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PHP Challenges: Check whether a given positive integer is a power of three

PHP Challenges - 1: Exercise-2 with Solution

Write a PHP program to check whether a given positive integer is a power of three.

Input : 9

Explanation :

PHP: Check whether a given positive integer is a power of three

Sample Solution :

PHP Code :

<?php
function is_Power_of_three($n)
{
      $x = $n;
      while ($x % 3 == 0) {
      $x /= 3;
     }
       
	if($x == 1)
    {
		return "$n is power of 3";
    }
    else
    {
		return "$n is not power of 3";
    }
  
}
print_r(is_Power_of_three(9)."\n");
print_r(is_Power_of_three(81)."\n");
print_r(is_Power_of_three(21)."\n");
?>

Sample Output: 

9 is power of 3                                             
81 is power of 3                                            
21 is not power of 3

Flowchart:

PHP Flowchart: Check whether a given positive integer is a power of three

PHP Code Editor:

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Previous: Write a PHP program to check whether a given positive integer is a power of two.
Next: Write a PHP program to check whether a given positive integer is a power of four.

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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