Happy Number

Problem Statement

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.

Approach

• First of all we need to check if the number is already 1. If it is so, return True.

• Now if it is not so we dedicate a list of numbers to keep the track of the numbers that we already visited. If we visit them again, naturally we are in a loop and we cannot visit 1. Hence return False.

• Else its obvious we will visit 1 and one we hit 1 return True.

Algorithm

Code

class Solution:
    def isHappy(self, n: int) -> bool: 
        #Check if the number is already 1 
        if n == 1: return True

        numArray: list[int] = []

        #Now loop through until the number becomes 1 or it is in numArray
        while n not in numArray:
            numArray.append(n)
            tempNum: int = 0

            while n > 0:
                tempNum += ((n%10) * (n%10))
                n //= 10

            if tempNum == 1: return True

            n = tempNum

        #If this statement hits, then it's a false
        return False

Leetcode Result

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