The example in this article describes the two-way queue class implemented in PHP and its usage. It has a good reference value for learning PHP data structures and algorithms. Share it with everyone for your reference. The specific analysis is as follows:
(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 output-limited bidirectional queues (i.e., one endpoint allows insertion and deletion, and the other endpoint only allows insertions) and input-limited bidirectional queues (i.e., one endpoint allows insertion and deletion) delete, the other endpoint only allows deletion of the deque). And if the elements inserted from a certain endpoint of the bidirectional queue can only be deleted from that endpoint, then the bidirectional queue will transform into two adjacent stacks at the bottom.
DEQue.class.php class file is as follows:
<?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 sample code is as follows:
<?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);
?>
Click here to download the complete example code from this website.
I hope this article will be helpful to everyone’s study of PHP program algorithm design.
Unknown problem
class queue{
private $q = array();
public function push($v){
array_push($this -> q, $v);
}
public function shift(){
return shift($this -> q);
}
}
The simplest queue.
However, don’t you feel a bit overwhelmed using PHP to implement data structures?
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