#include <iostream>

using namespace std;

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

Node *init()    
{
    Node *dummy = new Node(-1);
    return dummy;
}

bool empty(Node *dummy){
    return dummy -> next == NULL;//链式存储只可能空，一般不可能满
}

void push(Node *dummy,int val){ //头插法
    Node *node = new Node(val);
    node -> next = dummy -> next;
    dummy -> next = node;
}

void pop(Node *dummy){
    Node *node = dummy -> next;
    dummy -> next = node -> next;
    delete node;
}

int top(Node *dummy){
    return dummy -> next -> val;
}

void print(Node *dummy){
    Node *p = dummy -> next;
    while(p != NULL){
        cout << p -> val << ' ';
        p = p -> next;
    }
}

int main()  
{
    // 测试链栈各操作
    Node *dummy = init();
    push(dummy, 1);
    push(dummy, 2);
    push(dummy, 3);
    push(dummy, 4);

    printf("栈顶元素：%d\n", top(dummy));

    pop(dummy);

    printf("栈顶元素：%d\n", top(dummy));

    printf("栈是否为空：%d\n", empty(dummy));

    print(dummy);

    return 0;
}