Solution to the Google Code Jam Qualification Round Problem #1

foregone-solution.hs

import Control.Monad

getA :: [Char] -> [Char]
getA n = map (\x -> if x == '4' then '2' else '0') n

getB :: [Char] -> [Char]
getB n = map (\x -> if x == '4' then '2' else x) n

solveCase :: [Char] -> (String, String)
solveCase n = (getA n, getB n)

caseSolutionString :: (Int, [Char]) -> String
caseSolutionString (i, n) = "Case #" ++ show i ++ ": " ++ fst sol ++ " " ++ snd sol
    where sol = solveCase n

readCase :: Int -> IO (Int, String)
readCase i = do 
    nstr <- getLine
    return (i, takeWhile (\c -> (c /= '\r') && (c /= '\n')) nstr)

main = do
    t <- getLine
    let tn = (read t) :: Int
    cases <- forM [1..tn] readCase
    mapM putStrLn (map caseSolutionString cases)