54 lines
1.4 KiB
Haskell
54 lines
1.4 KiB
Haskell
module Day10 where
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import Data.Maybe
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import Data.List (sort)
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import Control.Monad (foldM)
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closing :: Char -> Maybe Char
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closing '(' = Just ')'
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closing '[' = Just ']'
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closing '{' = Just '}'
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closing '<' = Just '>'
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closing _ = Nothing
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score :: Char -> Maybe Int
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score ')' = Just 3
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score ']' = Just 57
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score '}' = Just 1197
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score '>' = Just 25137
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score _ = Nothing
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closingScore :: Char -> Int
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closingScore ')' = 1
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closingScore ']' = 2
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closingScore '}' = 3
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closingScore '>' = 4
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calcScore :: String -> Int
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calcScore xs = foldr (\char score -> score*5 + closingScore char) 0 (reverse xs)
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getInvalidChar :: [Char] -> String -> Char
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getInvalidChar _ [] = ' '
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getInvalidChar st (x:xs)
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| x `elem` "([{<" = getInvalidChar (x:st) xs
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| otherwise = if Just x == (listToMaybe st >>= closing) then getInvalidChar (tail st) xs else x
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getCompletionString :: [Char] -> String -> String
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getCompletionString st [] = map (fromJust . closing) st
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getCompletionString st (x:xs)
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| x `elem` "([{<" = getCompletionString (x:st) xs
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| otherwise = if Just x == (listToMaybe st >>= closing) then getCompletionString (tail st) xs else ""
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main :: IO ()
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main = do
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input <- lines <$> getContents
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putStr "part 1: "
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let chars = mapMaybe (score . getInvalidChar []) input
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print $ sum chars
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putStr "part 2: "
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let compls = filter (> 0) $ map (calcScore . getCompletionString []) input
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print $ sort compls !! (length compls `div` 2) |