PHP 实现二叉树

 1 php
 2 
 3 /*----------------
 4 + 二叉树
 5 ----------------*/
 6 
 7 class BTree
 8 {
 9     // 数据域
10     protected $data;
11     // 左子树
12     protected $leftNode;
13     // 右子树
14     protected $rightNode;
15 
16     public function __construct($data = 0)
17     {
18         $this->data = $data;
19     }
20 
21     /**
22      * @param object $leftNode
23      */
24     public function setLeftNode(BTree $leftNode = null)
25     {
26         $this->leftNode = $leftNode;
27     }
28 
29     /**
30      * @param object $rightNode
31      */
32     public function setRightNode(BTree $rightNode = null)
33     {
34         $this->rightNode = $rightNode;
35     }
36 
37     public function getLeftNode()
38     {
39         // 判断自己瞎写的，当访问子节点不存在的时候，就重新实例化当前节点，data默认赋值为0，表示空节点。反正能够表示子节点不存在哈哈
40         if (!isset($this->leftNode)) {
41             return new self;
42         }
43         return $this->leftNode;
44     }
45 
46     public function getRightNode()
47     {
48         if (!isset($this->leftNode)) {
49             return new self;
50         }
51         return $this->rightNode;
52     }
53 
54     public function getData()
55     {
56         return $this->data;
57     }
58 }
59 
60 $rootNode = new BTree(1);
61 $zuo1Node = new BTree(2);
62 $you1Node = new BTree(3);
63 $zuo21Node = new BTree(4);
64 $you21Node = new BTree(5);
65 $zuo22Node = new BTree(6);
66 $rootNode->setLeftNode($zuo1Node);
67 $rootNode->setRightNode($you1Node);
68 $zuo1Node->setLeftNode($zuo21Node);
69 $zuo1Node->setRightNode($you21Node);
70 $you1Node->setLeftNode($zuo22Node);
71 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.
‘;
72 print_r($rootNode->getLeftNode()->getLeftNode()->getRightNode()->getData());
73 echo "
访问存在的节点，可以正常获取数据
";
74 print_r($rootNode->getLeftNode()->getRightNode()->getData());