簡述

• front 指向隊首元素，rear-1 指向隊尾元素
• 佇列最大長度：MAXSIZE
• 隊列當前長度：count = (rear - front + MAXSIZE) % MAXSIZE
• 佇列空：front == rear
• 佇列滿：(rear + 1) % MAXSIZE == front（**此時佇列中元素個數為 MAXSIZE–即有一個空閒元素，具體如下圖所示）
• 初始狀態下，front = rear = 0

程式碼：

using System;

interface IQueue<T>
{
    int
 
 Count{get;}
    int GetLength();
    bool IsEmpty();
    void Clear();
    void EnQueue(T element);
    T DeQueue();
    T Peek();
}

class SeqQueue<T> : IQueue<T>
{
    private int MAXSIZE;
    private T[] data;
    int front;
    int rear;

    public SeqQueue(int size)
    {
        MAXSIZE = size;
        data = new
 
 T[size];
        front = 0;//data[front+1] is hear element
        rear = 0;
    }
    public SeqQueue() : this(10)
    {
    }

    public int Count{get{return (rear - front + MAXSIZE) % MAXSIZE;}}
    public int GetLength()
    {
        return (rear - front + MAXSIZE) % MAXSIZE;
    }
    public bool
 
 IsEmpty()
    {
        return front == rear;
    }
    public void Clear()
    {
        front = -1;
        rear = -1;
    }
    public void EnQueue(T value)
    {
        if((rear + 1) % MAXSIZE == front)
        {Console.WriteLine("SeqQueue is full, can not EnQueue"); return;}
        //loop, so EnQueue at end is to EnQueue at start
        data[rear] = value;
        rear =(rear+1) % MAXSIZE;
    }
    public T DeQueue()
    {
        T value = default(T);
        if(IsEmpty())
        {
            Console.WriteLine("SeqQueue is Empty, can not DeQueue");
            return value;
        }
        else
        {
            value = data[front];
            //loop
            front = (front+1) % MAXSIZE;
            return value;
        }
    }
    public T Peek()
    {
        return data[front];
    }
}


public class Test
{
    public static void Main()
    {
        IQueue<string> queue = new SeqQueue<string>();

        queue.EnQueue("aaa");
        queue.EnQueue("bbb");
        queue.EnQueue("ccc");

        Console.WriteLine("push aaa bbb ccc, queue.Count:{0}", queue.Count);
        Console.WriteLine("queue.Peek:{0}", queue.Peek());
        while(queue.Count > 0)
        {
            Console.WriteLine("queue.DeQueue:{0}", queue.DeQueue());
        }
    }
}

執行結果：

push aaa bbb ccc, queue.Count:3
queue.Peek:aaa
queue.DeQueue:aaa
queue.DeQueue:bbb
queue.DeQueue:ccc