Solutions for https://code.google.com/codejam/contest/351101/dashboard#s=p0

solution.hs

import Data.Maybe
import Prelude hiding (drop, head, tail, (++), mapM_, zip, length, null)
import Data.Vector
import qualified Data.List as L
import System.Environment
import Control.Applicative

calculate :: (Int, Int, Vector Int) -> (Int, Int)
calculate (c, _, vec) = aux 0
    where aux i = let p = vec ! i in
                  let ps = drop (i+1) vec in
                  let index = findIndex (\x -> x+p==c) ps in
                  if isJust index then (i+1, 2+i+fromJust index)
                  else aux (i+1)
                         

parse :: Vector String -> Vector (Int, Int, Vector Int)
parse vec
    | null vec = Data.Vector.empty
    | otherwise = let c = vec ! 0 in
            let i = vec ! 1 in
            let ps = vec ! 2 in
            let end = drop 3 vec in
            singleton (read c, read i, read <$> fromList (words ps)) ++ parse end

main :: IO ()
main = do
  fileName <- L.head <$> getArgs
  contents <- fromList <$> lines <$> readFile fileName
  let result = calculate <$> parse (tail contents)
  mapM_ (\(i, (x, y)) ->
             putStrLn $ "Case #" L.++ show (i+1) L.++ ": " L.++ show x L.++ " " L.++ show y) $
      imap (,) result
  return ()

solution.ml

module Option =
  struct
    let is_some = function
      | Some _ -> true
      | None -> false

    let from_some = function
      | Some a -> a
      | None -> raise Not_found
  end

open Array

let last arr = get arr (length arr - 1)

let drop i arr = sub arr i (length arr - i)

let find_index f arr =
  let index = ref None in
  iteri (fun i a -> if f a then index := Some i) arr;
  !index

let calculate c i vec =
  let rec aux i =
    let p = get vec i in
    let ps = drop (i+1) vec in
    let index = find_index (fun x -> x+p=c) ps in
    if Option.is_some index then (i+1, 2+i+Option.from_some index)
    else aux (i+1) in
  aux 0

let () =
  let file_name = last Sys.argv in
  let file = open_in file_name in
  try
    let _ = input_line file |> int_of_string in
    let case = ref 0 in
    while true do
      let c = input_line file |> int_of_string in
      let i = input_line file |> int_of_string in
      let ps = input_line file |> Str.split (Str.regexp " ") |> Array.of_list |> map int_of_string in
      let (x, y) = calculate c i ps in
      case := !case+1;
      Printf.printf "Case %d: %d %d\n" !case x y
    done
  with End_of_file ->
    close_in file