幂集问题 子集问题

#include <iostream>
#include <vector>
using namespace std;

vector<vector<int> > ps;

//为vector<int> 重载输出运算符
//一层层来。
ostream &operator <<(ostream &os, vector<int> vec)
{
    vector<int>::iterator ittt = vec.begin();
    for (;ittt != vec.end(); ++ittt)
    {
        os << *ittt;
    }
    return os;
}

// 幂集问题
vector<vector<int> > subSet(int n)
{
    
    vector<vector<int> > ps1;
    vector<int> s;
    vector<vector<int>>::iterator it; 
    ps.push_back(s);

    for (int i = 1; i <= n; i++)
    {
        ps1=ps;

        for (it = ps1.begin(); it != ps1.end(); it++)
        {
            (*it).push_back(i);
        }
        for (it = ps1.begin(); it != ps1.end(); it++)
        {
            ps.push_back(*it);
        }
    }
    return ps;

}


int main()
{

    
    int n;
    cin >> n;
     
    subSet(n);
    vector<vector<int> >::iterator itt;
    cout << "子集为:";
    for (itt = ps.begin(); itt != ps.end(); itt++)

    {
        cout << *itt << ",";
    }

    cout <<endl;
    cout<< "子集个数：";
    cout << ps.size();

}