isHappy.py

"""
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.
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.
Return true if n is a happy number, and false if not.

Example 1:
Input: n = 19
Output: true

Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

Runtime: 83 ms, faster than 5.15% of Python3 online submissions for Happy Number.
Memory Usage: 13.9 MB, less than 73.11% of Python3 online submissions for Happy Number.
"""


class Solution:
    def isHappy(self, n: int) -> bool:
        memo = set()
        while n != 1:
            n = sum([int(ch) ** 2 for ch in str(n)])
            if n in memo:
                return False
            else:
                memo.add(n)
        return True