Home  >  Article  >  Backend Development  >  php implements queue

php implements queue

炎欲天舞
炎欲天舞Original
2018-05-10 14:28:3411358browse

Queue: Satisfies the first-in-first-out (FIFO) rule;

The following uses PHP to implement a simple circular queue model;

The initial state of the queue, the queue length is 0 , the pointers of the queue head and the queue tail are the same and both are located at the beginning of the queue;

Entering the queue operation: the queue tail pointer moves backward, and the length is increased by one;

Dequeuing operation: the queue head pointer moves to After moving, the length is reduced by one;

Features of circular queue: the queue size is fixed, the memory space opened by the queue can be recycled, the pointer is moved by the remainder operation with queueSize;

The following The example is to use an array to implement queue storage, and the array subscript is used as a pointer;

<?php


/**
 * Class Queue
 */
class Queue
{
    /**
     * @var int 队头指针
     */
    private $_front;

    /**
     * @var int 队尾指针
     */
    private $_rear;

    /**
     * @var array 队列数组
     */
    private $_queue;

    /**
     * @var int 队列实际长度
     */
    private $_queueLength;

    /**
     * @var int 队列容量;
     */
    private $_queueSize;

    /**
     * Queue constructor.初始化队列
     * @param int $capacity 容量(循环队列的最大长度)
     */
    public function __construct($size)
    {
        $this->_queue = [];
        $this->_queueSize = $size;
        $this->_front = 0;
        $this->_rear = 0;
        $this->_queueLength = 0;
    }

    /**
     * 销毁队列;
     */
    public function __destruct()
    {
        unset($this->_queue);
    }

    /**
     * @method 入队
     * @param mixed $elem 入队的元素
     * @return bool
     */
    public function enQueue($elem)
    {
        if (!$this->isFull()) {
            $this->_queue[$this->_rear] = $elem;
            $this->_rear++;
            $this->_rear = $this->_rear % $this->_queueCapacity;
            $this->_queueLength++;
            return true;
        }
        return false;
    }

    /**
     * @method 出队
     * @return mixed|null
     */
    public function deQueue()
    {
        if (!$this->isEmpty()) {
            $elem = $this->_queue[$this->_front];
            //unset($this->_queue[$this->_front]);
            $this->_front++;
            $this->_front %= $this->_queueCapacity;
            $this->_queueLength--;
            return $elem;
        }
        return null;
    }

    /**
     * @method 判断队列是否为空;
     * @return bool
     */
    public function isEmpty()
    {
        return $this->_queueLength === 0;
    }

    /**
     * @method 判断队列是否饱和;
     * @return bool
     */
    public function isFull()
    {
        return $this->_queueLength === $this->_queueCapacity;
    }

    /**
     * @method 遍历队列并输出(测试队列)
     */
    public function outputQueue()
    {
        for ($i = $this->_front; $i < $this->_queueLength + $this->_front; $i++) {
            echo $this->_queue[$i % $this->_queueCapacity].PHP_EOL;
        }
    }

    /**
     * @method 清空队列
     */
    public function clearQueue()
    {
        $this->_queue = [];
        $this->_front = 0;
        $this->_rear = 0;
        $this->_queueLength = 0;
    }
}

Test the queue class. Logically speaking, there is no big problem. Optimization depends on real business scenarios;

$a = new Queue(3);
echo &#39;enQueue1 $a->enQueue(1)&#39;.PHP_EOL;
$a->enQueue(1);
echo &#39;enQueue2 $a->enQueue(2)&#39;.PHP_EOL;
$a->enQueue(2);
echo &#39;enQueue3 $a->enQueue(3)&#39;.PHP_EOL;
$a->enQueue(3);
echo &#39;enQueue4 $a->enQueue(4)&#39;.PHP_EOL;
$a->enQueue(4);     //讲道理是失败的;
$a->outputQueue();      //输出 1 2 3
echo PHP_EOL;
echo PHP_EOL;
echo $a->deQueue();     //输出 1  队列 2 3
echo PHP_EOL;
echo PHP_EOL;
echo $a->deQueue();     //输出 2  队列 3
$a->enQueue(5);         //队列 3 5
echo PHP_EOL;
echo PHP_EOL;
$a->outputQueue();      //输出 3 5
$a->clearQueue();       //队列空;

The above is the detailed content of php implements queue. For more information, please follow other related articles on the PHP Chinese website!

Statement:
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Previous article:PHP classic algorithmNext article:PHP classic algorithm