type ntree = Leaf of string | Ntr of string * ntree list;;
let ntr1 = Ntr("/", [Ntr("etc", [Leaf("fstab");Leaf("mtab")]);Leaf(".empty")]);;
let find_path ntr l1 =
    let rec fp' ctl lc =
      match lc with
          [] -> true
      | x::xs ->
        match ctl with
          Ntr(path, nls)::ys ->
            if (x = path) then
                fp' nls xs (* go down the tree then! *)
            else
                fp' ys lc (* try to match at the same tree level *)
        |  Leaf(path)::ys ->
            if (x = path) then
                fp' ys xs (* go down the path *)
            else
                fp' ys lc (* search at the same level *)
        | _ -> false
    in
    fp' [ntr] l1;;