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:

Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        dict = set()
        sum = n
        while True:
            s = str(sum)
            sum = 0
            for i in s:
                sum += int(i)**2
            if sum in dict:
                return False
            dict.add(sum)
            if sum == 1:
                return True

你看这个数字它多快乐呀