【leetcode 简单】 第七十二题 各位相加

class Solution:
    def addDigits(self, num):
        """
        :type num: int
        :rtype: int
        """
        if num < 10: return num
        sum = num
        while sum >=10:
            sum = 0
            while num > 0:
                sum += num %10
                num = int(num/10)
            num = sum #第二次进入num>0循环的条件

        return sum