链式队列

#ifndef QUEUELI_H
#define QUEUELI_H

template<class Object>
class Queue
{
public:
Queue();
~Queue();

bool isEmpty() const;
const Object & getFront() const;
void enqueue(const Object & x);
Object dequeue();
void makeEmpty();

private:
struct ListNode  //这里的struct不知道为啥不能够换成class，换成class有错误，
{
Object element; // 这个是节点里边的数据，
ListNode *next;
ListNode(const Object & theElement,ListNode *n = 0)
: element(theElement), next(n) {}
};
ListNode *front;
ListNode *back;
};

template<class Object>
Queue<Object>::Queue()
{
front = back = 0;
}

template<class Object>
Queue<Object>::~Queue()
{
makeEmpty();
}

template<class Object>
void Queue<Object>::makeEmpty()
{
while(!isEmpty())
dequeue();
}

template<class Object>
bool Queue<Object>::isEmpty() const
{
return front == 0;
}

template<class Object>
const Object & Queue<Object>::getFront() const
{
if(isEmpty())
throw "Queue is empty.";
return front->element;
}

template<class Object>
void Queue<Object>::enqueue(const Object &x)
{
if(isEmpty())
back = front = new ListNode(x);
else
back = back->next = new ListNode(x);
}

template<class Object>
Object Queue<Object>::dequeue()
{
Object frontItem = getFront();
ListNode *old = front;
front = front->next;
delete old;

return frontItem;
}

#endif

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

using namespace std;

int main()
{
Queue<int> myQ;
myQ.enqueue(3);
myQ.enqueue(6);
myQ.enqueue(31);
myQ.enqueue(12);

cout << myQ.getFront() << endl;
myQ.dequeue();
//cout << myQ.getFront() << endl;
cout << myQ.dequeue() << endl;

for(int i = 0; i < 5; i++)
{
for(int j = 0; j < 4; j++)
myQ.enqueue(j);

while(!myQ.isEmpty())
cout << myQ.dequeue() << endl;
}

return 0;
}