Problem 8

今日は Problem 8。

　cf. Project Euler – Problem 8

module Main (main) where

import Data.List
import Data.Char

euler008 :: [Char] -> Int
euler008 n = maximum $ map euler008' $ nums n
  where
    nums = filter (\x -> length x > 4) . map (take 5) . tails
    euler008' = foldl1 (*) . map digitToInt

main :: IO ()
main = do n <- getContents >>= return . concat . lines
          putStrLn $ show $ euler008 n

^o^ >runhaskell euler008.hs < euler008.txt
40824