Happy Number - Leetcode

happy_number.py

#https://leetcode.com/explore/featured/card/30-day-leetcoding-challenge/528/week-1/3284/
class Solution(object):
    def isHappy(self, n):
        """
        :type n: int
        :rtype: bool
        """
        
        exists = set()
        while n != 1:
            n = sum( [int(i)**2 for i in str(n)] )
            if n in exists:
                return False
            else:
                exists.add(n)
        return True