反转单链表(C)

/*反转单链表*/
#include<stdio.h>
#include<stdlib.h>
#define len sizeof(struct A)
struct A {
    int num;
    struct A *next;
};
int m;
struct A *creat(int n)//创建结点个数为n的单链表
{
    struct A *head,*p1,*p2;
    m = 0;
    p1 = p2 = (struct A *)@H_421_13@malloc(len);
    scanf("%d",&p1->num);
    head = NULL;
    while (m < n)
    {
        m = m + 1;
        if (m == 1)
        {
            head = p1;
        }
        else
        {
            p2->next = p1;
        }
        p2 = p1;
        if (m < n)
        {
            p1 = (struct A*)@H_421_13@malloc(len);
            scanf("%d",&p1->num);
        }

    }
    p2->next = NULL;

    return head;
}
void print(struct A * head)//打印单链表
{
    struct A *p;
    p = head;
    if (head != NULL)
    {
        do
        {
            printf("%d ",p->num);
            p = p->next;
        } while (p != null);
    }
    
}
struct A* inverse(struct A* head)//反转单链表
{
    struct A *p1,*p2,*r;
    p2 = head;
    p1 = head->next;
    head->next = NULL;
    while (p1)
    {
        r = p1->next;
        p1->next = p2;
        p2 = p1;
        p1 = r;
    }
    head = p2;

    return head;
}
int main()
{
    printf("输入链表中结点的数目：\n");
    int n;
    scanf("%d",&n);
    printf("输入%d个结点：\n",n);
    struct A * head;
    head = creat(n);
    head=inverse(head);
    printf("输出链表中的结点：\n");
    print(head);
    
    return 0;
}