ch3

int (int *a,int top,int elem){
  a[++top]=elem;
   return top;
}

//数据元素出栈
int pop(int *a,int top){
 if(top==-1){
        printf("空栈");
      return -1; 
 }
    printf("弹栈元素：%dn",a[top]);
 top--;
   return top;
}

int main() {
    int a[100];
    int top=-1;
    top=push(a, top, 1);
    top=push(a, top, 2);
    top=push(a, top, 3);
    top=push(a, top, 4);
    top=pop(a, top);
    top=pop(a, top);
    top=pop(a, top);
    top=pop(a, top);
    top=pop(a, top);
    return 0;
}