template <class T> class mystack;
template <class T> class mystackNode {
friend class mystack<T>;
private: 
    T data;	                         //結點數據	
    mystackNode<T> *link;	       //結點鏈指針
    mystackNode ( T d = 0, mystackNode<T>*l = NULL ) : data ( d ), link ( l ) { }
};
template <class T> class mystack {
public:
    mystack ( ) : head ( NULL ) { }
    ~mystack ( );
    void push ( const T & item);
    void pop ( );
    T top ( );
    void MakeEmpty ( );         //實現與~mystack( )同
    int IsEmpty ( ) const{ return head == NULL; }
	bool IsOne(){return head!=NULL&&head->link==NULL;}
private:
    mystackNode<T> *head;       //棧頂指針
};
template <class T> mystack<T>::~mystack ( ) {
   MakeEmpty();
}

template <class T> void mystack<T>::push ( const T &item ) {
    head = new mystackNode<T> ( item, head );
    //新結點鏈入head之前, 并成為新棧頂
}
template <class T> void mystack<T>::pop ( ) {
	if( !IsEmpty ( ) ){			
    mystackNode<T> *p = head;
    T retvalue = p->data;     //暫存棧頂數據
    head = head->link;		      //修改棧頂指針
    delete p;     //釋放,返回數據
	}
}

template <class T> T mystack<T>::top( ) {
	if( !IsEmpty ( ) )
		return head->data;
	return 0;
} 	
template <class T> void mystack<T>::MakeEmpty(){
	 mystackNode<T> *p;
     while ( head != NULL )      //逐結點回收
 	 { p = head;  head = head->link;  delete p; }
}