实现一个函数，将给定的单链表逆转。

List Reverse(List L)
{
	List head, tail, mid;
	tail = NULL;
	mid = L;

	while (mid != NULL)
	{
		head = mid->Next;
		mid->Next = tail;
		tail = mid;
		mid = head;
		
	}

	return tail;
}