本文实例讲述二叉树遍历算法 php实现。分享给大家供大家参考，具体如下：
创建的二叉树如下图所示
php代码如下所示：
<?php
class 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 f
echo '<br/>';
//中序遍历
ergodic::midorder($a); //结果是： h d i b g a e c f
echo '<br/>';
//后序遍历
ergodic::endorder($a); //结果是: h i d g b e f c a
以上就是二叉树遍历算法-php的示例的详细内容。