#include <iostream>

// 节点结构
template <typename T>
struct Node {
    T data;
    Node* next;
    Node(const T& data) : data(data), next(nullptr) {}
};

// 链栈类模板
template <typename T>
class LinkStack {
private:
    Node<T>* top;  // 栈顶指针
    size_t size;   // 栈大小

public:
    // 构造函数
    LinkStack() : top(nullptr), size(0) {}

    // 析构函数
    ~LinkStack() {
        while (!isEmpty()) {
            pop();
        }
    }

    // 判断栈是否为空
    bool isEmpty() const {
        return top == nullptr;
    }

    // 获取栈的大小
    size_t getSize() const {
        return size;
    }

    // 入栈操作
    void push(const T& data) {
        Node<T>* newNode = new Node<T>(data);
        newNode->next = top;
        top = newNode;
        ++size;
    }

    // 出栈操作
    void pop() {
        if (isEmpty()) {
            std::cout << "Stack is empty, cannot pop.\n";
            return;
        }
        Node<T>* temp = top;
        top = top->next;
        delete temp;
        --size;
    }

    // 获取栈顶元素
    T peek() const {
        if (isEmpty()) {
            throw std::runtime_error("Stack is empty, cannot peek.");
        }
        return top->data;
    }
};

int main() {
    LinkStack<int> stack;

    // 测试入栈操作
    stack.push(10);
    stack.push(20);
    stack.push(30);

    // 打印栈顶元素
    std::cout << "Top element: " << stack.peek() << std::endl;

    // 测试出栈操作
    stack.pop();
    std::cout << "Top element after pop: " << stack.peek() << std::endl;

    // 测试栈大小
    std::cout << "Stack size: " << stack.getSize() << std::endl;

    // 清空栈
    while (!stack.isEmpty()) {
        std::cout << "Popping: " << stack.peek() << std::endl;
        stack.pop();
    }

    return 0;
}