202. Happy Number

Question 202

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

Write an algorithm to determine if a number 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, and 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 numbers.

Example:

Input: 19
Output: true
Explanation: 
1**2 + 9**2 = 82
8**2 + 2**2 = 68
6**2 + 8**2 = 100
1**2 + 0**2 + 0**2 = 1

Answer

注意：最終判斷條件不可以是單純的 “ < 10” ，因為個位數 7 也會是一個 Happy Num

class Solution:
    def isHappy(self, n):
        res = 0
        HappyNum = [1,7]
        print(n)
        while ( n > 0 ):
            res += (n%10)**2
            n = n // 10
        
        if(res < 10):
            if res in HappyNum:
                return True
            else:
                return False
        
        return self.isHappy(res)