[LeetCode] 202. Happy Number

 Problem : https://leetcode.com/problems/happy-number/

class Solution:
    def isHappy(self, n: int) -> bool:
        # use hashset to avoid looping in a cycle
        seen = set()
        
        while n not in seen:
            seen.add(n)
            
            nextNum = 0
            
            while n:
                t = n % 10
                nextNum += t * t
                n = n // 10
            
            n = nextNum
            
            if n == 1:
                return True
        
        return False