如何对以第一个字符开头的字符串数组进行排序？

Posted 2023-02-04

我想生成字符串的“子集”，并按特定顺序打印输出。例如，“ rum”，我希望输出为[rum，ru，rm，r，um，u，m]我的代码在下面，现在我的输出是[rum，ru，rm，um，r，u，m]。如何更改代码以使其正常工作？

import java.util.*;
public class SubstringGenerator 
    String word;

    public SubstringGenerator(String x)  word = x;

    public static void main(String[] args)
        SubstringGenerator a = new SubstringGenerator("rum");
        List b = a.subsets();
        Collections.sort(b, Collections.reverseOrder(Comparator.comparing(String::length)));
        System.out.println(b);
    

    public List subsets()
        ArrayList<String> subsets = new ArrayList<String>();
        int len = word.length();
        for (int i = 0; i < Math.pow(2,len); i++)
            String a = "";
            for (int j = 0; j < len; j++)
                if ((i & (int) (Math.pow(2,j))) > 0) a += word.charAt(j) + "";
            
            subsets.add(a);
        
        return subsets;
    

答案

import java.util.*; import java.lang.Math; public class SubstringGenerator String word; public SubstringGenerator(String x) word = x; public static void main(String[] args) SubstringGenerator a = new SubstringGenerator("rum"); List b = a.subsets(); System.out.println(b); public List subsets() ArrayList<String> subsets = new ArrayList<String>(); int len = word.length(); for (int i = (int)(Math.pow(2,len)-1.0); i >0; i--) String a = ""; String b= Integer.toBinaryString(i); while(b.length()!=word.length()) b="0"+b; for(int j=0; j<b.length(); j++) if (b.charAt(j)=='1') a+=word.substring(j, j+1); subsets.add(a); return subsets;