本文实例讲述了php实现的二叉树遍历算法。分享给大家供大家参考，具体如下：
今天使用php来实现二叉树的遍历
创建的二叉树如下图所示
php代码如下所示：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
<?phpclass Node { public $value; public $child_left; public $child_right;}final class Ergodic { //前序遍历:先访问根节点，再遍历左子树，最后遍历右子树；并且在遍历左右子树时，仍需先遍历根节点，然后访问左子树，最后遍历右子树 public static function preOrder($root){ $stack = array(); array_push($stack, $root); while(!empty($stack)){ $center_node = array_pop($stack); echo $center_node->value . ' '; //先把右子树节点入栈，以确保左子树节点先出栈 if($center_node->child_right != null) array_push($stack, $center_node->child_right); if($center_node->child_left != null) array_push($stack, $center_node->child_left); } } //中序遍历:先遍历左子树、然后访问根节点，最后遍历右子树；并且在遍历左右子树的时候。仍然是先遍历左子树，然后访问根节点，最后遍历右子树 public static function midOrder($root){ $stack = array(); $center_node = $root; while (!empty($stack) || $center_node != null) { while ($center_node != null) { array_push($stack, $center_node); $center_node = $center_node->child_left; } $center_node = array_pop($stack); echo $center_node->value . ' '; $center_node = $center_node->child_right; } } //后序遍历:先遍历左子树，然后遍历右子树，最后访问根节点；同样，在遍历左右子树的时候同样要先遍历左子树，然后遍历右子树，最后访问根节点 public static function endOrder($root){ $push_stack = array(); $visit_stack = array(); array_push($push_stack, $root); while (!empty($push_stack)) { $center_node = array_pop($push_stack); array_push($visit_stack, $center_node); //左子树节点先入$pushstack的栈，确保在$visitstack中先出栈 if ($center_node->child_left != null) array_push($push_stack, $center_node->child_left); if ($center_node->child_right != null) array_push($push_stack, $center_node->child_right); } while (!empty($visit_stack)) { $center_node = array_pop($visit_stack); echo $center_node->value . ' '; } }}//创建二叉树$a = new Node();$b = new Node();$c = new Node();$d = new Node();$e = new Node();$f = new Node();$g = new Node();$h = new Node();$i = new Node();$a->value = 'A';$b->value = 'B';$c->value = 'C';$d->value = 'D';$e->value = 'E';$f->value = 'F';$g->value = 'G';$h->value = 'H';$i->value = 'I';$a->child_left = $b;$a->child_right = $c;$b->child_left = $d;$b->child_right = $g;$c->child_left = $e;$c->child_right = $f;$d->child_left = $h;$d->child_right = $i;//前序遍历Ergodic::preOrder($a); //结果是：A B D H I G C E Fecho '<br/>';//中序遍历Ergodic::midOrder($a); //结果是： H D I B G A E C Fecho '<br/>';//后序遍历Ergodic::endOrder($a); //结果是: H I D G B E F C A |
希望本文所述对大家PHP程序设计有所帮助。
