PHP 背包问题动态规划

<?php

class Item{

    private $weight = 0;
    private $price = 0;
    private $name = "";

    /**
     * Item constructor.
     * @param string $name
     * @param int $price
     * @param int $weight
     */
    public function __construct(string $name ,int $weight, int $price)
    {
        $this->name = $name;
        $this->weight = $weight;
        $this->price = $price;
    }


    /**
     * @return string
     */
    public function getName(): string
    {
        return $this->name;
    }

    /**
     * @param string $name
     */
    public function setName(string $name)
    {
        $this->name = $name;
    }


    /**
     * @return int
     */
    public function getWeight(): int
    {
        return $this->weight;
    }

    /**
     * @param int $weight
     */
    public function setWeight(int $weight)
    {
        $this->weight = $weight;
    }

    /**
     * @return int
     */
    public function getPrice(): int
    {
        return $this->price;
    }

    /**
     * @param int $price
     */
    public function setPrice(int $price)
    {
        $this->price = $price;
    }

}

class Bags{

    const DEFAULT_VALUE = 0;
    private $capacity = 0;
    private $items = [];
    private $tables = [];



    public function __construct( $capacity )
    {
        $this->capacity = $capacity;
    }

    public function addItem( Item $item ){
        return array_push($this->items, $item);
    }

    //获取背包最大价值
    public function getMaxValue(){

        //建立二维表
        $this->initTable();
        $capacitys = $this->getCapacity();
        $itemCount = count($this->items);
        $curItem = null;
        $curVal = 0;
        $curWeight = 0;
        for ( $i = 1; $i <= $itemCount; $i++ ){
            for( $curCapacity=1; $curCapacity <= $capacitys; $curCapacity++ ){
                $curItem = $this->items[$i-1];
                $curVal = $curItem->getPrice();
                $curWeight = $curItem->getWeight();

                $this->tables[$i][$curCapacity] = $this->tables[$i-1][$curCapacity] ?? static::DEFAULT_VALUE;
                $spareVal = $this->tables[$i-1][$curCapacity-$curWeight]['val'] ?? static::DEFAULT_VALUE;

                $lastVal = $this->tables[$i-1][$curCapacity]['val'] ?? static::DEFAULT_VALUE;
                $maxVal = $curVal + $spareVal;
                if( $curCapacity >= $curWeight
                    &&  ($maxVal > $lastVal) ){
                    $content = "name:".$curItem->getName()." ,price: ".$curItem->getPrice() ." weight:".$curItem->getWeight();
                    $this->tables[$i][$curCapacity] = [
                        'val'=>$maxVal ,
                        'content'=> array_merge( $this->tables[$i-1][$capacitys-$curWeight]['content']??[], [$content])
                    ];
                }
            }
        }
        return $this->tables[$itemCount][$capacitys];
    }

    public function initTable(){

        $capacitys = $this->getCapacity();
        $itemCount = count($this->items);
        for ( $i = 1; $i <= $itemCount; $i++ ){
            for( $j=1; $j<= $capacitys; $j++ ){
                $this->tables[$i][$j] = [
                    'val'=> static::DEFAULT_VALUE,
                    'content'=>''
                ];
            }
        }
        return $this->tables;
    }

    //根据背包计算
    public function getCapacity(){
        return $this->capacity;
    }

    public function getTables(){
        return $this->tables;
    }
}


$bag = new Bags( 4 );


$item1 = new Item('吉他', 1, 1500);
$item2 = new Item('音响', 4, 3000);
$item3 = new Item('笔记本电脑', 3, 2000);
$item4 = new Item('钻石',1 , 6000);
$item5 = new Item('钻石2',1 , 20000);



$bag->addItem($item5);
$bag->addItem($item4);
$bag->addItem($item1);
$bag->addItem($item2);
$bag->addItem($item3);


$maxVal = $bag->getMaxValue();
print_r($maxVal);