隊(duì)列(Queue)是插入操作限定在表的尾部而其它操作限定在表的頭部進(jìn)行的線(xiàn)性表。把進(jìn)行插入操作的表尾稱(chēng)為隊(duì)尾(Rear)，把進(jìn)行其它操作的頭部稱(chēng)為隊(duì)頭(Front)。當(dāng)對(duì)列中沒(méi)有數(shù)據(jù)元素時(shí)稱(chēng)為空對(duì)列(Empty Queue)。

隊(duì)列通常記為：Q= (a1,a2,…,an)，a1為隊(duì)頭元素，an為隊(duì)尾元素。元素按照a1,a2,…,an的次序依次入隊(duì)，出隊(duì)的次序與入隊(duì)相同，即a1第一個(gè)出隊(duì)，an最后一個(gè)出隊(duì)。所以，對(duì)列的操作是按照先進(jìn)先出(First In First Out)或后進(jìn)后出( Last In Last Out)的原則進(jìn)行的，因此，隊(duì)列又稱(chēng)為FIFO表或LILO表。

隊(duì)列的常用操作有：

1、構(gòu)造一個(gè)空隊(duì)列：InitQueue()//在C#中可以使用構(gòu)造函數(shù)來(lái)實(shí)現(xiàn)

2、清空隊(duì)列：ClearQueue()

3、判斷隊(duì)列是否為空：IsEmpty()

4、判斷隊(duì)列是否已滿(mǎn)：IsFull()

5、求隊(duì)列長(zhǎng)度：QueueLength()

6、入隊(duì)操作：In()

7、出隊(duì)操作：Out()

8、得到隊(duì)頭元素：GetHead()

下面給出一個(gè)實(shí)現(xiàn)順序棧的源代碼：

using System;

class Queue

{

    object[] data;  //數(shù)據(jù)元素

    int maxsize;    //最大容量

    int front;      //指向隊(duì)頭

    int rear;       //指向隊(duì)尾

    //初始化隊(duì)列

    public Queue(int size)

    {

        this.maxsize = size;

        data = new object[size];

        front = rear = -1;

    }

    //最大容量屬性

    public int MaxSize

    {

        get

        {

            return this.maxsize;

        }

        set

        {

            this.maxsize = value;

        }

    }

    //隊(duì)尾屬性

    public int Rear

    {

        get

        {

            return this.rear;

        }

    }

    //隊(duì)頭屬性

    public int Front

    {

        get

        {

            return this.front;

        }

    }

    //數(shù)據(jù)屬性

    public object this[int index]

    {

        get

        {

            return data[index];

        }

    }

    //獲得隊(duì)列的長(zhǎng)度

    public int GetQueueLength()

    {

        return rear-front;

    }

    //判斷隊(duì)列是否滿(mǎn)

    public bool IsFull()

    {

        if(GetQueueLength() == maxsize)

            return true;

        else

            return false;

    }

    //判斷隊(duì)列是否為空

    public bool IsEmpty()

    {

        if(rear==front)

            return true;

        else

            return false;

    }

    //清空隊(duì)列

    public void ClearQueue()

    {

        rear = front = -1;

    }

    //入隊(duì)

    public void In(object e)

    {

        if(IsFull())

        {

            Console.WriteLine("隊(duì)列已滿(mǎn)！");

            return;

        }

        data[++rear]=e;

    }

    //出隊(duì)

    public object Out()

    {

        if(IsEmpty())

        {

            Console.WriteLine("隊(duì)列為空！");

            return null;

        }

        if(rear-front>0)

        {

            object tmp = data[++front];

            return tmp;

        }

        else

        {

            Console.WriteLine("全出隊(duì)了！");

            ClearQueue();

            return null;

        }

    }

    //獲得隊(duì)頭元素

    public object GetHead()

    {

        if(IsEmpty())

        {

            Console.WriteLine("隊(duì)列為空！");

            return null;

        }

        return data[front+1];

    }

}

class Test

{

    static void Main()

    {

        Queue q = new Queue(1);

        int rdNum;

        Random rd = new Random();

        while(!q.IsFull())

        {

            rdNum = rd.Next(10,100);

            q.In(rdNum);

            Console.WriteLine("{0}入隊(duì),隊(duì)列元素個(gè)數(shù)：{1}",rdNum,q.GetQueueLength());