74 lines
2.0 KiB
Haskell
74 lines
2.0 KiB
Haskell
module Main (main) where
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import Control.Monad.State
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import Data.Bifunctor
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import Text.Read (readMaybe)
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main :: IO ()
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main = do
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runPuzzle puzzle1
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runPuzzle :: Puzzle a -> IO ()
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runPuzzle p = do
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Just input <- p.parse <$> readFile ("inputs/examples/" <> show p.number)
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putStrLn $ p.part1 input
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putStrLn $ p.part2 input
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data Puzzle input = Puzzle
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{ number :: Word
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, parse :: String -> Maybe input
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, part1 :: input -> String
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, part2 :: input -> String
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}
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puzzle1 :: Puzzle [(Direction, Inc)]
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puzzle1 =
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Puzzle
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{ number = 1
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, parse =
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traverse
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( \case
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'L' : (readMaybe -> Just i) -> Just (L, Inc i)
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'R' : (readMaybe -> Just i) -> Just (R, Inc i)
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_ -> Nothing
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)
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. lines
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, part1 =
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show
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. sum
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. flip evalState 50
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. traverse \(d, i) -> state \p ->
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let (_, p') = step i d p
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in (Count if p' == 0 then 1 else 0, p')
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, part2 =
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show
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. sum
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. flip evalState 50
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. traverse \(d, i) -> state \p ->
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let (c, p') = step i d p
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c' = case d of
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R -> abs c
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L ->
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if
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| p == 0 -> abs c - 1
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| p' == 0 -> abs c + 1
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| otherwise -> abs c
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in (c', p')
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}
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data Direction = L | R
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deriving (Eq, Ord, Show)
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newtype Pos = Pos Int
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deriving newtype (Eq, Ord, Show, Num)
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newtype Inc = Inc Int
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deriving newtype (Eq, Ord, Show, Num)
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newtype Count = Count Int
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deriving newtype (Eq, Ord, Show, Num)
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step :: Inc -> Direction -> Pos -> (Count, Pos)
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step (Inc i) d (Pos p) = bimap Count Pos case d of
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L -> (p - i) `divMod` 100
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R -> (p + i) `divMod` 100
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