diff options
Diffstat (limited to '')
-rw-r--r-- | 2023/15-Lens_Library/second.hs | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/2023/15-Lens_Library/second.hs b/2023/15-Lens_Library/second.hs new file mode 100644 index 0000000..c7b3f53 --- /dev/null +++ b/2023/15-Lens_Library/second.hs @@ -0,0 +1,89 @@ +-- requires cabal install --lib megaparsec parser-combinators +module Main (main) where + +import Control.Applicative.Permutations +import Control.Monad (void, when) +import Data.Char qualified as C +import Data.Either +import Data.Functor +import Data.List qualified as L +import Data.Map qualified as M +import Data.Maybe +import Data.Set qualified as S +import Data.Vector qualified as V +import Data.Void (Void) +import Text.Megaparsec +import Text.Megaparsec.Char + +import Debug.Trace + +exampleExpectedOutput = 145 + +data Op = Equal Int | Minus deriving (Eq, Show) +data Step = Step String Op deriving (Eq, Show) +type Input = [Step] + +type Parser = Parsec Void String + +parseNumber :: Parser Int +parseNumber = read <$> some digitChar <* optional (char ',') + +parseOp :: Parser Op +parseOp = char '-' $> Minus + <|> char '=' *> (Equal <$> parseNumber) + +parseStep :: Parser Step +parseStep = Step <$> some letterChar + <*> parseOp <* optional (char ',') + +parseInput' :: Parser Input +parseInput' = some parseStep <* 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' + +data Lens = Lens String Int deriving (Eq, Show) +type Box = [Lens] + +compute :: Input -> Int +compute input = sum $ zipWith (curry score) [1..] $ L.foldl' step initialBoxes input + where + score :: (Int, Box) -> Int + score (i, lenses) = sum $ zipWith (curry $ scoreLens i) [1 .. ] lenses + scoreLens :: Int -> (Int, Lens) -> Int + scoreLens i (j, Lens _ k) = i * j * k + initialBoxes = replicate 256 [] + step :: [Box] -> Step -> [Box] + step boxes (Step label Minus) = take i boxes + ++ remove [] (boxes L.!! i) + : drop (i+1) boxes + where + i = hash 0 label + remove :: Box -> Box -> Box + remove out [] = out + remove out (l@(Lens ll _):ls) | ll == label = remove out ls + | otherwise = remove (out ++ [l]) ls + step boxes (Step label (Equal f)) = take i boxes + ++ process [] (boxes L.!! i) + : drop (i+1) boxes + where + i = hash 0 label + process :: Box -> Box -> Box + process out [] = out ++ [Lens label f] + process out (l@(Lens ll _):ls) | ll == label = out ++ Lens label f : ls + | otherwise = process (out ++ [l]) ls + hash :: Int -> String -> Int + hash i [] = i + hash i (x:xs) = hash (((i + C.ord x) * 17) `rem` 256) xs + +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 |