数据结构之利用PHP实现二分搜索树(2)

<?php
require 'BinarySearchTree.php';
$binarySearchTree = new BinarySearchTree();
$binarySearchTree->add(45);
$binarySearchTree->add(30);
$binarySearchTree->add(55);
$binarySearchTree->add(25);
$binarySearchTree->add(35);
$binarySearchTree->add(50);
$binarySearchTree->add(65);
$binarySearchTree->add(15);
$binarySearchTree->add(27);
$binarySearchTree->add(31);
$binarySearchTree->add(48);
$binarySearchTree->add(60);
$binarySearchTree->add(68);
//下面是预期想要的结果
/**
 *                     45
 *           /                  
 *          30                   55
 *        /                    /   
 *      25       35         50       65
 *     /       /          /       /  
 *   15   27  31         48       60     68
 *
 */
$binarySearchTree->preTraversal();
/**
打印输出
45
-----30
----------25
---------------15
--------------------null
--------------------null
---------------27
--------------------null
--------------------null
----------35
---------------31
--------------------null
--------------------null
---------------null
-----55
----------50
---------------48
--------------------null
--------------------null
---------------null
----------65
---------------60
--------------------null
--------------------null
---------------68
--------------------null
--------------------null
 */

Tips：可以看到打印输出结果和预期一致。

2.7 二分搜索树中序遍历

遍历操作就是把所有节点都访问一次，后序遍历 是先递归遍历右儿子树，再访问节点，然后再递归遍历右儿子树，最后的顺序输出结果是有序的：

/** * 中序遍历 */ public function midTraversal() { $this->recursionMidTraversal($this->root, 0); } /** * 中序遍历的递归 */ public function recursionMidTraversal($root, $sign_num) { if ($root == null) { echo $this->getSign($sign_num);//打印深度 echo "null<br>"; return; } $this->recursionMidTraversal($root->left, $sign_num + 1); echo $this->getSign($sign_num);//打印深度 echo $root->e . "<br>"; $this->recursionMidTraversal($root->right, $sign_num + 1); }

下面是打印结果:

<?php
require 'BinarySearchTree.php';
$binarySearchTree = new BinarySearchTree();
$binarySearchTree->add(45);
$binarySearchTree->add(30);
$binarySearchTree->add(55);
$binarySearchTree->add(25);
$binarySearchTree->add(35);
$binarySearchTree->add(50);
$binarySearchTree->add(65);
$binarySearchTree->add(15);
$binarySearchTree->add(27);
$binarySearchTree->add(31);
$binarySearchTree->add(48);
$binarySearchTree->add(60);
$binarySearchTree->add(68);
//下面是预期想要的结果
/**
 *                     45
 *           /                  
 *          30                   55
 *        /                    /   
 *      25       35         50       65
 *     /       /          /       /  
 *   15   27  31         48       60     68
 *
 */
$binarySearchTree->midTraversal();
/**
打印输出
--------------------null
---------------15
--------------------null
----------25
--------------------null
---------------27
--------------------null
-----30
--------------------null
---------------31
--------------------null
----------35
---------------null
45
--------------------null
---------------48
--------------------null
----------50
---------------null
-----55
--------------------null
---------------60
--------------------null
----------65
--------------------null
---------------68
--------------------null
 */

Tips：可以看到打印输出结果和预期一致，但是此时的遍历顺序变了，最后的顺序输出结果是有序的。

2.8 二分搜索树后序遍历

遍历操作就是把所有节点都访问一次，后序遍历 是先递归遍历左儿子树，然后再递归遍历右儿子树，再访问节点：