PHP Challenges: Check whether a given number is an ugly number

PHP Challenges - 1: Exercise-19 with Solution

Write a PHP program to check whether a given number is an ugly number.

Input : 12

Ugly numbers are positive numbers whose only prime factors are 2, 3 or 5. The sequence 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, ...
shows the first 10 ugly numbers.
Note: 1 is typically treated as an ugly number.

Explanation :

Sample Solution :

PHP Code :

<?php
// Function to check if a number is ugly
function is_ugly($num)
{
    // Store the original number in a variable
    $z = $num;
    
    // Check if the number is 0
    if ($num == 0)
    {
        // If so, return a message indicating it's not an Ugly number
        return "$num is not an Ugly number";
    }
    
    // Define an array of prime factors that make a number ugly
    $x = array(2, 3, 5);
    
    // Iterate through each prime factor
    foreach ($x as $i)
    {
        // While the number is divisible by the current prime factor
        while ($num % $i == 0)
        {
            // Divide the number by the prime factor
            $num /= $i;
        }
    }
    
    // If the number becomes 1 after dividing by all prime factors
    if ($num == 1)
    {
        // Return a message indicating it's an Ugly number
        return "$z is an Ugly number";
    }
    else
    {
        // Otherwise, return a message indicating it's not an Ugly number
        return "$z is not an Ugly number";
    }
}

// Test the is_ugly function with different inputs and print the results
print(is_ugly(12) . "\n");
print(is_ugly(7) . "\n");
?>

Explanation:

Here is a brief explanation of the above PHP code:

• Function definition:
• The code defines a function named "is_ugly()" which checks if a given number is an ugly number. An ugly number is a positive integer whose prime factors are only 2, 3, and 5.
• Inside the function:
• It stores the original number in a variable '$z'.
• It checks if the number is 0. If so, it returns a message indicating that it's not an ugly number.
• It defines an array '$x' containing the prime factors that make a number ugly (2, 3, and 5).
• It iterates through each prime factor in the array.
• Within each iteration, it divides the number by the current prime factor until it's no longer divisible.
• After the loop, if the number becomes 1, it returns a message indicating that it's an ugly number. Otherwise, it returns a message indicating that it's not an ugly number.
• Function Call & Testing:
• The "is_ugly()" function is called twice with different input numbers (12 and 7).
• Finally the "print()" function displays whether each input number is an ugly number or not.

Sample Output:

12 is an Ugly number                                        
7 is not an Ugly number 

Flowchart:

PHP Code Editor:

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