Day-26_Add_Digits.py

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

Example:

Input: 38
Output: 2 
Explanation: 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?

   Hide Hint #1  
A naive implementation of the above process is trivial. Could you come up with other methods?
   Hide Hint #2  
What are all the possible results?
   Hide Hint #3  
How do they occur, periodically or randomly?
   Hide Hint #4  
You may find this Wikipedia article useful.

'''

class Solution(object):
    def addDigits(self, num):
        while num>9:
            res = 0
            for i in str(num):
                res+=int(i)
                num = res
        return num