PHP 中的嵌套数据集结构

Question

我正在尝试实现 nested dataset structure in PHP (another description of the structure) 的面向对象版本。我已经创建了一个节点实现：

class Node
{
    private $parent;
    private $nodes = [];
    private $level = 1;
    private $left = 1;
    private $right = 2;

    /**
     * @return self|null
     */
    public function getParent()
    {
        return $this->parent;
    }

    private function setParent(self $parent = null)
    {
        $this->parent = $parent;
    }

    public function getLevel(): int
    {
        return $this->level;
    }

    private function setLevel(int $level)
    {
        $this->level = $level;
    }

    public function getLeft(): int
    {
        return $this->left;
    }

    private function setLeft(int $left)
    {
        $this->left = $left;
    }

    public function getRight(): int
    {
        return $this->right;
    }

    private function setRight(int $right)
    {
        $this->right = $right;
    }

    /**
     * @return static[]
     */
    public function getNodes(): array
    {
        return $this->nodes;
    }

    public function addNode(Node $new)
    {
        $new->setLevel($this->getLevel() + 1);
        $this->nodes[] = $new;

        // @todo
    }
}

但是我需要帮助来实现addNode方法，它应该向当前节点添加一个新节点并更新整个树，尤其是新添加的节点，父节点、子节点等

为了让一切变得更简单，我创建了简单的测试用例，它将检查是否一切都已正确实施：

$country = new Node();
$state = new Node();
$city = new Node();
$country->addNode($state);
$state->addNode($city);

assert($country->getLeft() === 1);
assert($country->getRight() === 6);
assert($country->getLevel() === 1);

assert($state->getLeft() === 2);
assert($state->getRight() === 5);
assert($state->getLevel() === 2);

assert($city->getLeft() === 3);
assert($city->getRight() === 4);
assert($city->getLevel() === 3);

Answer 1

您不应该定义 parent 或对它的引用，因为您可能最终会陷入引用循环，这在代码中不是坏事，但在设计中可能最终让您出错时无法理解代码。

至于 addNode 功能，你似乎是在正确的轨道上，

public function addNode(Node $new)
{
    //no need for getters and setters from inside the class
    $new->level = $this->level + 1;
    $this->nodes[] = $new;
    return $this;
}

虽然我不确定您要用 left 和 right 做什么。但我认为它是顶部 parent 一直向左，底部 child 一直向右。在那种情况下，我只是将它与级别区分开来。

我也不会使用 private 而是使用 protected，我主要是在这里这样做，这样我就可以一直往上走，而不需要 getter 和 setter 来使代码更紧凑，但是按照你的感觉去做喜欢：

class Node
{

    /**
     * @var static
     */
    protected $parent;
    /**
     * @var static[] 
     */
    protected $nodes = [];
    /**
     * @var int 
     */
    protected $level = 1;
    /**
     * @var int 
     */
    protected $left = 0;
    /**
     * @var int 
     */
    protected $right = 0;


    public function addNode(Node $new)
    {
        $new->level = $this->level + 1;
        $new->parent = $this;
        $new->left = $new->level - 1;
        if (empty($this->nodes)) {
            $this->right = 1;
        }
        $curr = $this;
        while (null !== $curr->parent) {
            //walking up to the current parent and telling it there is a new level added
            $curr->parent->right++;
            //setting the current level 1 up
            $curr = $curr->parent;
        }

        $this->nodes[] = $new;
        return $this;
    }
}

而且因为我 return $this，我可以链接所有内容，或者像

一样嵌套 addNode 调用

$country = new Node();
$state = new Node();
$city = new Node();
$country->addNode($state->addNode($city));

Answer 2

经过一天的休息和一杯咖啡，终于完成了这项工作。这并不像看起来那么容易，因为添加新节点时必须重写整棵树：

public function addChild(Node $new): void
{
    $this->nodes[] = $new;
    $new->setParent($this);
    $new->setLevel($this->getLevel() + 1);
    $new->setLeft($this->getLeft() + 1);
    $new->setRight($this->getLeft() + 2);

    $rootNode = $this;
    while (!empty($rootNode->getParent())) {
        $rootNode = $this->getParent();
    }

    $rootNode->setLeft(1);
    $this->updateTree($rootNode);
}

private function updateTree(Node $node): void
{
    $startIndex = $node->getLeft();
    foreach ($node->getChildren() as $child) {
        $child->setLeft(++$startIndex);
        $child->setRight(++$startIndex);

        if (count($child->getChildren())) {
            $this->updateTree($child);
            $startIndex = $this->getLastChild($child)->getRight();
        }
    }

    $node->setRight($this->getLastChild($node)->getRight() + 1);
}

private function getLastChild(Node $node): Node
{
    return $node->getChildren()[count($node->getChildren()) - 1];
}

class 即将在 GitHub 上发布。

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