使用不带头结点的循环链表实现队列（数据结构）

我们来分析。尾部push数据的时候，我们仅仅须要在myback和myback->next之间插入这个结点。然后把这个myback指向这个结点就可以。取出和删除头部数据仅仅须要对myback->next进行操作就可以，复杂度是O（1），效率非常高。

剩下的一些实现细节看我以下的代码实现：

//circle_list.h
#ifndef CIRCLE_LIST
#define CIRCLE_LIST
#include<iostream>
#include<string>
#include<cstring>
template <typename T>
class node//节点类
{
public:
	T data;
	node *next;
	node(T da = 0, node *n = NULL) :data(da), next(n){}
};
template <typename T>
class Queue
{
public:
	node<T> *myback;
	int size;
	Queue(node<T> *begin = NULL, int s = 0) :myback(begin),size(s){}
	bool empty();
	void enqueue(T value);//后面压入
	T front();
	void display();
	void dequeue();//前面删除
	~Queue();
	Queue(const Queue<T> &temp);
	Queue<T> operator=(const Queue<T>temp);
};
template <typename T>
bool Queue<T>::empty()
{
	if (size == 0)
		return true;
	return false;
}
template <typename T>
Queue<T>::Queue(const Queue<T> &temp)
{
		size = 0;
		node<T>* scan = (temp.myback)->next;
		while (scan != temp.myback)
		{
			enqueue(scan->data);
			scan = scan->next;
		}
		enqueue(temp.myback->data);

}
template <typename T>
Queue<T> Queue<T>::operator=(const Queue<T> temp)
{

		size = 0;
		node<T>* scan = (temp.myback)->next;
		while (scan != temp.myback)
		{
			enqueue(scan->data);
			scan = scan->next;
		}
		enqueue(temp.myback->data);
	return *this;
}


template <typename T>
void Queue<T>::enqueue(T value)
{

	node<T>*last = new node<T>;
	last->data = value;
	if (size == 0)
	{
		myback = last;
		myback->next = myback;
	}
	else
	{
		node<T> *temp = myback->next;
		myback->next = last;
		last->next = temp;
		myback = last;
		myback->next = temp;
	}
	size++;
}
template <typename T>
T Queue<T>::front()
{
	return (myback->next)->data;
}
template <typename T>
void Queue<T>::display()
{
	if (size == 1)
	{
		cout << myback->data << endl;
		return;
	}
	else
	{
		node<T> *first = myback->next;
		while (first != myback)
		{
			cout << first->data << " ";
			first = first->next;
		}
		cout << myback->data;
		cout << endl;
	}
}
template <typename T>
void Queue<T>::dequeue()
{

	node<T>*cur = myback->next;
	node <T>*now = cur->next;
	myback->next = now;
	delete cur;
	size--;
}
template <typename T>
Queue<T>::~Queue()
{
	if (size == 0){}
	else
	{
		node<T> *p = myback->next;
		node<T> *nex = p->next;
		while (p != myback)
		{
			delete p;
			p = nex;
			nex = nex->next;
		}
		delete myback;
	}
}

#endif

进行測试：

//main.cpp
#include"circle_list.h"
using namespace std;
int main()
{
	Queue<int> q;
	cout <<"队列是否为空？"<< q.empty() << endl;
	q.enqueue(1);
	q.enqueue(2);
	q.enqueue(3);
	cout << "输出第一个队列中的数据：" << endl;
	q.display();
	Queue<int> a(q);
	cout << "输出通过拷贝构造函数建立的队列中的数据：" << endl;
	a.display();
	Queue<int> b;
	b = q; cout << "输出通过赋值运算符重载建立的队列中的数据：" << endl;
	b.display();
	cout << "输出队列首的元素：" << endl;
	cout << q.front() << endl;
	q.dequeue();
	cout << "删除队首元素后的队列：" << endl;
	q.display();
	//cout << q.empty() << endl;
	return 0;
}

实验结果截图;