42 lines
1.3 KiB
Haskell
42 lines
1.3 KiB
Haskell
module Day12 where
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import Data.Map ( Map, fromList, unionWith, empty, (!) )
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import Data.List.Split (splitOn)
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import qualified Data.Char
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type Path = (String,String)
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type System = Map String [String]
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readPath :: String -> Path
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readPath s = (from,to) where [from,to] = splitOn "-" s
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addPath :: Path -> System -> System
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addPath (from,to) = unionWith (++) (Data.Map.fromList [(from,[to]), (to,[from])])
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isUpper :: String -> Bool
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isUpper = Data.Char.isUpper . head
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pathFinder :: System -> [String] -> [[String]]
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pathFinder sys p@("end":xs) = [p]
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pathFinder sys p@(x:xs) = concatMap (\next -> pathFinder sys (next:p)) elig
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where elig = filter (\cave -> isUpper cave || cave `notElem` p) (sys ! x)
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pathFinder2 :: System -> [String] -> [[String]]
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pathFinder2 sys p@("end":xs) = [p]
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pathFinder2 sys p@(x:xs) = concatMap (\next -> f next sys (next:p)) elig
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where
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f cave = if isUpper cave || cave `notElem` p then pathFinder2 else pathFinder
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elig = filter (/= "start") (sys ! x)
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main :: IO ()
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main = do
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input <- map readPath . lines <$> getContents
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let system = foldr addPath Data.Map.empty input
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putStrLn "part 1: "
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let paths = map reverse $ pathFinder system ["start"]
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print $ length paths
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putStrLn "part 2: "
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let paths = map reverse $ pathFinder2 system ["start"]
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print $ length paths
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