75 lines
1.8 KiB
Haskell
75 lines
1.8 KiB
Haskell
import System.IO
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( hClose, openFile, hGetContents, IOMode(ReadMode) )
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import Text.Parsec
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import Text.Parsec.String
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import Control.Monad
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import Data.List
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import Data.Maybe
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import Data.Sequence (replicate, Seq, mapWithIndex)
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import Data.Map (Map, (!))
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import qualified Data.Map as Map
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type Coord = (Int, Int)
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type LineEnds = (Coord, Coord)
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type Grid = Map Coord Integer
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int :: Parser Int
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int = read <$> many1 digit
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eol :: Parser ()
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eol = void $ char '\n'
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coord :: Parser Coord
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coord = do
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x <- int
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char ','
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y <- int
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return (x, y)
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arrow :: Parser ()
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arrow = void $ string " -> "
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line :: Parser LineEnds
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line = do
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from <- coord
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arrow
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to <- coord
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return (from, to)
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inputParser :: Parser [LineEnds]
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inputParser = line `endBy1` eol
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lineToCellList :: LineEnds -> [Coord]
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lineToCellList ((x0, y0), (x1, y1))
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| x0 == x1 = [ (x0, y) | y <- [min y0 y1 .. max y0 y1] ]
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| y0 == y1 = [ (x, y0) | x <- [min x0 x1 .. max x0 x1] ]
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| otherwise = [ (x, y) | x <- [min x0 x1 .. max x0 x1],
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y <- [min y0 y1 .. max y0 y1],
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abs (x - x0) == abs (y - y0) ]
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type CoordMap = Map Coord Int
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scoreFold :: Coord -> (CoordMap, Int) -> (CoordMap, Int)
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scoreFold coord (map, acc)
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| Map.member coord map = if
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(map ! coord) == 1 then (Map.adjust (+1) coord map, acc + 1)
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else (Map.adjust (+1) coord map, acc)
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| otherwise = (Map.insert coord 1 map, acc)
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score :: [LineEnds] -> Int
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score les = snd (foldr scoreFold (Map.empty, 0) coords)
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where
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coords = concatMap lineToCellList les
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main = do
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handle <- openFile "input.txt" ReadMode
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contents <- hGetContents handle
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case parse inputParser "" contents of
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Left x -> print x
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Right x -> print (score x)
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hClose handle
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