数据结构之队列――链式存储结构（php代码实现）

<?php

class QNode{
public  $data;
public  $next;
public function __construct($data){
$this->data=$data;
$this->next=null;
}
}

class LinkQueue{ //链队列包含头结点,实例化时，此队列为空
private $data;
private $next;
private $front;//指向头结点
private $rear;//指向尾结点
//    private $length;
public function __construct(){
$this->data=null;
$this->next=null;
$this->front=$this; //指向头结点
$this->rear=$this;//指向头结点
//        $this->length=0;
}

//销毁队列
public function DestroyQueue(){
while($this->front){ //销毁首先是从头结点开始
$this->rear=$this->front->next;
unset($this->front);
$this->front=$this->rear;
}
}

//清空队列
public function ClearQueue(){
$p=$this->front->next;
while($p){
$q=$p->next;
unset($p);
$p=$q;
}
$this->front->next=null;
$this->rear=$this->front;
}

//队列是否为空
public function QueueEmpty(){
if($this->front==$this->rear){
return 'Null';
}else{
return 'No Null';
}
}

//队列的长度
public function QueueLength(){
$p=$this->front;
$i=0;
while($p != $this->rear){
$i++;
$p=$p->next;
}
return $i;
//        return $this->length;
}

//取得队头元素
public function GetHead(){
if($this->front==$this->rear){
return 'ERROR';
}
return $this->front->next->data;
}

//从队尾插入元素
public function EnQueue(){
$node=new QNode(mt_rand(100,200));
$node->next=$this->rear->next;
$this->rear->next=$node;
$this->rear=$node;
$this->length++;
}

//从队头删除元素
public function DeQueue(){
if($this->front==$this->rear){
return 'ERROR';
}
$p=$this->front->next;
unset($this->front->next);
$this->front->next=$p->next;

if($this->rear==$p){ //如果只有一个元素那么，为指针就需要变化了。
$this->rear=$this->front;
}
$this->length--;
return 'OK';
}

//遍历队列元素
public function QueueTraverse(){
if($this->front==$this->rear){
return 'ERROR';
}

$arr=array();
$p=$this->front->next;
while($p){
$arr[]=$p->data;
$p=$p->next;
}
return $arr;
}
}