倒排链表

题目：

Node* reverse(Node* head)
{
   if (head==NULL)
        return head;
   if(head->next==NULL) return head;
   Node* ph=reverse(head->next);
   head->next->next=head;
   head->next=NULL;
   return ph;
}


Node* reverseNonerecursive(Node* head)
{
if (head==NULL) return head;
Node* p=head;
Node* previous=NULL;
while(p->next!=NULL)  
{
    p->next=previous;
previous=p;
p=p->next;
}
p->next=previous;
return p;
}