phpOMS/Algorithm/Knapsack/Continuous.php

<?php
/**
 * Karaka
 *
 * PHP Version 8.1
 *
 * @package   phpOMS\Algorithm\Knapsack
 * @copyright Dennis Eichhorn
 * @license   OMS License 1.0
 * @version   1.0.0
 * @link      https://karaka.app
 */

declare(strict_types=1);

namespace phpOMS\Algorithm\Knapsack;

/**
 * Continuous knapsack algorithm
 *
 * @package phpOMS\Algorithm\Knapsack
 * @license OMS License 1.0
 * @link    https://karaka.app
 * @since   1.0.0
 */
final class Continuous
{
    /**
     * Constructor
     *
     * @since 1.0.0
     * @codeCoverageIgnore
     */
    private function __construct()
    {
    }

    /**
     * Comparing items
     *
     * @param Item[] $a Item
     * @param Item[] $b Item
     *
     * @return int
     *
     * @since 1.0.0
     */
    private static function continuousComparator(array $a, array $b) : int
    {
        return $b['item']->getValue() / $b['item']->getCost() <=> $a['item']->getValue() / $a['item']->getCost();
    }

    /**
     * Fill the backpack with items
     *
     * @param array             $items    Items to fill the backpack with ['item' => Item, 'quantity' => ?]
     * @param BackpackInterface $backpack Backpack to fill
     *
     * @return BackpackInterface
     *
     * @since 1.0.0
     */
    public static function solve(array $items, BackpackInterface $backpack) : BackpackInterface
    {
        /* @phpstan-ignore-next-line */
        \usort($items, ['self', 'continuousComparator']);

        $availableSpace = $backpack->getMaxCost();

        foreach ($items as $item) {
            if ($availableSpace <= 0.0) {
                break;
            }

            $backpack->addItem(
                $item['item'],
                $quantity = \min($item['quantity'], $availableSpace / $item['item']->getCost())
            );

            $availableSpace -= $quantity * $item['item']->getCost();
        }

        return $backpack;
    }
}