单链表的逆序

typedef struct node
{
        int data;
        struct node *next;
}Node;

Node *reverseNode(Node *head)
{
        Node *p, *q, *r;
        if(head==NULL || head->next==NULL)
                return head;
        p=head->next;
        q=p->next;
        r=q->next;
        p->next=NULL;
        while(r != NULL)
        {
                q->next=p;
                p=q;
                q=r;
                r=r->next;
        }

        q->next=p;
        head->next=q;

        return head;
}