258. Add Digits

Given an integer num, repeatedly add all its digits until the result has only one digit, and return it.

 

Example 1:

Input: num = 38
Output: 2
Explanation: The process is
38 --> 3 + 8 --> 11
11 --> 1 + 1 --> 2 
Since 2 has only one digit, return it.

Example 2:

Input: num = 0
Output: 0 

class Solution {

public int addDigits(int num) {

if(num==0){

return 0;

}

if(num%9 == 0){

return 9;

}

return num%9;

}

}