202. Happy Number

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.Example: 19 is a happy number12 + 92 = 8282 + 22 = 6862 + 82 = 10012 + 02 + 02 = 1

解1：
用到了分解数字。
用到了集合，和集合的添加。
还有列表解析[i for i in nums]

class Solution(object):    def isHappy(self, n):        """        :type n: int        :rtype: bool        """        mem = set()        while n != 1:            nums = []            while n:                nums.append(n%10)                n = n/10            n = sum([i**2 for i in nums])            if n not in mem:                mem.add(n)            else:                return False        return True