php实现的二叉树遍历算法示例代码

企鹅博客 2019年8月12日09:40:01 评论 245

这篇文章主要介绍了php实现的二叉树遍历算法,结合具体实例形式分析了php针对二叉树的常用前序、中序及后序遍历算法实现技巧,需要的朋友可以参考下

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:

<?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

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