PHP 二叉树非递归遍历

 1 <?php

 2     #二叉树的非递归遍历

 3     class Node {

 4         public $data;

 5         public $left;

 6         public $right;

 7     }

 8 

 9     #前序遍历，和深度遍历一样

10     function preorder($root) {

11         $stack = array();

12         array_push($stack, $root);

13         while (!empty($stack)) {

14             $cnode = array_pop($stack);

15             echo $cnode->data . " ";

16             if ($cnode->right != null) array_push($stack, $cnode->right);

17             if ($cnode->left != null) array_push($stack, $cnode->left);

18         }

19     }

20 

21     #中序遍历

22     function inorder($root) {

23         $stack = array();

24         $cnode = $root;

25         while (!empty($stack) || $cnode != null) {

26             while ($cnode != null) {

27                 array_push($stack, $cnode);

28                 $cnode = $cnode->left;

29             }

30 

31             $cnode = array_pop($stack);

32             echo $cnode->data . " ";

33 

34             $cnode = $cnode->right;

35         }

36     }

37 

38     #后序遍历

39     #使用双栈实现

40     function postorder($root) {

41         $pushstack = array();

42         $visitstack = array();

43         array_push($pushstack, $root);

44 

45         while (!empty($pushstack)) {

46             $cnode = array_pop($pushstack);

47             array_push($visitstack, $cnode);

48             if ($cnode->left != null) array_push($pushstack, $cnode->left);

49             if ($cnode->right != null) array_push($pushstack, $cnode->right);

50         }

51 

52         while (!empty($visitstack)) {

53             $cnode = array_pop($visitstack);

54             echo $cnode->data . " ";

55         }

56     }

57 

58     $root = new Node();

59     $n1 = new Node();

60     $n11 = new Node();

61     $n12 = new Node();

62     $n2 = new Node();

63     $n21 = new Node();

64     $n22 = new Node();

65     $root->data = 0;

66     $n1->data = 1;

67     $n11->data = 11;

68     $n12->data = 12;

69     $n2->data = 2;

70     $n21->data = 21;

71     $n22->data = 22;

72     $root->left = $n1;

73     $root->right = $n2;

74     $n1->left = $n11;

75     $n1->right = $n12;

76     $n2->left = $n21;

77     $n2->right = $n22;

78 

79     preorder($root);

80     echo "<br>";

81     inorder($root);

82     echo "<br>";

83     postorder($root);

84 ?>