Question

现在我的程序输出[m，r，rm，ru，rum，u，um]，由于某种原因递归方法不输出rm答案。我一直跟踪它，但我似乎无法正确追踪它并找到问题所在。我不确定丢失的子集在哪里？谢谢！

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/**
   Prints subsets of String
*/

public class SubsetGenerator
{
    private String word="";

    private ArrayList<String> subsets;

    /**
        Constructs a word to generate subsets from
        @param text input by user
    */
    public SubsetGenerator(String textinput)
    {
        word=textinput;
        subsets = new ArrayList<String>();
    }



    /**
        retrieves word
        @return the word
    */
    public String getWord()
    {
        return word;
    }




    /**
        get subsets
        @return subset arraylist
    */
    public ArrayList<String> getSubsets()
    {
         if(word.length()==0)
         {
             subsets.add("");
             return subsets;
         }
         else
         {
             String removed=word.substring(0,1);
             word=word.substring(1);
             subsets.add(removed);

             for(int i=0;i<word.length();i++)
             {
                String temp=removed+word.substring(0,i+1);
                subsets.add(temp);
             }
         }

         getSubsets();
         return subsets;
   }
}



/**
   This program tests the subset generator.
*/
public class SubsetGeneratorTester
{
   public static void main(String[] args)
   {
      SubsetGenerator generator = new SubsetGenerator("rum");

      List<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]");
   }
}

Answer 1

如果你想抓住word.substring()，你还需要沿着rm的起点进行迭代。

public ArrayList<String> getSubsets()
{
     if(word.length()==0)
     {
         subsets.add("");
         return subsets;
     }
     else
     {
         String removed=word.substring(0,1);
         word=word.substring(1);
         subsets.add(removed);

         for(int i=0;i<word.length();i++)
         {
             for(int j=0; j<=i; j++){
               String temp=removed+word.substring(j,i+1);
               subsets.add(temp);
             }
         }
     }

     getSubsets();
     return subsets;
  }
}

子集生成器缺少一个可能的子集

1 个答案: