leetcode add digits

视频分析：
http://v.youku.com/v_show/id_XMTMzMjUwNjk3Mg==.html
题干：
Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.

For example:

Given num = 38, 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?

代码：

from math import *class Solution(object):    def sumdig(self,num):        re=0        tmp=num        while True:            re+=tmp%10            tmp=tmp//10            if tmp<=0:                break        return re    def addDigits2(self, num):        """        :type num: int        :rtype: int        """        tmp=num        while True:            if tmp<10 and tmp>=0:                return tmp            else:                tmp=self.sumdig(tmp)    def addDigits(self, num):        return int(num-9*floor((num-1)/9))