import java.util.Collections;
import java.util.ArrayList;

/**
  This program tests the subset generator.
*/
public class SubsetGeneratorTester
{
  public static void main(String[] args)
  {
     SubsetGenerator generator
           = new SubsetGenerator("rum");
     
     ArrayList<String> subsets = generator.getSubsets();
     // Sort the result for checking
     Collections.sort(subsets);
     System.out.println(subsets);
     System.out.println("Expected: [, m, r, rm, ru, rum, u, um]");
  }
}

import java.util.ArrayList;

/**
  This class generates subsets of a string.
*/
public class SubsetGenerator
{
  /**
     Constructs a subset generator.
     @param aWord the word to obtain subsets from
  */
  ....

  public ArrayList<String> getSubsets()
  {
     ....

     // Form a simpler word by removing the first character
     ....

     // Generate all subsets of the simpler word
     ....

     // Add the removed character to the front of
     // each subset of the simpler word, and
     // also include the word without the removed character
     ....
     
     // Return all subsets
     ....
  }

  ....
}

import java.util.Collections;
import java.util.ArrayList;

/**
  This program tests the subset generator.
*/
public class SubsetGeneratorTester
{
  public static void main(String[] args)
  {
     SubsetGenerator generator
           = new SubsetGenerator("rum");
     
     String subsets = generator.nextGen();
     // Sort the result for checking
     System.out.println(subsets);
     System.out.println("Expected: [, m, r, rm, ru, rum, u, um]");
  }
}

import java.util.*;
import java.io.*;
 
public class SubsetGenerator
{
 
    private String subset;
    private int current;
    private SubsetGenerator tailGenerator;
    boolean addedFirst;
 
    public SubsetGenerator(String aSubset)
    {        
     subset = aSubset;
     addedFirst = subset.length() == 0;
        if (subset.length() > 0)
           tailGenerator = new SubsetGenerator(subset.substring(1));
    }
   
    public String nextGen()
    {
        if (subset.length() == 1)
        {
            current++;
            return subset;
        }
 
        String r = subset.charAt(current) + tailGenerator.nextGen();
       
        if (!tailGenerator.SubsetGen())
        {
            current++;
            if (current < subset.length())
            {
                String tailString = subset.substring(0, current)
                       + subset.substring(current + 1);
                tailGenerator = new SubsetGenerator(tailString);
            }
            return r;
        }
       
        return "none";
    }
 
    public boolean SubsetGen()
    {
        return addedFirst || tailGenerator != null && tailGenerator.SubsetGen();
    }
 
}

def subsets_helper(input_str, lst):
 if len(input_str) == 0:
   return lst

 if input_str not in lst:
   lst.append(input_str)
 for i in range(len(input_str)):
   subsets_helper(input_str[0:i] + input_str[i+1:len(input_str)], lst)
 return lst

def subsets(input_str):
 return subsets_helper(input_str, [''])


print h('rum')

   public class SubsetGenerator {

       private String text;

       public SubsetGenerator(String text) {
           this.text = text;
       }

       public ArrayList<String> getSubsets() {
           return getSubsets(text);
       }

       private ArrayList<String> getSubsets(String word) {
           ArrayList<String> subsets = new ArrayList<String>();

           if (word.equals("")) {
               subsets.add("");
               return subsets;
           }

           String firstLetter = word.substring(0, 1);
           String simplerWord = word.substring(1);

           for (String simplerSubset : getSubsets(simplerWord)) {
               subsets.add(firstLetter + simplerSubset);
               subsets.add(simplerSubset);
           }

           return subsets;
       }
   }