Example of implementing two-way queue in php

Briefly introduce that in actual use, there can also be a two-way queue with limited output (that is, a two-way queue with one endpoint allowing insertion and deletion, and the other endpoint only allowing insertion) and a two-way queue with limited input (that is, one endpoint A deque that allows insertions and deletions, the other endpoint only allows deletions). 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.

1. One-way queue: can only enter from the beginning and exit from the tail
2. Two-way queue: both the head and tail can enter and exit

<?php
    class duilie{
        private $arr=array();        //从头进
        public function Head_in($item){
            return array_unshift($this->arr,$item);
        }        //从头出
        public function Head_out(){
            return array_shift($this->arr);
        }        //从尾进
        public function Tail_in($item){
            return array_push($this->arr,$item);
        }        //从尾出
        public function Tail_out(){
            return array_pop($this->arr);
        }        //清空队列
        public function clear(){
            unset($this->arr);
        }        //显示队列
        public function show(){
            return implode(&#39; &#39;,$this->arr);
        }        //获得队列队尾的值
        public function get_last(){
            return array_pop($this->arr);
        }        //获得队列队首的值
        public function get_first(){
            return array_shift($this->arr);
        }
    }    $obj=new duilie();    $obj->Tail_in(&#39;a&#39;);    $obj->Head_in(&#39;b&#39;);    $obj->Head_in(&#39;c&#39;);    $obj->Tail_out();    $arr=$obj->show();    echo $arr;?>

1.  One-way Queue: You can only enter from the beginning and exit from the tail
2. Two-way queue: Both the head and tail can enter and exit

<?php
    class duilie{
        private $arr=array();        //从头进
        public function Head_in($item){
            return array_unshift($this->arr,$item);
        }        //从头出
        public function Head_out(){
            return array_shift($this->arr);
        }        //从尾进
        public function Tail_in($item){
            return array_push($this->arr,$item);
        }        //从尾出
        public function Tail_out(){
            return array_pop($this->arr);
        }        //清空队列
        public function clear(){
            unset($this->arr);
        }        //显示队列
        public function show(){
            return implode(&#39; &#39;,$this->arr);
        }        //获得队列队尾的值
        public function get_last(){
            return array_pop($this->arr);
        }        //获得队列队首的值
        public function get_first(){
            return array_shift($this->arr);
        }
    }    $obj=new duilie();    $obj->Tail_in(&#39;a&#39;);    $obj->Head_in(&#39;b&#39;);    $obj->Head_in(&#39;c&#39;);    $obj->Tail_out();    $arr=$obj->show();    echo $arr;?>

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How to use PHP to implement a two-way queue code example

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