202 Happy Number - Easy

Problem:

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

Problem Analysis:

• one should realise the importance of the hint of looping endlessly described in the question
• unhappy numbers follows a loop of repeated sequence of numbers which do not include 1

Solutions:

class Solution:
    def isHappy(self, n: int) -> bool:
        visit = set()
        
        while n not in visit:
            visit.add(n)
            n = self.sumOfSquares(n)
            
            if n == 1:
                return True
        return False
    
    def sumOfSquares(self,n):
        output=0
        
        while n:
            output += (n%10) **2
            n = n//10
        return output

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