23 lines
696 B
Haskell
23 lines
696 B
Haskell
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import Aoc ( aocMain )
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parseFile :: [String] -> [[Int]]
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parseFile = map (map read . words)
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part1 :: [[Int]] -> Int
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part1 reports =
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length $ filter isSafe $ map differences reports
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where
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differences xs = zipWith (-) xs (tail xs)
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isGradual dx = 1 <= abs dx && abs dx <= 3
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isSafe dxs = all isGradual dxs && (all (<0) dxs || all (>0) dxs)
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part2 :: [[Int]] -> Int
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part2 reports =
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length $ filter isSafe $ map remove1 reports
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where
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remove n xs = let (front, back) = splitAt n xs in front ++ tail back
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remove1 report = map (`remove` report) [0..length report-1]
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isSafe = (>0) . part1
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main :: IO ()
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main = aocMain parseFile part1 part2
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