58 lines
1.8 KiB
Haskell
58 lines
1.8 KiB
Haskell
module Day02 where
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import Data.Maybe (fromMaybe)
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import Text.Read (readMaybe)
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data Move = Horizontal Int | Depth Int deriving Show
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data Position = Position {hPos :: Int, depth :: Int, aim::Int} deriving Show
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initialPosition :: Position
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initialPosition = Position {hPos =0, depth = 0, aim = 0}
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updatePosition :: Position -> Move -> Position
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updatePosition p@(Position {hPos = h}) (Horizontal m) = p{hPos = h + m}
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updatePosition p@(Position {depth = d}) ( Depth m) = p{depth = d + m}
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updatePosition' :: Position -> Move -> Position
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updatePosition' p@(Position {hPos=h, depth=d, aim=a}) (Horizontal m) = p{hPos=h+m, depth =d+a*m}
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updatePosition' p@(Position {hPos=h, depth=d, aim=a}) (Depth m) = p{aim=a+m}
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readDataLines:: (String -> Maybe a) -> String -> Either String [a]
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readDataLines f s = case mapM f (lines s) of
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Just xs -> Right xs
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Nothing -> Left "Error parsing string"
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finalPosition :: [Move] -> Position
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finalPosition = foldl updatePosition initialPosition
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finalPosition' :: [Move] -> Position
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finalPosition' = foldl updatePosition' initialPosition
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calcResult:: Position -> Int
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calcResult Position {hPos = h, depth =d } = h*d
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day02Part1 :: String -> String
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day02Part1 s = case readDataLines readMove s of
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Right xs -> show . calcResult . finalPosition $ xs
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Left e -> e
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day02Part2 :: String -> String
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day02Part2 s = case readDataLines readMove s of
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Right xs -> show . calcResult . finalPosition' $ xs
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readDirection ::String -> Maybe (Int -> Move)
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readDirection "forward" = Just Horizontal
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readDirection "down" = Just Depth
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readDirection "up" = Just (Depth . negate)
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readDirection _ = Nothing
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readMove :: String -> Maybe Move
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readMove s = case words s of
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[dirStr, distStr] -> readDirection dirStr <*> readMaybe distStr
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_ -> Nothing
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