C++数据结构之链式队列（Linked Queue）

C++数据结构之链式队列，实现的基本思想和链式栈的实现差不多，比较不同的一点也是需要注意的一点是，链式队列的指向指针有两个，一个是队头指针（front），一个是队尾指针（rear），注意指针的指向是从队首指到队尾（front -> Front_Node -> …… -> rear -> Rear_Node）.

代码：

Node.h文件

/*
 * Node.h
 *
 *  Created on: 2015年9月10日
 *      Author: Lv_Lang
 */

#ifndef NODE_H_
#define NODE_H_

#include "stdio.h" 	// for NULL

typedef int Queue_entry;
typedef Queue_entry Node_entry;

struct Node
{
	//	data members
	Node_entry entry; // 存放的元素
	Node *next;		  // 指向下一个元素的指针
	//	Constructors
	Node();
	Node(Node_entry item, Node *add_on = NULL);
};

#endif /* NODE_H_ */

Node.cpp文件：

/*
 * Node.cpp
 *
 *  Created on: 2015年9月10日
 *      Author: Lv_Lang
 */
#include "Node.h"

Node::Node()
{
	next = NULL;
}
Node::Node(Node_entry item, Node *add_on)
{
	entry = item;
	next = add_on;
}

Queue.h文件：

/*
 * Queue.h
 *
 *  Created on: 2015年9月10日
 *      Author: Lv_Lang
 */

#ifndef QUEUE_H_
#define QUEUE_H_

#include "stdio.h"
#include "Node.h"
enum Error_code {overflow,underflow,success};

class Queue
{
public:
//  Standard Queue methods
	Queue();
	bool empty()const;
	Error_code append(const Queue_entry &item);
	Error_code serve();
	Error_code retrieve(Queue_entry &item)const;
//	Safety features for linked structures
	~Queue();
	Queue(const Queue &original);
	void operator = (const Queue &original);
//  Extended linked queue
	bool full()const;
	int size()const;
	void clear();
protected:
	Node *front, *rear;
};

#endif /* QUEUE_H_ */

Queue.cpp文件

/*
 * Queue.cpp
 *
 *  Created on: 2015年9月10日
 *      Author: Lv_Lang
 */
#include "Queue.h"

Queue::Queue()
{
	front = NULL;
	rear = NULL;
}
bool Queue::empty()const
{
	if((front == NULL) && (rear == NULL))
		return true;
	else
		return false;
}
Error_code Queue::append(const Queue_entry &item)
{
	Node *new_rear = new Node(item);
	if(new_rear == NULL)
		return overflow;
	if(rear == NULL) front = rear = new_rear;
	else
	{
		rear->next = new_rear;
		rear = new_rear;
	}
	return success;
}
Error_code Queue::serve()
{
	if(empty())
		return underflow;
	else
	{
		Node *old_front = front;
		front = front->next;
		if(front == NULL) rear = NULL;// 此处需注意将rear也置为0
		delete	old_front;
		return success;
	}
}
Error_code Queue::retrieve(Queue_entry &item)const
{
	if(empty())
			return underflow;
	else
	{
		item = front->entry;
		return success;
	}
}
Queue::~Queue()
{
	if(!empty())
	{
		serve();
	}
}
Queue::Queue(const Queue &original)
{
	Node *new_front, *original_front = original.front;
	if(original.front == NULL)
		front = rear= NULL;
	else
	{
		front = new_front = new Node(original_front->entry);
		while(original_front->next != NULL)
		{
			original_front = original_front->next;
			new_front->next = new Node(original_front->entry);
			new_front = new_front->next;
		}
	}
}
void Queue::operator =(const Queue &original)
{
	Node *new_front, *original_front = original.front;
	if(original.front == NULL)
		front = rear= NULL;
	else
	{
		if(!empty())
			clear();
		else
		{
			front = new_front = new Node(original_front->entry);
			while(original_front->next != NULL)
			{
				original_front = original_front->next;
				new_front->next = new Node(original_front->entry);
				new_front = new_front->next;
			}
		}
	}
}
bool Queue::full()const
{
	Node *new_front = new Node();
	if(new_front == NULL)
<span style="white-space:pre">	</span>{		

<span style="white-space:pre">		delete new_front;</span>

<span style="white-space:pre">		</span>return true;

<span style="white-space:pre">	</span>}
	else
	{
		delete new_front;
		return false;
	}
}
int Queue::size()const
{
	Node *window = front;
	int count = 0;
	while(window != NULL)
	{
		window = window->next;
		count++;
	}
	return count;
}
void Queue::clear()
{
	if(!empty())
	{
		serve();
	}
}

main函数测试文件：

/*
 * main.cpp
 *
 *  Created on: 2015年9月10日
 *      Author: Lv_Lang
 */
#include "Queue.h"

int main()
{
	Queue myqueue;
	myqueue.append(2);
	myqueue.append(6);
	int size;
	size = myqueue.size();
	printf("%s %d\n","Size is ",size);
	myqueue.serve();
	int a;
	myqueue.retrieve(a);
	printf("%d\n",a);
	size = myqueue.size();
	printf("%s %d\n","Size is ",size);

	Queue QUEUE(myqueue);
	int b;
	QUEUE.retrieve(b);
	printf("%d\n",b);
	size = QUEUE.size();
	printf("%s %d\n","Size for QUEUE is ",size);

	myqueue.clear();
	size = myqueue.size();
	printf("%s %d\n","Size is ",size);

	return 0;
}