PHP Exercises: Reads an integer n and find the number of combinations

Last update on May 30 2022 11:48:42 (UTC/GMT +8 hours)

PHP: Exercise-51 with Solution

Write a PHP program which reads an integer n and find the number of combinations of a,b,c and d (0 ≤ a,b,c,d ≤ 9) where (a + b + c + d) will be equal to n.

Input:
n (1 ≤ n ≤ 50) .

Sample Solution: -

PHP Code:

<?php
 while (($input = trim(fgets(STDIN))) !== '') {
    $input = intval($input);
    $count = 0;
    for ($i=0; $i < 10; $i++) { 
        for ($j=0; $j < 10; $j++) { 
            for ($k=0; $k < 10; $k++) { 
                for ($l=0; $l < 10; $l++) { 
                    if ($i + $j + $k +$l === $input) {
                        $count++;
                    }
                }
            }
        }
    }
    echo "\nNumber of combinations of a,b,c and d: ";
    echo $count."\n";
}
?>

Sample Output:

Number of combinations of a,b,c and d: 56

Flowchart:

PHP Code Editor:

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Previous: Write a PHP program to compute the amount of the debt in n months.
Next: Write a PHP program to print the number of prime numbers which are less than or equal to a given integer.

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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