第三十六课 队列的概念及实现（上）

 

 

 使用循环计数法的目的是为了高效。

 添加Queue.h文件：

#ifndef QUEUE_H
#define QUEUE_H

#include "Object.h"

namespace DTLib
{

template < typename T >
class Queue : public Object
{
public:
    virtual void add(const T& e) = 0;
    virtual void remove() = 0;
    virtual T front() const = 0;
    virtual void clear() = 0;
    virtual int length() const = 0;
};

}

#endif // QUEUE_H

添加StaticQueue.h文件：

#ifndef STATICQUEUE_H
#define STATICQUEUE_H

#include "Queue.h"
#include "Exception.h"

namespace DTLib
{

template < typename T, int N >
class StaticQueue : public Queue<T>
{
protected:
    T m_space[N];
    int m_front;
    int m_rear;
    int m_length;
public:
    StaticQueue()
    {
        m_front = 0;
        m_rear = 0;
        m_length = 0;
    }

    int capacity() const
    {
        return N;
    }

    void add(const T& e)
    {
        if( m_length < N )
        {
            m_space[m_rear] = e;
            m_rear = (m_rear + 1) % N;
            m_length++;
        }
        else
        {
            THROW_EXCEPTION(InvalidOperationException, "No space in current queue...");
        }
    }

    void remove()
    {
        if( m_length > 0 )
        {
            m_front = (m_front + 1) % N;
            m_length--;
        }
        else
        {
            THROW_EXCEPTION(InvalidOperationException, "No element in current queue...");
        }
    }

    T front() const
    {
        if( m_length > 0 )
        {
            return m_space[m_front];
        }
        else
        {
            THROW_EXCEPTION(InvalidOperationException, "No element in current queue...");
        }
    }

    void clear()
    {
        m_front = 0;
        m_rear = 0;
        m_length = 0;
    }

    int length() const
    {
        return m_length;
    }

    ~StaticQueue()
    {
        clear();
    }
};

}

#endif // STATICQUEUE_H

测试程序如下：

#include <iostream>
#include "StaticQueue.h"

using namespace std;
using namespace DTLib;


int main()
{
    StaticQueue<int, 5> queue;

    for(int i = 0; i < 5; i++)
    {
        queue.add(i);
    }

    while( queue.length() > 0 )
    {
        cout << queue.front() << endl;

        queue.remove();
    }

    return 0;
}

运行结果如下：

小结：