Description
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?
Solution
Python3
class Solution:
def addDigits(self, num: int) -> int:
while num >= 10:
curr = 0
while num > 0:
curr += num % 10
num //= 10
num = curr
return num