学步园

#include <iostream>
using namespace std;

template<typename T> class myStack;

template<typename T>
class node
{
	friend class myStack<T>;
	T data;
	node *next, *parent;	
};

template<typename T>
class myStack
{
public:
	myStack();
	~myStack();
	void push(const T&);
	T& top();
	void pop();
	bool empty();
	int size()
	{
		return length;
	}
private:
	void destroy();
	node<T> *bottom, *head;	
	int length;
};

template<typename T>
myStack<T>::myStack() : bottom(0), head(0), length(0){
	
}

template<typename T>
myStack<T>::~myStack()
{
	destroy();
}

template<typename T>
void myStack<T>::push(const T& val)
{
	node<T> *t = new node<T>;
	t->data = val;
	t->next = 0;
	
	if(empty())
	{
		head = bottom = t;
		head ->parent = 0;
	}
	else
	{
		head->next = t;
		t->parent = head;
		head = t;
	}		
	length++;	
}

template<typename T>
T& myStack<T>::top()
{
	return head->data;
}

template<typename T>
void myStack<T>::pop()
{
	node<T> *p = head;
	head = head->parent;
	delete p;
	length--;
}

template<typename T>
bool myStack<T>:: empty()
{
	return head == 0;	
}

template<typename T>
void myStack<T>::destroy()
{
	while(!empty())
		pop();
}

int main(void)
{
	myStack<int> st;
	for(int i = 1; i <= 10; ++i)
	{
		st.push(i);
	}	
	cout << "size: " << st.size() << endl;
	for(int j = 0; j < 10; ++j)
	{
		if(!st.empty())
		{
			cout << st.top() << endl;
			st.pop();
			cout << "size: " << st.size() << endl;
		}
	}
	
	return 0;
}