phpOMS/Algorithm/Sort/BitonicSort.php

<?php
/**
 * Orange Management
 *
 * PHP Version 7.4
 *
 * @package   phpOMS\Algorithm\Sort;
 * @copyright Dennis Eichhorn
 * @license   OMS License 1.0
 * @version   1.0.0
 * @link      https://orange-management.org
 */
declare(strict_types=1);

namespace phpOMS\Algorithm\Sort;

/**
 * BitonicSort class.
 *
 * @package phpOMS\Algorithm\Sort;
 * @license OMS License 1.0
 * @link    https://orange-management.org
 * @since   1.0.0
 */
class BitonicSort implements SortInterface
{
    public static function sort(array $list, int $order = SortOrder::ASC) : array
    {
        $n = \count($list);

        if ($n < 2) {
            return $list;
        }

        $first  = self::sort(\array_slice($list, 0, $n / 2), SortOrder::ASC);
        $second = self::sort(\array_slice($list, $n / 2), SortOrder::DESC);

        return self::merge(\array_merge($first, $second), $order);
    }

    public static function merge(array $list, int $order) : array
    {
        $n = \count($list);

        if ($n === 1) {
            return $list;
        }

        $dist = $n / 2;
        for ($i = 0; $i < $dist; ++$i) {
            if ($list[$i]->compare($list[$i + $dist], $order)) {
                $old              = $list[$i];
                $list[$i]         = $list[$i + $dist];
                $list[$i + $dist] = $old;
            }
        }

        $first  = self::merge(\array_slice($list, 0, $n / 2), $order);
        $second = self::merge(\array_slice($list, $n / 2), $order);

        return \array_merge($first, $second);
    }
}