36 lines
967 B
Haskell
36 lines
967 B
Haskell
import Data.List (foldl1')
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import qualified Data.HashMap.Strict as HMS
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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' _ ('Z':_) = id
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countTimes' (d:ds) ss@(s:_) = countTimes' ds (getDirection d $ m HMS.! ss)
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. succ
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solve :: String -> DataMap -> Int
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solve directions m = foldl1' lcm
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. map (countTimes directions m)
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. filter ((== 'A') . head)
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. HMS.keys
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$ 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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get3At x = reverse . take 3 . drop x
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parseLine l = (get3At 0 l, (get3At 7 l, get3At 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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print . solve directions . getDataMap . drop 2 $ allLines
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