程序代码：

#include <stdio.h>
#include <malloc.h>
struct stack{
    int elem;
    struct stack *top;
}stacka;
struct stack *init(struct stack *s){
    s=(struct stack *)malloc(sizeof(struct stack));
    s->top=NULL;
    return s;
}
void push(struct stack *s,int n){
    struct stack *p;
    p=(struct stack *)malloc(sizeof(struct stack));
    p->elem=n;
    p->top=s->top;
    s->top=p;
}
int pop(struct stack *s){
    int e;
    struct stack *p;
    if(s->top!=NULL){
        e=s->top->elem;
        p=s->top;
        s->top=p->top;
        free(p);
        return e;
    }else
        printf("栈空");
}
void main(){
    int i;
    struct stack *stack;
    stack=init(stack);
    for(i=0;i<3;i++)
        push(stack,i);
    for(i=0;i<7;i++)
        printf("%3d",pop(stack));
}
如果只想出现4 3 2 1 0 空栈  怎么办呢？