2019-09-12 10:33:56 -07:00
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import Data.List (mapAccumL, isPrefixOf)
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import Control.Arrow ((***))
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2017-09-23 10:01:46 +02:00
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2019-09-12 10:33:56 -07:00
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romanValue :: String -> Int
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romanValue =
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let tr s (k, v) =
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until (not . isPrefixOf k . fst) (drop (length k) *** (v +)) (s, 0)
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in sum .
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snd .
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flip
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(mapAccumL tr)
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[ ("M", 1000)
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, ("CM", 900)
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, ("D", 500)
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, ("CD", 400)
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, ("C", 100)
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, ("XC", 90)
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, ("L", 50)
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, ("XL", 40)
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, ("X", 10)
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, ("IX", 9)
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, ("V", 5)
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, ("IV", 4)
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, ("I", 1)
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]
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2017-09-23 10:01:46 +02:00
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main :: IO ()
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2019-09-12 10:33:56 -07:00
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main =
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mapM_ (print . romanValue) ["MDCLXVI", "MCMXC", "MMVIII", "MMXVI", "MMXVII"]
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