Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

For example:

Given num = 38, the process is like: 3 + 8 = 11, 1 + 1 = 2. Since 2 has only one digit, return it.

public class Solution {public int getAllSum(int val) {int sum = 0;while (val > 0) {sum += val % 10;val /= 10;}return sum;}public  int addDigits(int num) {if (num <= 0) return 0;while (num >= 10) {num = getAllSum(num);}return num;}
}