单链表反向

struct node* fanxiang(struct node* head)
{
struct node *p1 = head ;
struct node *p2 = p1->next ;
struct node *p3 = p2->next ;
if ( head == NULL || head->next == NULL )
return head;
p1->next = NULL ;
while ( p3->next != NULL )
{
p2->next = p1 ;
p1 = p2 ;
p2 = p3 ;
p3 = p3->next ;
}
p2->next = p1 ;
head = p2 ;
return head ;

}