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  1. import Data.List
  2.  
  3. main :: IO ()
  4. main = putStr
  5.      . unlines
  6.      . map show
  7.      . filter (isPandigital . toRoman)
  8.      $ [1..2000]
  9.  
  10. toRoman :: Int -> String
  11. toRoman = toRoman'
  12.   [ (1000, "M"), (900, "CM"), (500, "D"), (400, "CD")
  13.   , (100, "C"), (90, "XC"), (50, "L"), (40, "XL")
  14.   , (10, "X"), (9, "IX"), (5, "V"), (4, "IV"), (1, "I")
  15.   ]
  16.   where
  17.     toRoman' :: [(Int, String)] -> Int -> String
  18.     toRoman' _          0 = ""
  19.     toRoman' []         _ = error "Empty roman numerals"
  20.     toRoman' ((y,r):ys) x
  21.       | x < y             = toRoman' ys x
  22.       | otherwise         = r ++ toRoman' ((y,r):ys) (x - y)
  23.  
  24. isPandigital :: String -> Bool
  25. isPandigital = (== "CDILMVX") . sort
Success #stdin #stdout 0s 8388607KB
comments ()
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Standard input is empty
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https://ideone.com/N0YjkG
language:
Haskell (ghc 8.4.4)
created:
8 years ago
visibility:
public

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