template <class T>
List<T> List<T>::split(int splitPoint)
{
    if (splitPoint > length)
        return List<T>();

    if (splitPoint < 0)
        splitPoint = 0;

    ListNode * secondHead = split(head, splitPoint);

    int oldLength = length;
    if (secondHead == head)
    {
        // current list is going to be empty
        head = NULL;
        tail = NULL;
        length = 0;
    }
    else
    {
        // set up current list
        tail = head;
        while (tail->next != NULL)
            tail = tail->next;
        length = splitPoint;
    }

    // set up the returned list
    List<T> ret;
    ret.head = secondHead;
    ret.tail = secondHead;
    if (ret.tail != NULL)
    {
        while (ret.tail->next != NULL)
            ret.tail = ret.tail->next;
    }
    ret.length = oldLength - splitPoint;
    return ret;

}