48 lines
1.4 KiB
Haskell
48 lines
1.4 KiB
Haskell
import Data.List.Split ( chunksOf )
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import Data.List ( (!!) )
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isPrime :: Int -> Bool
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isPrime n
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|n == 2 = True
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|n == 1 = False
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|otherwise = null $ filter (\i -> mod n i == 0 ) [2 .. root]
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where
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root :: Int
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root = floor $ sqrt $ fromIntegral n
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isMagnanimous :: Int -> Bool
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isMagnanimous n = all isPrime $ map (\p -> fst p + snd p ) numberPairs
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where
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str:: String
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str = show n
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splitStrings :: [(String , String)]
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splitStrings = map (\i -> splitAt i str) [1 .. length str - 1]
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numberPairs :: [(Int , Int)]
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numberPairs = map (\p -> ( read $ fst p , read $ snd p )) splitStrings
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printInWidth :: Int -> Int -> String
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printInWidth number width = replicate ( width - l ) ' ' ++ str
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where
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str :: String
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str = show number
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l :: Int
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l = length str
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solution :: [Int]
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solution = take 400 $ filter isMagnanimous [0 , 1 ..]
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main :: IO ( )
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main = do
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let numbers = solution
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numberlines = chunksOf 10 $ take 45 numbers
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putStrLn "First 45 magnanimous numbers:"
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mapM_ (\li -> putStrLn (foldl1 ( ++ ) $ map (\n -> printInWidth n 6 )
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li )) numberlines
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putStrLn "241'st to 250th magnanimous numbers:"
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putStr $ show ( numbers !! 240 )
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putStrLn ( foldl1 ( ++ ) $ map(\n -> printInWidth n 8 ) $ take 9 $
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drop 241 numbers )
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putStrLn "391'st to 400th magnanimous numbers:"
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putStr $ show ( numbers !! 390 )
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putStrLn ( foldl1 ( ++ ) $ map(\n -> printInWidth n 8 ) $ drop 391 numbers)
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