class IntervalSkipList

def find(key, path)
  cur_node = head
  (max_height - 1).downto(0) do |cur_level|
    while (next_node = cur_node.forward[cur_level]) && next_node.key < key
      cur_node = next_node
    end
    path[cur_level] = cur_node
  end
  cur_node.forward[0]
end