算法提高 数字黑洞

 1 import java.util.ArrayList;
 2 import java.util.Arrays;
 3 import java.util.Collections;
 4 import java.util.List;
 5 import java.util.Scanner;
 6 
 7 class Main{
 8     static int sum;
 9     public static void main(String[] args) {
10         Scanner input = new Scanner(System.in);
11         String temp = input.next();
12         StringBuffer s = new StringBuffer(temp);
13         while(!s.toString().equals("6174")){
14             char[] a = s.toString().toCharArray();
15             Arrays.sort(a);
16             s = new StringBuffer(String.valueOf(a));
17             int h = Integer.parseInt(s.reverse().toString())-Integer.parseInt(s.reverse().toString());
18             s = new StringBuffer(h+"");
19             while(s.length()!=4){
20                 s.append("0");
21             }
22             sum++;
23         }
24         System.out.println(sum);
25         
26     }
27 }