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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 :

PHP: Check whether a given number is an ugly number

Sample Solution :

PHP Code :

<?php
function is_ugly($num)
  {
     $z = $num;
     if ($num == 0)
       {
            return "$num is not an Ugly number";
       }
       
       $x = array(2, 3, 5);
      foreach ($x as $i)
      {
            while ($num % $i == 0)
            {
                $num /= $i;
                 }
         }         
       if ($num==1)
         {
              return "$z is an Ugly number";
         }
         else
         {
              return "$z is not an Ugly number";
         }

 }    

print(is_ugly(12)."\n");
print(is_ugly(7)."\n");
?>

Sample Output: 

12 is an Ugly number                                        
7 is not an Ugly number

Flowchart:

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

PHP Code Editor:

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Previous: Write a PHP program where you take any positive integer n, if n is even, divide it by 2 to get n / 2. If n is odd, multiply it by 3 and add 1 to obtain 3n + 1. Repeat the process until you reach 1.
Next: Write a PHP program to get the Hamming numbers upto a given numbers also check whether a given number is a Hamming number.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC