单链表的就地逆置

#include <stdio.h>
#include <assert.h>
#include <malloc.h>

typedef struct NODE
{
    int data;

    struct NODE *next;
}Linklist;

void Reverse(Linklist *head)
{
    assert (NULL != head);

    Linklist *p1 = NULL;
    Linklist *p2 = NULL;

    if ((NULL == (head->next)) || (NULL == (head->next->next)))
    {
        return;
    }

    p1 = head->next;
    p2 = p1->next;

    while (NULL != p2)
    {
        p1->next = p2->next;
        p2->next = head->next;
        head->next = p2;
        p2 = p1->next;
    }
}

void initialLinklist(Linklist **head)
{
    assert (head != NULL);

    if (NULL == (*head = (Linklist *)malloc(sizeof(Linklist))))
    {
        printf ("Fail to malloc space to *head!\n");
        return;
    }

    (*head)->next = NULL;
}

void CreatLinklist(Linklist *head)
{
    assert (head != NULL);

    int data;
    Linklist *p = head;

    printf ("Please input NODE number, end with -1:\n");
    scanf ("%d", &data);
    while (data != -1)
    {
        if (NULL == ((p->next) = (Linklist *)malloc(sizeof(Linklist))))
        {
            printf ("Fail to malloc space to head->next!\n");
            return;
        }

        p = p->next;
        p->data = data;
        p->next = NULL;

        scanf ("%d", &data);
    }
}

void PrintLinklist(Linklist *head)
{
    assert (head != NULL);

    Linklist *p = head->next;

    while (p != NULL)
    {
        printf ("%d ", p->data);

        p = p->next;
    }

    printf ("\n");
}

void FreeLinklist(Linklist *head)
{
    assert (head != NULL);

    Linklist *p = head->next;

    while (p != NULL)
    {
        head->next = p->next;

        free (p);
        
        p = head->next;
    }

    free (head);
    head = NULL;
}

int main(void)
{
    Linklist *head = NULL;

    initialLinklist (&head);

    CreatLinklist (head);

    Reverse (head);

    PrintLinklist (head);

    FreeLinklist (head);

    return (0);
}