linked queue.cpp

链式队列

#include "linked queue.h"
#include "node.h"

Linkedqueue::Linkedqueue()
{
	front=NULL;
}
/****************************************************/
Error_code Linkedqueue::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 Linkedqueue::serve()
{
	if (front==NULL)
	{
		return underflow;
	}
	Node *old_front=front;
	front=old_front->next;
	if (front==NULL)
	{
		rear=NULL;
	}
    delete old_front;
	return success;
}
/****************************************************/
Error_code Linkedqueue::retrieve(Queue_entry &item)const
{
	if (front==NULL)
	{
		return underflow;
	}
	item=front->entry;
	return success;
}
/****************************************************/
bool Linkedqueue::empty()const
{
	if (front==NULL)
	{
		return true;
	}
	else
	{
		return false;
	}
}
/****************************************************/
Linkedqueue::~Linkedqueue()
{
	while (!empty())
	{
		serve();
	}
}
/****************************************************/
Linkedqueue::Linkedqueue(const Linkedqueue &original)
{
	Node *new_copy,*original_node=original.front;
	if (original_node==NULL)
	{
		front=NULL;
	}
	else
	{
		front=new_copy=new Node(original_node->entry);
		while(original_node->next!=NULL)
		{
			original_node=original_node->next;
			new_copy->next=new Node(original_node->entry);
			new_copy=new_copy->next;
		}
	}
}
/****************************************************/
void Linkedqueue::operator=(const Linkedqueue &original)
{
	Node *new_front,*new_copy,*original_node=original.front;
	if (original_node==NULL)
	{
		new_front=NULL;
	}
	else
	{
		new_front=new_copy=new Node(original_node->entry);
		while(original_node->next!=NULL)
		{
			original_node=original_node->next;
			new_copy->next=new Node(original_node->entry);
			new_copy=new_copy->next;
		}
	}
	while (!empty())
	serve();
	front=new_front;
}
/*****************************************************/