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20 lines
659 B
Haskell
20 lines
659 B
Haskell
module Y2020.Day10 (y20day10) where
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import Data.List
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sliding :: [Int] -> [(Int, Int)]
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sliding (x1:x2:xs) = ((x1, x2):(sliding (x2:xs)))
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sliding (x1:[]) = ((x1, x1+3):[])
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sliding [] = []
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combinations :: Int -> Int
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combinations n = nb !! n
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where nb = [1, 1, 2, 4, 7, 13]
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y20day10 :: [String] -> (String, String)
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y20day10 input = (part1, part2)
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where part1 = show $ product $ map length $ group $ filter (/= 2) $ sort $ diffs
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part2 = show $ product $ map (combinations . length) $ filter (\(x:_) -> x /= 3) $ group $ diffs
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input' = sort $ map read input :: [Int]
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diffs = map (\(a, b) -> b - a) $ (0, head input'):(sliding input')
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