static Node nodeReverse(Node head)
{
    if (head == null || head.next == null) return head;
    Node new_head = null;

    while (head != null)
    {
        Node temp = head;
        head = head.next;
        temp.next = new_head;
        new_head = temp;
    }

    return new_head;
}

static Node nodeReverse(Node head)
{
    if (head == null || head.next == null) return head;
    Node begin = head;
    Node end = head.next;

    while (end != null)
    {
        begin.next = end.next;
        end.next = head;
        head = end;
        end = begin.next;
    }

    return head;
}