#include<stdio.h>
//定义栈的结构
struct stacktype

{

   int stack[4];//存放数据元素
   int top;//栈顶指针
};

struct stacktype * InitialStack()

{

 struct stacktype * head;

 head=(struct stacktype *)

    malloc(sizeof(struct stacktype ));

 head->top=-1;// <=> s.top=-1
 return head;

}
//入栈
void PushIntoStack(struct stacktype * head,

                   int value)

{

 if(head->top==3)

    printf("Push Failed \n");

 else

    {

     head->top++;//
     head->stack[head->top]=value;

     }

}
void output(struct stacktype * head)

{

   int i;

   for(i=0;i<=head->top;i++)

       printf(" %d ",head->stack[i]);

}

void main()

{  

  struct stacktype * head;

  head=InitialStack();

  PushIntoStack(head,1);

  PushIntoStack(head,2);

  PushIntoStack(head,3);

  output(head);

}