PHP Exercises: Test whether AB and CD are orthogonal or not

Last update on May 30 2022 11:40:35 (UTC/GMT +8 hours)

PHP: Exercise-68 with Solution

There are four different points on a plane, P(xp,yp), Q(xq, yq), R(xr, yr) and S(xs, ys). Write a PHP program to test whether AB and CD are orthogonal or not.
xp,yp, xq, yq, xr, yr, xs and ys are -100 to 100 respectively and each value can be up to 5 digits after the decimal point It is given as a real number including the number of.

Sample Solution: -

PHP Code:

<?php
define('EPS', 1e-8);
    $a = fscanf(STDIN, '%f %f %f %f %f %f %f %f');
    $line = array();
    $line[] = $a[1] - $a[3] === 0.0 ? INF : ($a[0] - $a[2]) / ($a[1] - $a[3]);
    $line[] = $a[5] - $a[7] === 0.0 ? INF : ($a[4] - $a[6]) / ($a[5] - $a[7]);
    if (max($line) === INF && min($line) === 0 || abs($line[0] * $line[1] + 1.0) < EPS) {
        echo 'Orthogonal';
    } else {
        echo 'Not orthogonal';
    }
    echo PHP_EOL;
?>

Sample Input:
3.5 4.5 2.5 -1.5 3.5 1.0 0.0 4.5

Sample Output:

Not orthogonal

Flowchart:

PHP Code Editor:

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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