Happy Number

Problem Statement

Given a positive integer n, determine if it is a happy number.

A happy number is defined by the following process:

Starting with any positive integer, replace the number by the sum of the squares of its digits.
Repeat this process until the number equals 1 (where it will stay), or it loops endlessly in a cycle that does not include 1.
Numbers for which this process ends in 1 are considered happy.

Return true if n is a happy number, otherwise return false.

Examples

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

class Solution:
    def isHappy(self, n: int) -> bool:
        # Your code here
        pass

Solution 1 - Using a set to detect cycles in the process. Time complexity: O(log² n), Space complexity: O(k) where k is the number of unique numbers seen before a cycle is detected.