Leetcode 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

Constraints:

• 0 <= num <= 231 - 1

class Solution(object):
    def addDigits(self, num):
        """
        :type num: int
        :rtype: int
        """
        list = []
        s = str(num)
        
        while len(s) > 1:
            for i in s:
                list.append(int(i))
            s = sum(list)
            s = str(s)
            list = []
        
        return s