PHP Exercises: Test whether two lines PQ and RS are parallel

Last update on May 30 2022 11:44:30 (UTC/GMT +8 hours)

PHP: Exercise-56 with Solution

Write a PHP program to test whether two lines PQ and RS are parallel.
The four points are P(x1, y1), Q(x2, y2), R(x3, y3), S(x4, y4).

Input: −100 ≤ x1, y1, x2, y2, x3, y3, x4, y4 ≤ 100
Each value is a real number with at most 5 digits after the decimal point.

Sample Solution: -

PHP Code:

<?php
 fscanf(STDIN, '%d', $n); 
for ($i = 0; $i < $n; $i++) {
    fscanf(STDIN, '%f %f %f %f %f %f %f %f', $x1, $y1, $x2, $y2, $x3, $y3, $x4, $y4);
    $pq = INF;
    if ($x2 - $x1 !== 0.0) {
        $pq = ($y2 - $y1) / ($x2 - $x1);
    }
    $rs = INF;
    if ($x4 - $x3 !== 0.0) {
        $rs = ($y4 - $y3) / ($x4 - $x3);
    } 
    echo $pq === $rs ? 'PQ and RS are parallel.' : 'PQ and RS are not parallel.';
    echo PHP_EOL;
}
?>

Sample Input:
2
1.0 0.0 3.0 2.0 2.0 2.0 0.0 0.0
4.0 3.0 10.0 7.0 14.0 5.0 8.0 10.0

Sample Output:

PQ and RS are parallel.
PQ and RS are not parallel.

Flowchart:

PHP Code Editor:

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Previous: Write a PHP program that accepts six numbers as input and sorts them in descending order.
Next: Write a PHP program to compute the sum of the digits of a number.

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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