Add Digits.py

# https://leetcode.com/problems/add-digits/

# 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.
#
# Follow up:
# Could you do it without any loop/recursion in O(1) runtime?



# 38 = 3 * 10 + 8

class Solution(object):
    def addDigits(self, num):
        """
        :type num: int
        :rtype: int
        """
        if num == 0:
            return 0
        elif num % 9 == 0:
            return 9
        return num % 9