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());