.begin(),S.end());
		ret.push_back(S);
	}
	return ret;
}

int _tmain(int argc, _TCHAR* argv[])
{
	vector<vector<int> >ret;
	//ret = combine(5,3);
	vector<int> S;
	S.push_back(4);
	//S.push_back(3);
	S.push_back(1);
	S.push_back(0);
	ret = subsets(S);
	vector<vector<int> >::iterator iter1=ret.begin();
	vector<int>::iterator iter2;
	while(iter1!=ret.end())
	{
		iter2 = iter1->begin();
		while(iter2!=iter1->end())
		{
			cout<<*iter2<<" ";
			iter2++;
		}
		cout<<endl;
		iter1++;
	}
	system("pause");
	return 0;
}