202. Happy Number-快乐数

Write an algorithm to determine if a number n 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.
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
Example 2:

Input: n = 2
Output: false

Constraints:

• 1 <= n <= 231 - 1

Solution in python:

class Solution:
    def isHappy(self, n: int) -> bool:
        aset = set()
        while True:
            result = 0
            while n > 0:
                n, r = divmod(n, 10)
                result += r**2
            if result == 1: 
                return True
            if result in aset: 
                return False
            else: 
                n = result
                aset.add(result)