27 lines
634 B
Haskell
Executable file
27 lines
634 B
Haskell
Executable file
#!/usr/bin/env runhaskell
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parseInput :: String -> [[Integer]]
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parseInput = map (map read . words) . lines
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solve str = show (part1', part2')
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where
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input = parseInput str
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part1' = part1 input
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part2' = part2 input
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part1 xs = sum $ map next xs
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part2 xs = sum $ map prev xs
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deltas xs = zipWith (flip (-)) xs $ tail xs
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differentiate xs = takeWhile notAllZeros $ iterate deltas xs
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where
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notAllZeros xs = not $ all (== 0) xs
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next xs = sum $ map last $ differentiate xs
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prev xs = foldl1 (flip (-)) $ reverse $ map head $ differentiate xs
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main :: IO ()
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main = do
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contents <- getContents
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putStrLn $ solve contents
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