Google Code Jam Round 1A 2014 problem C: Proper Shuffle. Testing on my machine correctly identified 88.6% of 1000 good shuffles and 98.1% of 1000 bad shuffles. I don't know why...

gistfile1.hs

-- @betaveros
-- Google Code Jam Round 1A 2014: Proper Shuffle (polished version)
import Control.Applicative
import Control.Monad
import Text.Printf

inputInt :: IO Int
inputInt = read <$> getLine
inputInts :: IO [Int]
inputInts = map read . words <$> getLine

countAgainstIndex :: (Int -> Int -> Bool) -> [Int] -> Int
countAgainstIndex vs = length . filter id . zipWith vs [0..]

guessBad :: [Int] -> Bool
guessBad ls = countAgainstIndex (>) ls < countAgainstIndex (<) ls - 20

tc :: Int -> IO ()
tc tci = do
    _ <- inputInt
    perm <- inputInts
    printf "Case #%d: %s\n" tci $ if guessBad perm then "BAD" else "GOOD"

main :: IO ()
main = do
    tcn <- inputInt
    forM_ [1..tcn] tc