本文實例講述了PHP實現的線索二元樹及二元樹遍歷方法。分享給大家參考，具體如下：
<?php require 'biTree.php'; $str = 'ko#be8#tr####acy#####'; $tree = new BiTree($str); $tree->createThreadTree(); echo $tree->threadList() . "\n";从第一个结点开始遍历线索二叉树 echo $tree->threadListReserv();从最后一个结点开始反向遍历 ?>
biTree.php：
<?
/**
* PHP实现二叉树
*
* @author zhaojiangwei
* @since 2011/10/25 10:32
*/
//结点类
class Node{
private $data = NULL;
private $left = NULL;
private $right = NULL;
private $lTag = 0;
private $rTag = 0;
public function Node($data = false){
$this->data = $data;
}
//我不喜欢使用魔术方法
public function getData(){
return $this->data;
}
public function setData($data){
$this->data = $data;
}
public function getLeft(){
return $this->left;
}
public function setLeft($left){
$this->left = $left;
}
public function getRight(){
return $this->right;
}
public function setRight($right){
$this->right = $right;
}
public function getLTag(){
return $this->lTag;
}
public function setLTag($tag){
$this->lTag = $tag;
}
public function getRTag(){
return $this->rTag;
}
public function setRTag($tag){
$this->rTag = $tag;
}
}
//线索二叉树类
class BiTree{
private $datas = NULL;//要导入的字符串;
private $root = NULL; //根结点
private $leafCount = 0;//叶子结点个数
private $headNode = NULL; //线索二叉树的头结点
private $preNode = NULL;//遍历线索化二叉树时保存前一个遍历的结点
public function BiTree($datas){
is_array($datas) || $datas = str_split($datas);
$this->datas = $datas;
$this->backupData = $this->datas;
$this->createTree(TRUE);
}
//前序遍历创建树
//$root 判断是不是要创建根结点
public function createTree($root = FALSE){
if(emptyempty($this->datas)) return NULL;
$first = array_shift($this->datas);
if($first == '#'){
return NULL;
}else{
$node = new Node($first);
$root && $this->root = $node;
$node->setLeft($this->createTree());
$node->setRight($this->createTree());
return $node;
}
}
//返回二叉树叶子结点的个数
public function getLeafCount(){
$this->figureLeafCount($this->root);
return $this->leafCount;
}
private function figureLeafCount($node){
if($node == NULL)
return false;
if($this->checkEmpty($node)){
$this->leafCount ++;
}else{
$this->figureLeafCount($node->getLeft());
$this->figureLeafCount($node->getRight());
}
}
//判断结点是不是叶子结点
private function checkEmpty($node){
if($node->getLeft() == NULL && $node->getRight() == NULL){
return true;
}
return false;
}
//返回二叉树深度
public function getDepth(){
return $this->traversDepth($this->root);
}
//遍历求二叉树深度
public function traversDepth($node){
if($node == NULL){
return 0;
}
$u = $this->traversDepth($node->getLeft()) + 1;
$v = $this->traversDepth($node->getRight()) + 1;
return $u > $v ? $u : $v;
}
//返回遍历结果,以字符串的形式
//$order 按遍历形式返回,前中后
public function getList($order = 'front'){
if($this->root == NULL) return NULL;
$nodeList = array();
switch ($order){
case "front":
$this->frontList($this->root, $nodeList);
break;
case "middle":
$this->middleList($this->root, $nodeList);
break;
case "last":
$this->lastList($this->root, $nodeList);
break;
default:
$this->frontList($this->root, $nodeList);
break;
}
return implode($nodeList);
}
//创建线索二叉树
public function createThreadTree(){
$this->headNode = new Node();
$this->preNode = & $this->headNode;
$this->headNode->setLTag(0);
$this->headNode->setLeft($this->root);
$this->headNode->setRTag(1);
$this->threadTraverse($this->root);
$this->preNode->setRight($this->headNode);
$this->preNode->setRTag(1);
$this->headNode->setRight($this->preNode);
}
//线索化二叉树
private function threadTraverse($node){
if($node != NULL){
if($node->getLeft() == NULL){
$node->setLTag(1);
$node->setLeft($this->preNode);
}else{
$this->threadTraverse($node->getLeft());
}
if($this->preNode != $this->headNode && $this->preNode->getRight() == NULL){
$this->preNode->setRTag(1);
$this->preNode->setRight($node);
}
$this->preNode = & $node;//注意传引用
$this->threadTraverse($node->getRight());
}
}
//从第一个结点遍历中序线索二叉树
public function threadList(){
$arr = array();
for($node = $this->getFirstThreadNode($this->root); $node != $this->headNode; $node = $this->getNextNode($node)){
$arr[] = $node->getData();
}
return implode($arr);
}
//从尾结点反向遍历中序线索二叉树
public function threadListReserv(){
$arr = array();
for($node = $this->headNode->getRight(); $node != $this->headNode; $node = $this->getPreNode($node)){
$arr[] = $node->getData();
}
return implode($arr);
}
//返回某个结点的前驱
public function getPreNode($node){
if($node->getLTag() == 1){
return $node->getLeft();
}else{
return $this->getLastThreadNode($node->getLeft());
}
}
//返回某个结点的后继
public function getNextNode($node){
if($node->getRTag() == 1){
return $node->getRight();
}else{
return $this->getFirstThreadNode($node->getRight());
}
}
//返回中序线索二叉树的第一个结点
public function getFirstThreadNode($node){
while($node->getLTag() == 0){
$node = $node->getLeft();
}
return $node;
}
//返回中序线索二叉树的最后一个结点
public function getLastThreadNode($node){
while($node->getRTag() == 0){
$node = $node->getRight();
}
return $node;
}
//前序遍历
private function frontList($node, & $nodeList){
if($node !== NULL){
$nodeList[] = $node->getData();
$this->frontList($node->getLeft(), $nodeList);
$this->frontList($node->getRight(), $nodeList);
}
}
//中序遍历
private function middleList($node, & $nodeList){
if($node != NULL){
$this->middleList($node->getLeft(), $nodeList);
$nodeList[] = $node->getData();
$this->middleList($node->getRight(), $nodeList);
}
}
//后序遍历
private function lastList($node, & $nodeList){
if($node != NULL){
$this->lastList($node->getLeft(), $nodeList);
$this->lastList($node->getRight(), $nodeList);
$nodeList[] = $node->getData();
}
}
public function getData(){
return $this->data;
}
public function getRoot(){
return $this->root;
}
}
?>
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