32 lines
977 B
Haskell
32 lines
977 B
Haskell
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import qualified Data.HashMap.Strict as HMS
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import Data.List (foldl1')
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type DataMap = HMS.HashMap String (String, String)
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getDirection :: Char -> (a, a) -> a
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getDirection 'L' = fst
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getDirection 'R' = snd
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countTimes :: String -> DataMap -> String -> Int
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countTimes directions m start = countTimes' directions start 0
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where
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countTimes' (d:ds) ss@(s:_)
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| s == 'Z' = id
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| otherwise = countTimes' ds (getDirection d $ m HMS.! ss) . succ
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solve :: String -> DataMap -> Int
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solve directions m = foldl1' lcm $ map (countTimes directions m) $ filter ((== 'A') . head) $ HMS.keys m
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getDataMap :: [String] -> DataMap
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getDataMap = HMS.fromList . map parseLine
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where
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revTake3 = reverse . take 3
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parseLine l = (revTake3 l, (revTake3 $ drop 7 l, revTake3 $ drop 12 l))
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main :: IO ()
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main = do
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allLines <- lines <$> readFile "data.txt"
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let directions = cycle $ head allLines
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dataMap = getDataMap $ drop 2 allLines
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print $ solve directions dataMap
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