49 lines
1.5 KiB
Haskell
49 lines
1.5 KiB
Haskell
module Day5 where
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import System.IO (openFile, IOMode (ReadMode), hClose, hGetContents)
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import Data.Text (splitOn, unpack, pack)
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import Prelude hiding (splitAt)
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import Data.List (sort, intersect)
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type Coordinate = (Int, Int)
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type Range = ([Int], [Int])
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toCoord :: String -> Coordinate
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toCoord str = (x, y)
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where
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xy = splitAt "," str
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x = read $ head xy
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y = read $ xy !! 1
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isStraight :: Coordinate -> Coordinate -> Bool
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isStraight c1 c2 = fst c1 == fst c2 || snd c1 == snd c2
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splitAt :: String -> String -> [String]
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splitAt delimiter str = map unpack $ splitOn (pack delimiter) $ pack str
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coordsToRange :: (Coordinate, Coordinate) -> Range
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coordsToRange (a, b) = ([fst a..fst b], [snd a.. snd b])
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points :: Range -> [Coordinate]
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points range = [ (i,j) | i <- fst range, j <- snd range ]
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intersections :: [Range] -> [[Coordinate]]
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intersections [] = []
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intersections (x:xs) = map (\y -> points x `intersect` points y) xs ++ intersections xs
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dedup :: Eq a => [(a, a)] -> [(a, a)]
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dedup [] = []
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dedup (x:xs) = x : dedup (filter (x /=) xs)
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main :: IO ()
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main = do
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input <- openFile "inputs/5.txt" ReadMode
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contents <- hGetContents input
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let coords = map toCoord . splitAt " -> " <$> lines contents
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-- remove lines that aren't horizontal/vertical and sort them
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let lines = map sort $ filter (\x -> isStraight (head x) (x !! 1)) coords
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let pairs = map (coordsToRange . (\x -> (head x, x !! 1))) lines
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print . length . dedup . concat $ intersections pairs
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hClose input |