#include<stdio.h>
#include<stdlib.h>

typedef struct NODE
{
    char data;
    struct NODE *next;
}NODE;

NODE *push_stack(NODE *head);
void free_space(NODE *p);


int main()
{
    NODE *head = NULL,*p = NULL;//链表都要有头结点 和头指针

    p = push_stack(head);

    while(p)
    {
        putchar(p->data);
        p = p->next;
    }

    putchar(10);

    free_space(p);

    return 0;
}

NODE *push_stack(NODE *head)
{
    char string;
    NODE *stack = NULL;

    while(1)
    {
        string = getchar();
        if(string == '\0')
            break;
        stack = (NODE *)malloc(sizeof(struct NODE));//倒叙插入法  栈特性
        stack->data = string;
        stack->next = head;
        head = stack;
    }
    return head;
}

void free_space(NODE *p)//直接递归释放就可以了
{
    if(p->next)
        free_space(p->next);
    free(p);
}