부분집합

vector<int> v;
vector<char> select;
void back(bool sel)
{
 if(select.size() == v.size())
 {
  for(int i=0; i<v.size(); i++)
  {
   if(select[i] == true)
    cout << v[i] << ", ";
  }
  cout << endl;
 }
 else
 {
  select.push_back(true);
  back(true);
  select.pop_back();

  select.push_back(false);
  back(false);
  select.pop_back();
 }
}
int main()
{
 int arr[] = {1,2,3};
 v.assign(arr, arr+3);

 back(0);
 return 0;
}