import Control.Monad import Control.Applicative digit :: MonadPlus m => m Int digit = msum $ map return [0..9] exps :: Num a => [a] exps = map (10 ^) [0..] number :: Num a => [a] -> a number = sum . zipWith (*) exps . reverse uniqueDigits 0 = return [] uniqueDigits n = do xs <- uniqueDigits (n - 1) x <- digit guard $ x `notElem` xs return (x:xs) sendmoremoney = do [s,e,n,d,m,o,r,y] <- uniqueDigits 8 guard $ s /= 0 guard $ m /= 0 guard $ number [s, e, n, d] + number [m, o, r, e] == number [m, o, n, e, y] return [s, e, n, d, m, o, r, y] main = print $ (sendmoremoney :: [[Int]])
