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