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

void find(string& input, string cur, int pos, vector<string>&subset)
{
  if (cur.length())
    subset.push_back(cur);
  if (pos == input.size())
    return;
  for(int i = pos; i < input.length(); i++)
  {
    cur.push_back(input[i]);
    find(input, cur, i+1, subset);
    cur.pop_back();
  }
}

vector<string> find_all_subset(string input)
{
  vector<string> subset;
  find(input, "", 0, subset);
  return subset;
}

int main()
{
  string input = "abcd";
  vector<string> result = find_all_subset(input);
  for (int i =0; i <result.size(); i++)
    cout<<result[i]<< ", "<<endl;
  return 1;
}