Sample input:
999999999999999999999
9
9999999999999999999999999999998
0

Sample output
999999999999999999999 is a multiple of 9 and has 9-degree 3.
9 is a multiple of 9 and has 9-degree 1.
9999999999999999999999999999998 is not a multiple of 9.


解法: 每次把所有位數加總 如果是9的倍數就往下遞迴



import java.util.Scanner;

public class UVA10922 {

 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  while (sc.hasNext()) {

   String str = sc.nextLine();

   if (str.equals("0"))
    break;

   System.out.print(str + " is ");

   int num = 0, t_num = 0, count = 0;

   for (int i = 0; i < str.length(); i++)
    num += Integer.parseInt(str.substring(i, i + 1));

   if (num % 9 == 0)
    count++;

   while (num % 9 == 0 && num > 9) {

    t_num = num;

    count++;

    num = 0;

    while (t_num > 0) {

     num += t_num % 10;
     t_num /= 10;

    }

   }

   System.out.println(num == 9 ? "a multiple of 9 and has 9-degree "
     + count + "." : "not a multiple of 9.");

  }

  sc.close();
 }

}