49 lines
1.7 KiB
Haskell
49 lines
1.7 KiB
Haskell
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-- requires cabal install --lib megaparsec parser-combinators heap vector
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module Main (main) where
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import Control.Monad (void, when)
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import Data.Functor
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import qualified Data.List as L
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import qualified Data.Map as M
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import Data.Maybe
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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exampleExpectedOutput = 16
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type Input = ([String], [String]) -- patterns, designs
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type Parser = Parsec Void String
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parseInput' :: Parser Input
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parseInput' = (,) <$> some (some letterChar <* optional (string ", ")) <* eol <* eol
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<*> some (some letterChar <* eol) <* eof
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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type Memo = M.Map String Int
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compute :: Input -> Int
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compute (stripes, designs) = snd $ L.foldl' compute' (M.empty, 0) designs
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where
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compute' :: (Memo, Int) -> String -> (Memo, Int)
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compute' (memo, c) [] = (memo, c + 1)
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compute' (memo, c) design = case M.lookup design memo of
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Just c' -> (memo, c + c')
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Nothing -> let (memo', c') = L.foldl' compute' (memo, 0) $ catMaybes $ map (\s -> L.stripPrefix s design) stripes
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in (M.insert design c' memo', c + c')
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main :: IO ()
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main = do
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example <- parseInput "example"
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let exampleOutput = compute example
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when (exampleOutput /= exampleExpectedOutput) (error $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
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input <- parseInput "input"
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print $ compute input
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