单链表实现队列

//单链表实现队列
#include<new>
#include<iostream>

template <typename T> struct Node{
    T data;
    Node * next;
}; 

template <typename T> class Queue
{
    public:
        typedef Node<T> * PtrToQueue;
    private:
        PtrToQueue first;
        PtrToQueue last;
    public:
        bool IsEmpty()
        {
            return first->next == NULL;
        }
        void MakeEmpty()
        {
            if( !IsEmpty() )
                while( !IsEmpty() )
                    Dequeue();
        }
        void Enqueue( T x )
        {
            PtrToQueue tmp;
            tmp = new Node<T>;
            tmp->data = x;
            tmp->next = NULL;
            last->next = tmp;
            last = tmp;
        }
        T Front()
        {
            return first->next->data;
        }
        void Dequeue()
        {
            PtrToQueue tmp;
            tmp = first;
            first = first->next;
            delete tmp; 
        }
        T FrontAndDequeue()
        {
            T d = Front();
            Dequeue();
            return d;
        }
        int length()
        {
            int i;
            Node<T> * p = first;
            for(i=0;p!=last;i++,p=p->next);
            return i;
        }
        Queue(  )
        {
            first = new Node<T>;
            first->data = 0;
            first->next = NULL;
            last = first;
        }
        ~Queue()
        {
            MakeEmpty();
            delete first;
        }
};