#include <iostream>
#include <cassert>

using namespace std;

class Stack
{
public:
	Stack();
	~Stack();
	int top() const;
	void push(const int v);
	void pop();
	bool isEmpty() const;
private:
	struct Node;
	struct Node
	{
		Node* pNext_;
		int data_;
	};
	Node* pHead_ = nullptr;
};
int main()
{
	Stack a;

	cout << a.isEmpty() << endl;
	a.push(3);
	cout << a.isEmpty() << endl;
	a.pop();
	cout << a.isEmpty() << endl;
	a.push(3);
	a.push(3);
};

Stack::Stack() = default;

Stack::~Stack()
{
	while (!isEmpty())
	{
		pop();
	}
}
void
Stack::push(const int v)
{
	Node* pNew = new Node;
	pNew->pNext_ = pHead_;
	pNew->data_ = v;
	pHead_ = pNew;
}
bool
Stack::isEmpty() const
{
	return (nullptr == pHead_);
}
void
Stack::pop()
{
	if (!isEmpty())
	{
		Node* pDeleted{ pHead_ };
		pHead_ = pDeleted->pNext_;
		delete pDeleted;
	}
}