PHP Exercises: Create maximum number of regions obtained by drawing n given straight lines

Last update on May 30 2022 11:45:52 (UTC/GMT +8 hours)

PHP: Exercise-67 with Solution

If you draw a straight line on a plane, the plane is divided into two regions. For example, if you pull two straight lines in parallel, you get three areas, and if you draw vertically one to the other you get 4 areas.
Write a PHP program to create maximum number of regions obtained by drawing n given straight lines.

Input: (1 ≤ n ≤ 10,000)

Sample Solution: -

PHP Code:

<?php
while (($line = trim(fgets(STDIN))) !== '') {
    $n = (int)$line;
    $result = 2;
    for ($i = 2; $i <= $n; $i++) {
        $result += $i;
    } 
    echo 'Maximum number of regions: ';
    echo $result, PHP_EOL;
}
?>

Sample Input:
5

Sample Output:

Maximum number of regions: 16

Flowchart:

PHP Code Editor:

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Previous: Print the number of combinations.
Next: Write a PHP program to test whether AB and CD are orthogonal or not.

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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