258. Add Digits

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?

思路：两次循环

代码：python3

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