40 lines
1 KiB
Haskell
40 lines
1 KiB
Haskell
module Day2 where
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import AoC
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import Data.Char
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import Data.Maybe
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import Text.ParserCombinators.ReadP
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import Text.Read.Lex
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data Line = Line
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{ num1 :: Int
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, num2 :: Int
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, letter :: Char
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, password :: String
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}
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instance Show Line where
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show (Line num1 num2 letter password) = show num1 ++ "-" ++ show num2 ++ " " ++ [letter] ++ ": " ++ password
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parseLine :: ReadP Line
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parseLine = do
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num1 <- readDecP
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string "-"
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num2 <- readDecP
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string " "
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letter <- get
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string ": "
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password <- munch1 $ const True
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eof
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return (Line num1 num2 letter password)
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valid_1 :: Line -> Bool
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valid_1 (Line min max letter password) = within min max $ length $ filter (== letter) password
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where within x y z = x <= z && z <= y
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valid_2 :: Line -> Bool
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valid_2 (Line pos1 pos2 letter password) = (matchesAt pos1) /= (matchesAt pos2)
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where matchesAt pos = password !! (pos-1) == letter
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main = runAoC (map (fromJust . oneCompleteResult parseLine) . lines) (length . filter valid_1) (length . filter valid_2)
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