45 lines
1.6 KiB
Haskell
45 lines
1.6 KiB
Haskell
module Day8_1 where
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import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
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import Data.Text (splitOn, unpack, pack)
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import Prelude hiding (splitAt)
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import Data.List (sort, (\\))
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splitAt :: String -> String -> [String]
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splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
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decode :: [String] -> [(String, Int)]
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decode nums = zip (head <$> [zero, one, two, three, four, five, six, seven, eight, nine]) [0..9]
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where
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one = withLength 2
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two = filter (not . all (`elem` head nine)) $ withLength 5
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three = withLength 5 \\ [head two, head five]
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four = withLength 4
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five = filter (all (`elem` head six)) $ withLength 5
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six = filter (\x -> not $ all (`elem` x) (head seven)) $ withLength 6
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seven = withLength 3
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eight = withLength 7
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nine = filter (\x -> all (`elem` x) (head four)) $ withLength 6
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zero = withLength 6 \\ [head nine, head six]
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--
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withLength y = filter ((== y) . length) nums
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decodeDigit :: [(String, Int)] -> String -> Int
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decodeDigit [] d = error "oh no"
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decodeDigit (x:xs) d
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| fst x == d = snd x
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| otherwise = decodeDigit xs d
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applyDecode :: [(String, Int)] -> [String] -> String
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applyDecode codes = concatMap (show . decodeDigit codes)
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main :: IO ()
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main = do
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input <- openFile "inputs/8.txt" ReadMode
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contents <- hGetContents input
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let patterns = map (map sort . splitAt " ") . splitAt " | " <$> lines contents
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let pairs = zip (head <$> patterns) ((!! 1) <$> patterns)
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print $ sum (read <$> map (\x -> applyDecode (decode $ fst x) (snd x)) pairs :: [Int])
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hClose input |