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

Last update on December 20 2024 10:22:21 (UTC/GMT +8 hours)

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 :

PHP: Check whether a given number is an ugly number

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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