samhavens/merge_sort_php

## merge_sort_php
<html>
<head>
	<title>Merge Sort with Inversion Count Using PHP</title>
</head>
<body>
	<form action="openfile.php" method="post">
	Name of input file: <input type="text" name="name"><br>
	<input type="submit">
	</form>

	<?php
	if (!empty($_POST["name"])) {
		$a = [];
		#put test data into array $a
		$file = fopen($_POST["name"], "r");
			while(!feof($file)) {
				$a[] =  (int) fgets($file);
			}
		fclose($file);

		echo "Input array: <br>";
		foreach ($a as $key => $value) {
			echo "{$value} <br>";
		}
		echo "<br>";

		function merge_sort($array) {
			$left = [];
			$right = [];
			global $inversion_count;
			$inversion_count = 0;

			#This is the base case
			if (count($array) == 1) {
				return $array;
				echo "this many times";
			}
			#This is the n > 1 case
			else {
				$middle = (int) round(count($array)/2);
				#echo "<br> {$middle} <br>";
				$left = array_slice($array, 0, $middle);
				$right = array_slice($array, $middle);
				$array = [];
				$left = merge_sort($left);
				$right = merge_sort($right);

				while (!empty($left) && !empty($right)) {
					if ($left[0] < $right[0]) {
						$array[] = array_shift($left);
					}
					else {
						$inversion_count += count($left);
						$array[] = array_shift($right);
					}
				}
			}
			return array_merge($array, $left, $right);
		}
		echo "Sorted array: <br>";
		foreach (merge_sort($a) as $key => $value) {
			echo "{$value} <br>";
		}
		echo '<br>' . "Number of inversions: " . $inversion_count;
	}
	?>
</body>
</html>
	<html>
	<head>
	<title>Merge Sort with Inversion Count Using PHP</title>
	</head>
	<body>
	<form action="openfile.php" method="post">
	Name of input file: <input type="text" name="name"><br>
	<input type="submit">
	</form>

	<?php
	if (!empty($_POST["name"])) {
	$a = [];
	#put test data into array $a
	$file = fopen($_POST["name"], "r");
	while(!feof($file)) {
	$a[] = (int) fgets($file);
	}
	fclose($file);

	echo "Input array: <br>";
	foreach ($a as $key => $value) {
	echo "{$value} <br>";
	}
	echo "<br>";

	function merge_sort($array) {
	$left = [];
	$right = [];
	global $inversion_count;
	$inversion_count = 0;

	#This is the base case
	if (count($array) == 1) {
	return $array;
	echo "this many times";
	}
	#This is the n > 1 case
	else {
	$middle = (int) round(count($array)/2);
	#echo "<br> {$middle} <br>";
	$left = array_slice($array, 0, $middle);
	$right = array_slice($array, $middle);
	$array = [];
	$left = merge_sort($left);
	$right = merge_sort($right);

	while (!empty($left) && !empty($right)) {
	if ($left[0] < $right[0]) {
	$array[] = array_shift($left);
	}
	else {
	$inversion_count += count($left);
	$array[] = array_shift($right);
	}
	}
	}
	return array_merge($array, $left, $right);
	}
	echo "Sorted array: <br>";
	foreach (merge_sort($a) as $key => $value) {
	echo "{$value} <br>";
	}
	echo '<br>' . "Number of inversions: " . $inversion_count;
	}
	?>
	</body>
	</html>