#include<stdio.h>

#include<stdlib.h>

//用链表实现栈

typedef struct Node {

    int data;

    struct Node *next;

} node;

int IsEmpty(node *p) {

    return p->next==NULL;

}

node *CreateStack() {

    node *p=(node*)malloc(sizeof(node));

    p->next=NULL;

    return p;

}

node *Push(node *p,int x) {

    node *TmpCell=(node*)malloc(sizeof(node));

    TmpCell->data=x;

    TmpCell->next=p->next;

    p->next=TmpCell;

    return p;

}

void Pop(node *p) {

    node *cell;

    if(p->next==NULL) {

        printf("error,-1");

    } else {

        cell=p->next;

        p->next=cell->next;

        free(cell);

    }

}

void display(node *p) {

    node *temp=p;

    while(temp->next) {

        printf("%d",temp->next->data);

        temp=temp->next;

    }

    printf("%c",'\n');

}

main() {

    node *p=CreateStack();

    Push(p,);

    Push(p,);

    Push(p,);

    Push(p,);

    display(p);

    Pop(p);

    display(p);

    Pop(p);

    display(p);

}