Add Digits

Problem: Add Digits

The answer will only be 1,2,3,4,5,6,7,8,9 except 0 for 0. And the answer iterate by nine.

Code in Python:

class Solution(object):
    def addDigits(self, num):
        """
        :type num: int
        :rtype: int
        """
        if num == 0: return 0
        ans = [9, 1, 2, 3, 4, 5, 6, 7, 8]
        return ans[num % 9]