Algorithm-LeetCode/Solutions/0202.Happy_Number.py at main · ling67/Algorithm-LeetCode · GitHub

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"""
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
"""

class Solution:
    def isHappy(self, n: int) -> bool:
        s = {n}
        while n != 1:
            temp = 0
            while n:
                temp += (n % 10) ** 2
                n //= 10
            if temp in s:
                return False
            s.add(temp)
            n = temp
        return True