"""
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
        """
        seen = []
        while n not in seen:
            if n == 1:
                return True
            seen.append(n)
            n = digit_sum(n)
        return False

def digit_sum(n):
    """
    :type n: int
    :rtype: int
    """
    result = 0
    while n != 0:
        digit = n % 10
        result += digit * digit
        n //= 10
    return result

