template<typename T>
class Stack;

// 节点定义
template<typename T>
class Node {
private:
	T info;
	Node* next;
public:
	friend class Stack<T>;
	Node() : next(nullptr) {};
	Node(T item, Node<T>* nextnode = NULL) {
		info = item;
		next = nextnode;
	}
	Node(Node<T>& node) {
		info = node.info;
		next = node.next;
	}
};

// 栈定义
template<typename T>
class Stack {
private:
	Node<T>* top;
public:
	Stack() {
		top = NULL;
	}
	bool push(const T& item) {
		Node<T>* p = top;
		top = new Node<T>;
		top->info = item;
		top->next = p;
		return true;
	}
	bool pop() {
		if (top == NULL) return false;
		else {
			Node<T>* p = top;
			top = top->next;
			delete p;
		}
		return true;
	}
	T peek() {
		return top->info;
	}
	~Stack() {
		Node<T>* p = top;
		while (top) {
			top = top->next;
			delete p;
			p = top;
		}
		top = p = NULL;
	}
	bool empty() {
		return top == NULL;
	}
};