PHP 实现二叉树

代码

<?php

/*----------------
+ 二叉树
----------------*/

class BTree
{
    // 数据域
    protected $data;
    // 左子树
    protected $leftNode;
    // 右子树
    protected $rightNode;

    public function __construct($data = 0)
    {
        $this->data = $data;
    }

    /**
     * @param object $leftNode
     */
    public function setLeftNode(BTree $leftNode = null)
    {
        $this->leftNode = $leftNode;
    }

    /**
     * @param object $rightNode
     */
    public function setRightNode(BTree $rightNode = null)
    {
        $this->rightNode = $rightNode;
    }

    public function getLeftNode()
    {
        // 判断自己瞎写的，当访问子节点不存在的时候，就重新实例化当前节点，data默认赋值为0，表示空节点。反正能够表示子节点不存在哈哈
        if (!isset($this->leftNode)) {
            return new self;
        }
        return $this->leftNode;
    }

    public function getRightNode()
    {
        if (!isset($this->leftNode)) {
            return new self;
        }
        return $this->rightNode;
    }

    public function getData()
    {
        return $this->data;
    }
}

$rootNode = new BTree(1);
$zuo1Node = new BTree(2);
$you1Node = new BTree(3);
$zuo21Node = new BTree(4);
$you21Node = new BTree(5);
$zuo22Node = new BTree(6);
$rootNode->setLeftNode($zuo1Node);
$rootNode->setRightNode($you1Node);
$zuo1Node->setLeftNode($zuo21Node);
$zuo1Node->setRightNode($you21Node);
$you1Node->setLeftNode($zuo22Node);
echo '访问的节点不存在时，返回空，0表示空节点，或者设置为null也行.<br>';
print_r($rootNode->getLeftNode()->getLeftNode()->getRightNode()->getData());
echo "<br>访问存在的节点，可以正常获取数据<br>";
print_r($rootNode->getLeftNode()->getRightNode()->getData());