Merge arrays #2

array.hs

{-# LANGUAGE OverloadedStrings #-}
import Control.Monad
import Data.Array.IO
import Data.Array.Base
import Data.Char (ord)
import Data.Word
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as C8
import qualified Data.ByteString.Builder as Builder
import System.IO

type Number = Word8
type Count = Int -- сколько там может быть чисел на входе?...
type DataArray = IOUArray Number Count

addToIOArray :: DataArray -> Int -> IO ()
addToIOArray arr idx = do
  val <- unsafeRead arr idx
  unsafeWrite arr idx $ val + 1

fillIOArray :: DataArray -> IO ()
fillIOArray arr = readLine >>= addList
  where
    readLine = parseLine <$> B.getLine
    parseLine = tail . map parseInt . B.split (fromIntegral $ ord ' ')
    parseInt str = case C8.readInt str of
                     Nothing -> error $ "not an integer: " ++ show str
                     Just (int, _) -> int
    addList = mapM_ (addToIOArray arr)

printPair :: (Number, Count) -> IO ()
printPair (x, n) = replicateM_ (fromIntegral n) $ do
    Builder.hPutBuilder stdout $ Builder.word8Dec x <> Builder.byteString "\n"

main :: IO ()
main = do
    k <- read <$> getLine
    arr <- newArray (0,100) 0 :: IO DataArray
    replicateM k $ fillIOArray arr
    hSetBuffering stdout (BlockBuffering Nothing)
    getAssocs arr >>= mapM_ printPair