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oskimura/Euler20.hs

Created October 1, 2010 11:24
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Euler20.hs
module Euler20 where
import Data.Maybe (fromMaybe)
-- 文字(0-9)を数字に
charToInteger :: Char -> Maybe Integer
charToInteger = flip lookup (zip ['0'..'9'] [0..9])
-- 文字列(0-9)*を数字に
strToInt :: String -> [Integer]
strToInt = map (fromMaybe 0 . charToInteger)
euler20 = sum . toDidits $ 100
where
toDidits = strToInt . text
text = show . fact
fact n = product [1..n]
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