49 lines
1.3 KiB
Haskell
49 lines
1.3 KiB
Haskell
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import Aoc
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import Data.List.Split ( splitOn )
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import Data.List ( transpose )
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horizontal :: [String] -> Int
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horizontal = sum . map horizontal'
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where
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count word = pred . length . splitOn word
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horizontal' line = count "XMAS" line + count "SAMX" line
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sheer :: [String] -> [String]
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sheer [] = []
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sheer (x:xs) = x:(map ('.':) $ sheer xs)
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part1 :: [String] -> Int
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part1 board = horizontal board + vertical board + diagonal1 board + diagonal2 board
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where
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vertical = horizontal . transpose
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diagonal1 = vertical . sheer
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diagonal2 = diagonal1 . reverse
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kernelMapRow :: ([[a]] -> b) -> [a] -> [a] -> [a] -> [b]
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kernelMapRow kernel
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(a:r0@(b:c:_))
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(d:r1@(e:f:_))
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(g:r2@(h:i:_)) =
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kernel [[a,b,c],[d,e,f],[g,h,i]] : kernelMapRow kernel r0 r1 r2
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kernelMapRow _ [_, _] [_, _] [_, _] = []
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kernelMap :: ([[a]] -> b) -> [[a]] -> [[b]]
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kernelMap kernel (a:rest@(b:c:_)) = kernelMapRow kernel a b c : kernelMap kernel rest
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kernelMap _ [_, _] = []
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isXMAS :: [[Char]] -> Bool
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isXMAS [
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[a, _, b],
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[_, 'A', _],
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[c, _, d]] = isMS a d && isMS b c
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where
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isMS 'M' 'S' = True
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isMS 'S' 'M' = True
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isMS _ _ = False
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isXMAS [[_, _, _], [_, _, _], [_, _, _]] = False
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part2 :: [String] -> Int
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part2 = sum . map (length . filter id) . kernelMap isXMAS
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main :: IO ()
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main = aocMain id part1 part2
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