c++ 模板 栈实现

#include <iostream>

using namespace std;

template <class Node>
class StackNode
{
    public:
        StackNode();
        ~StackNode();
        Node node;
        StackNode *next;
};

template<class Node>
StackNode<Node>::StackNode()
{

}

template<class Node>
StackNode<Node>::~StackNode()
{
    cout<<"destory"<<endl;
}

template<class T>
class Stack
{
    public:
        Stack();
        Stack(const Stack& stack); //  拷贝构造函数 
        ~Stack();
        void push(const T& item); //入栈
        StackNode<T> *popup();   //出栈
        bool isEmpty();  //判空
        int getLength();  //获取栈长度
        void clean();    //清空


        StackNode<T> *head;

        void printStack();  //打印栈数据
        int length ;
};

template<class T>
Stack<T>::Stack()
{
    head = NULL;
    length = 0;
}

template<class T>
Stack<T>::~Stack()
{    

}

template<class T>
Stack<T>::Stack(const Stack& stack)
{
    head = NULL;
    length = 0;

    StackNode< T> *tmp = stack.head;

    while(tmp !=NULL)
    {

        StackNode<T> *stackNode = new StackNode<T>();
        stackNode->node  = tmp->node;
        stackNode->next = head;
        head = stackNode;

        length+=1;

        tmp = tmp->next;

    }
}


template<class T>
void Stack<T>::push(const T& item)
{
    StackNode<T> *stackNode = new StackNode<T>();
    stackNode->node = item;
    stackNode->next = head;

    head  =stackNode;

    length+=1;

}

template<class T>
StackNode<T> *Stack<T>::popup()
{

    if(head !=NULL)
    {
        StackNode<T> *tmp = head;

        head = head->next;

        length -=1;

        return tmp;
    }
    else
    {
        return NULL;
    }
}

template<class T>
bool Stack<T>::isEmpty()
{
    if(head == NULL)
    {
        return true;
    }
    else
    {
        return false;
    }
}

template <class T>
int Stack<T>::getLength()
{
    if(length<0)
    {
        length = 0;
        return 0;
    }
    else
    {
        return length;
    }
}

template<class T>
void Stack<T>::clean()
{
    if(head !=NULL)
    {
        StackNode<T> *tmp = head;
        StackNode<T> *current;

        while(tmp !=NULL)
        {
            current = tmp;
            tmp = tmp->next;

            delete current;
        }
    }
}

template<class T>
void Stack<T>::printStack()
{
    StackNode<T> *tmp = head;

    if(tmp !=NULL)
    {
        while(tmp !=NULL)
        {
            cout<<tmp->node<<endl;

            tmp = tmp->next;
        }
    }
}

int main()
{

    Stack<int > *stack = new Stack<int>();

    for(int i=0;i<10;i++)
    {
        stack->push(i);
    }

    stack->printStack();

    StackNode<int> *tmp = stack->popup();

    if(tmp !=NULL)
    {
        cout<<tmp->node<<endl;
        delete tmp;
        tmp = NULL;

    }
    else
    {
        cout<<"123"<<endl;
        tmp = NULL;
    }

    tmp = stack->popup();

    if(tmp !=NULL)
    {
        cout<<tmp->node<<endl;
        delete tmp;
        tmp = NULL;
    }
    else
    {
        cout<<"123"<<endl;
        tmp = NULL;
    }

    if(stack->isEmpty())
    {
        cout<<"empty "<<endl;
    }
    else
    {
        cout<<"NoEmpty "<<endl; 
    }

    cout<<stack->getLength()<<endl;

    cout<<"*************************************"<<endl;

    Stack<int>& a = *stack;
    Stack<int> *stack1 = new Stack<int>(a);

    cout<<stack1->getLength()<<endl;

    stack1->printStack();

    stack->clean();
    stack1->clean();

}