42 lines
1008 B
Haskell
42 lines
1008 B
Haskell
module Day02
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( day02_1,
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day02_2,
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)
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where
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import Control.Monad
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import Data.List (sort, sortBy)
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import Data.Ord
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isSafe :: [Int] -> Bool
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isSafe xs = (isAscending xs || isDescending xs) && maximum distances <= 3 && minimum distances >= 1
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where
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isAscending x = x == sort x
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isDescending x = x == sortBy (comparing Down) x
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distances = map abs $ zipWith (-) xs (drop 1 xs)
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removeLevel :: [Int] -> [[Int]]
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removeLevel xs = filter (\x -> length x == l) $ filterM (const [True, False]) xs
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where
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l = length xs - 1
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parseInput :: IO [[Int]]
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parseInput = do
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contents <- lines <$> readFile "input/day2.txt"
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let reports = map read . words <$> contents
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return reports
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day02_1 :: IO ()
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day02_1 = do
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reports <- parseInput
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putStrLn $
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"Day 2, Puzzle 1 solution: "
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++ show (length $ filter isSafe reports)
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day02_2 :: IO ()
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day02_2 = do
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reports <- parseInput
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putStrLn $
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"Day 2, Puzzle 2 solution: "
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++ show (length . filter (any isSafe) $ map removeLevel reports)
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