#include <iostream>

using namespace std;

const int N = 100010;

struct Node {
    int  val;
    Node *next;
    Node (): next(NULL){}
    Node(int _val): val(_val), next(NULL){}
};

void print(Node *top)
{
    for(auto p = top->next; p; p = p->next)
    {
        cout << p->val << " ";
    }cout << endl;
}

int main()
{
    Node *top = new Node();

    auto a = new Node(1);

    a->next = top->next;
    top->next = a;
    print(top); 
    cout << "栈顶是" << top->next->val << endl;

    auto b = new Node(2);
    b->next = top->next;
    top->next = b;
    print(top);
    cout << "栈顶是"<< top->next->val << endl;

    top->next = top->next->next;
    delete b;

    print(top);
    cout << "栈顶是" << top->next->val << endl;

    top->next = top->next->next;
    delete a;

    if(top->next == NULL)
        cout << "栈为空" << endl;
    else 
        cout << "栈不为空" << endl;



    return 0;
}