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import Control.Monad.ST
import Data.HashTable.ST.Basic as H
import Data.List (nub)
import Data.Maybe (mapMaybe)
type S s = H.HashTable s String [String]
-- Return Nothing if no match; unmatched remainder (can be []) if
-- match.
match :: String -> String -> Maybe String
match xs [] = Just xs
match (x:xs) (y:ys) | x == y = match xs ys
| otherwise = Nothing
match [] _ = Nothing
matchAny :: S s -> [String] -> String -> ST s [String]
matchAny s yss xs = do
t <- H.lookup s xs
case t of
Nothing -> let r = mapMaybe (match xs) yss
in H.insert s xs r >> return r
Just x -> return x
check :: S s -> [String] -> [String] -> ST s Bool
check s yss xss = do
zss <- nub . concat <$> mapM (matchAny s yss) xss
if null zss
then return False
else if [] `elem` zss
then return True
else check s yss zss
parseTowels :: String -> [String]
parseTowels = map init . words
parse :: String -> ([String],[String])
parse s = let yss = filter (not . null) . drop 2 $ lines s
xss = parseTowels . head $ lines s
in (xss, yss)
run :: [String] -> [String] -> ST s Int
run xss yss = do
ht <- H.new :: ST s (S s)
length . filter id <$> traverse (check ht yss . pure) xss
main :: IO ()
main = do
input <- getContents
let (xss, yss) = parse input
print $ runST $ run yss xss
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