258. Add Digits

Easy

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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

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

class Solution:
    def addDigits(self, num: int) -> int:
        if num == 0:
            return 0
        number_of_digits = int(math.log10(num))+1
        while number_of_digits != 1:
            total = 0
            while num != 0:
                digit = num % 10
                num = int(num/10)
                total = total + digit
            num = total
            number_of_digits = int(math.log10(num))+1
        return num