php实现的二叉树遍历算法示例_PHP教程

php实现的二叉树遍历算法示例

2021-05-28 16:52aarontong00 PHP教程

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实现的二叉树遍历算法示例

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