ACM International Collegiate Programming Contest, Asia Regional (Tokyo), 2004, Problem C

gistfile1.ml

open List;;
open Int64;;

let binary_list_of_int n =
  let rec binary_list_of_int n bit =
    if bit = 1 then [n]
    else (rem n (of_int 2)) :: binary_list_of_int (div n (of_int 2)) (bit-1)
  in
    binary_list_of_int n 32;;

let get_key l =
  let n9 = binary_list_of_int (hd (rev l)) in
  let binl = map binary_list_of_int (tl (rev l)) in
  let one_nums l = fold_right add (map hd l) zero
  in
  let rec get_key_1 binl n n9 = 
    match n9 with
        [] -> []
      | x :: xs -> 
          let m = one_nums binl in
          let binl_xs = map tl binl in
          if rem (add m n) (of_int 2) = x
          then
            zero :: get_key_1 binl_xs (div (add m n) (of_int 2)) xs
          else
            one :: get_key_1 binl_xs
              (div (add (sub (of_int 8) m) n) (of_int 2)) xs
  in
    of_string ("0b" ^ 
                 (fold_right (^)
                    (rev (map to_string (get_key_1 binl zero n9))) ""));;

let get_text filename =
  let input = open_in filename in
  let s = ref (int_of_string (input_line input)) in
    try
      while !s > 0 do
        let rec get_next_n_list input l =
          match length l with
              9 -> l
            | n ->
                get_next_n_list input
                  (append l 
                     (Str.split (Str.regexp_string " ") (input_line input)))
        in
          Printf.printf "%Lx\n"
                         (get_key
                            (map
                               (fun s -> of_string ("0x" ^ s))
                               (get_next_n_list input [])));
          s := !s - 1;
      done
    with
        End_of_file -> ();;

Arg.parse [] (fun s -> get_text (s)) ("");;