(deque, full name double-ended queue) is a data structure with the properties of queue and stack. Elements in a two-way queue can be popped from both ends, and insertion and deletion operations are limited to both ends of the table.
In actual use, there can also be a two-way queue with limited output (that is, one endpoint allows insertion and deletion, A deque with the other endpoint allowing only insertions) and an input-restricted deque (i.e. a deque with one endpoint allowing insertions and deletions and the other endpoint allowing only deletions). And if the element inserted from a certain endpoint of the bidirectional queue is restricted to only be deleted from that endpoint, then the bidirectional queue will transform into two adjacent stacks at the bottom.
##DEQue.class.php
<?php
/** php 双向队列。支持限定队列长度，输入受限，输出受限，及输出必须与输入同端几种设置
* Date: 2014-04-30
* Author: fdipzone
* Ver: 1.0
*
* Func:
* public frontAdd 前端入列
* public frontRemove 前端出列
* public rearAdd 后端入列
* pulbic rearRemove 后端出列
* public clear 清空对列
* public isFull 判断对列是否已满
* private getLength 获取对列长度
* private setAddNum 记录入列,输出依赖输入时调用
* private setRemoveNum 记录出列,输出依赖输入时调用
* private checkRemove 检查是否输出依赖输入
*/
class DEQue{ // class start
private $_queue = array(); // 对列
private $_maxLength = 0; // 对列最大长度，0表示不限
private $_type = 0; // 对列类型
private $_frontNum = 0; // 前端插入的数量
private $_rearNum = 0; // 后端插入的数量
/** 初始化
* @param $type 对列类型
* 1:两端均可输入输出
* 2:前端只能输入，后端可输入输出
* 3:前端只能输出，后端可输入输出
* 4:后端只能输入，前端可输入输出
* 5:后端只能输出，前端可输入输出
* 6:两端均可输入输出，在哪端输入只能从哪端输出
* @param $maxlength 对列最大长度
*/
public function __construct($type=1, $maxlength=0){
$this->_type = in_array($type, array(1,2,3,4,5,6))? $type : 1;
$this->_maxLength = intval($maxlength);
}
/** 前端入列
* @param Mixed $data 数据
* @return boolean
*/
public function frontAdd($data=null){
if($this->_type==3){ // 前端输入限制
return false;
}
if(isset($data) && !$this->isFull()){
array_unshift($this->_queue, $data);
$this->setAddNum(1);
return true;
}
return false;
}
/** 前端出列
* @return Array
*/
public function frontRemove(){
if($this->_type==2){ // 前端输出限制
return null;
}
if(!$this->checkRemove(1)){ // 检查是否依赖输入
return null;
}
$data = null;
if($this->getLength()>0){
$data = array_shift($this->_queue);
$this->setRemoveNum(1);
}
return $data;
}
/** 后端入列
* @param Mixed $data 数据
* @return boolean
*/
public function rearAdd($data=null){
if($this->_type==5){ // 后端输入限制
return false;
}
if(isset($data) && !$this->isFull()){
array_push($this->_queue, $data);
$this->setAddNum(2);
return true;
}
return false;
}
/** 后端出列
* @return Array
*/
public function rearRemove(){
if($this->_type==4){ // 后端输出限制
return null;
}
if(!$this->checkRemove(2)){ // 检查是否依赖输入
return null;
}
$data = null;
if($this->getLength()>0){
$data = array_pop($this->_queue);
$this->setRemoveNum(2);
}
return $data;
}
/** 清空对列
* @return boolean
*/
public function clear(){
$this->_queue = array();
$this->_frontNum = 0;
$this->_rearNum = 0;
return true;
}
/** 判断对列是否已满
* @return boolean
*/
public function isFull(){
$bIsFull = false;
if($this->_maxLength!=0 && $this->_maxLength==$this->getLength()){
$bIsFull = true;
}
return $bIsFull;
}
/** 获取当前对列长度
* @return int
*/
private function getLength(){
return count($this->_queue);
}
/** 记录入列,输出依赖输入时调用
* @param int $endpoint 端点 1:front 2:rear
*/
private function setAddNum($endpoint){
if($this->_type==6){
if($endpoint==1){
$this->_frontNum ++;
}else{
$this->_rearNum ++;
}
}
}
/** 记录出列,输出依赖输入时调用
* @param int $endpoint 端点 1:front 2:rear
*/
private function setRemoveNum($endpoint){
if($this->_type==6){
if($endpoint==1){
$this->_frontNum --;
}else{
$this->_rearNum --;
}
}
}
/** 检查是否输出依赖输入
* @param int $endpoint 端点 1:front 2:rear
*/
private function checkRemove($endpoint){
if($this->_type==6){
if($endpoint==1){
return $this->_frontNum>0;
}else{
return $this->_rearNum>0;
}
}
return true;
}
} // class end
?>demo.php
<?php require "DEQue.class.php"; // 例子1 $obj = new DEQue(); // 前后端都可以输入，无限长度 $obj->frontAdd('a'); // 前端入列 $obj->rearAdd('b'); // 后端入列 $obj->frontAdd('c'); // 前端入列 $obj->rearAdd('d'); // 后端入列 // 入列后数组应为 cabd $result = array(); $result[] = $obj->rearRemove(); // 后端出列 $result[] = $obj->rearRemove(); // 后端出列 $result[] = $obj->frontRemove(); // 前端出列 $result[] = $obj->frontRemove(); // 前端出列 print_r($result); // 出列顺序应为 dbca // 例子2 $obj = new DEQue(3, 5); // 前端只能输出，后端可输入输出，最大长度5 $insert = array(); $insert[] = $obj->rearAdd('a'); $insert[] = $obj->rearAdd('b'); $insert[] = $obj->frontAdd('c'); // 因前端只能输出，因此这里会返回false $insert[] = $obj->rearAdd('d'); $insert[] = $obj->rearAdd('e'); $insert[] = $obj->rearAdd('f'); $insert[] = $obj->rearAdd('g'); // 超过长度，返回false var_dump($insert); // 例子3 $obj = new DEQue(6); // 输出依赖输入 $obj->frontAdd('a'); $obj->frontAdd('b'); $obj->frontAdd('c'); $obj->rearAdd('d'); $result = array(); $result[] = $obj->rearRemove(); $result[] = $obj->rearRemove(); // 因为输出依赖输入，这个会返回NULL $result[] = $obj->frontRemove(); $result[] = $obj->frontRemove(); $result[] = $obj->frontRemove(); var_dump($result); ?>
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