35 lines
1.0 KiB
Haskell
35 lines
1.0 KiB
Haskell
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module Day3 where
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import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
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import Data.List ( maximumBy, minimumBy, group, sort )
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import Data.Function (on)
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import Data.Char (digitToInt)
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column :: String -> Int -> String
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column str i = map (!! i) $ lines str
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columns :: String -> Int
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columns str = maximum $ map length $ lines str
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mostCommon :: String -> Char
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mostCommon str = head . maximumBy (compare `on` length) . group $ sort str
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leastCommon :: String -> Char
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leastCommon str = head . minimumBy (compare `on` length) . group $ sort str
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binaryToDecimal :: Int -> Int
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binaryToDecimal = foldl1 ((+) . (2 *)) . map digitToInt . show
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main :: IO ()
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main = do
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input <- openFile "inputs/3.txt" ReadMode
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contents <- hGetContents input
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let gamma = mostCommon . column contents <$> [0..(columns contents - 1)]
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let epsilon = leastCommon . column contents <$> [0..(columns contents - 1)]
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let energy = product (binaryToDecimal . read <$> [gamma, epsilon] :: [Int])
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print energy
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hClose input
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