Happy Number——Math

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 number

• 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
        """
        key = set()
        s = str(n)
        key.add(s)
        re = 0
        while True:
	        for i in range(len(s)):
	        	re += int(s[i])**2
	        if re == 1:
	        	return True 
	        s = str(re)
	        re = 0
	        if s in key:
	        	return False 
	        else:
	        	key.add(s)