About PHP two-way Queue class explanation

(deque, full name double-ended queue) is a data structure that has the nature of queues and stacks. Elements in a two-way queue can be ejected from both ends, and their qualified insert and delete operations are performed at both ends of the table.

In practice, you can also have output-constrained bidirectional queues (that is, one endpoint allows insertions and deletions, the other endpoint allows only two bidirectional queues to be inserted) and a restricted bidirectional queue (that is, one endpoint allows insertions and deletions, and the other endpoint allows only two-way queues to be deleted). If an element that qualifies a bidirectional queue to be inserted from an endpoint can only be removed from that endpoint, the bidirectional queue is transformed into a stack of two stacks that are adjacent to the bottom of the stack.

DEQue.class.php

<?php/** php bidirectional queue.     Support limit queue Length, input restricted, output limited, and output must be in the same port with the input several settings * date:2014-04-30* author:fdipzone* ver:1.0** func:* public Frontadd Front into row * Public frontremove front-end dequeue * Public Rearadd backend into row * pulbic Rearremove Backend dequeue * Public clear empty Pair Column * Public isfull determines whether the column is full * Private getlength gets the column length * Private setaddnum entry column, output dependent input call * Private Setrem    Ovenum record dequeue, output dependent input when called * private checkremove Check output dependent input */class deque{//class start Private $_queue = Array ();//Pair column   Private $_maxlength = 0;        For the maximum column length, 0 means no limit to private $_type = 0;    To column type private $_frontnum = 0;     Number of front-end inserts private $_rearnum = 0; Number of back-end inserts/** Initialize * @param $type to column type * 1: Both ends can be input and output * 2: Front-end can only be entered, the backend may be Input/Output * 3: Front-end only output, back-end can be input and output * 4: Back-end can only input, front-end can be input and output * 5: Back-end only output, front-end  Input/output * 6: Both ends can be input and output, at which end the input can only output from which side * @param $maxlength to the maximum length of the column * *  Public function __construct ($type =1, $maxlength =0) {$this->_type = In_array ($type, Array (1,2,3,4,5,6))? $type        : 1;    $this->_maxlength = intval ($maxlength); }/** front into row * @param Mixed $data Data * @return Boolean */Public function Frontadd ($data =null) {if (        $this->_type==3) {//Front-end input limit return false;            } if (Isset ($data) &&! $this->isfull ()) {Array_unshift ($this->_queue, $data);            $this->setaddnum (1);        return true;    } return false;            /** Front-end dequeue * @return Array */Public Function Frontremove () {if ($this->_type==2) {//front-end output limit        return null;        } if (! $this->checkremove (1)) {//check whether the input return null is dependent;        } $data = null;            if ($this->getlength () >0) {$data = Array_shift ($this->_queue);        $this->setremovenum (1);    } return $data; }/** back end into row * @parAM Mixed $data Data * @return Boolean */Public function Rearadd ($data =null) {if ($this->_type==5) {//        Back-end input limit return false;            } if (Isset ($data) &&! $this->isfull ()) {Array_push ($this->_queue, $data);            $this->setaddnum (2);        return true;    } return false;            }/** back-end dequeue * @return Array */Public Function Rearremove () {if ($this->_type==4) {//back-end output limit        return null;        } if (! $this->checkremove (2)) {//check whether the input return null is dependent;        } $data = null;            if ($this->getlength () >0) {$data = Array_pop ($this->_queue);        $this->setremovenum (2);    } return $data;        /** Empty the column * @return Boolean */Public Function Clear () {$this->_queue = array ();        $this->_frontnum = 0;        $this->_rearnum = 0;    return true; }/** Determines whether the column is full * @return Boolean */Public Function Isfull () {$bIsFull = false;        if ($this->_maxlength!=0 && $this->_maxlength== $this->getlength ()) {$bIsFull = true;    } return $bIsFull;    /** gets the current pair of column lengths * @return int */Private Function GetLength () {return count ($this->_queue);        }/** input column, call * @param int $endpoint endpoint 1:front 2:rear */Private Function Setaddnum ($endpoint) when output dependent inputs {            if ($this->_type==6) {if ($endpoint ==1) {$this->_frontnum + +;            }else{$this->_rearnum + +; }}}/** records a dequeue, the output depends on input when called * @param int $endpoint endpoint 1:front 2:rear */Private Function Setremovenum ($            Endpoint) {if ($this->_type==6) {if ($endpoint ==1) {$this->_frontnum--;            }else{$this->_rearnum--; }}}/** check if output dependent input * @param int $endpoint endpoint 1:front 2:rear */PrivaTe function Checkremove ($endpoint) {if ($this->_type==6) {if ($endpoint ==1) {return $thi            s->_frontnum>0;            }else{return $this->_rearnum>0;    }} return true; }}//Class end?>

demo.php

<?phprequire "DEQue.class.php";//Example 1$obj = new DEQue (); Both front and rear end can be input, infinite length $obj->frontadd (' a ');  Front end into row $obj->rearadd (' B '); Back end into row $obj->frontadd (' C ');  Front end into row $obj->rearadd (' d '); After the backend into row//into row the array should be Cabd$result = Array (); $result [] = $obj->rearremove (); Back-end dequeue $result[] = $obj->rearremove (); Back-end dequeue $result[] = $obj->frontremove (); Front-end dequeue $result[] = $obj->frontremove (); Front-end dequeue Print_r ($result); The dequeue order should be dbca//example 2$obj = new DEQue (3, 5); The front end can only output, the back end is input and output, the maximum length 5$insert = Array (), $insert [] = $obj->rearadd (' a '), $insert [] = $obj->rearadd (' B '); $insert [ ] = $obj->frontadd (' C '); Because the front end can only output, this returns false$insert[] = $obj->rearadd (' d '), $insert [] = $obj->rearadd (' e '); $insert [] = $obj Rearadd (' f '); $insert [] = $obj->rearadd (' G '); Over length, return falsevar_dump ($insert);//Example 3$obj = new DEQue (6); Output dependent input $obj->frontadd (' a '), $obj->frontadd (' B '), $obj->frontadd (' C '); $obj->rearadd (' d '); $result = Array (); $result [] = $obj->rearremove (); $result [] = $obj-&Gt;rearremove (); Because the output depends on the input, this returns null$result[] = $obj->frontremove (); $result [] = $obj->frontremove (); $result [] = $obj Frontremove (); Var_dump ($result);? >

This article explains the PHP bidirectional queue class, more relevant content please focus on PHP Chinese web.

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