72 lines
2 KiB
Haskell
72 lines
2 KiB
Haskell
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-- requires cabal install --lib megaparsec parser-combinators
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module Main (main) where
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import Control.Applicative.Permutations
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import Control.Monad (void, when)
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import Data.Char qualified as C
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import Data.Either
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import Data.Functor
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import Data.List qualified as L
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import Data.Map qualified as M
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import Data.Maybe
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import Data.Set qualified as S
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import Data.Vector qualified as V
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import Data.Void (Void)
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import Text.Megaparsec
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import Text.Megaparsec.Char
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import Debug.Trace
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exampleExpectedOutput = 374
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type Position = (Int, Int)
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type Input = [Position]
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type Parser = Parsec Void String
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parseLine :: Parser Position
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parseLine = do
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(SourcePos _ y x) <- getSourcePos
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void $ char '#' <* some (void (char '.') <|> void eol)
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return (unPos x, unPos y)
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parseInput' :: Parser Input
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parseInput' = do
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some (void (char '.') <|> void eol)
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some parseLine <* eof
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parseInput :: String -> IO Input
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parseInput filename = do
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input <- readFile filename
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case runParser parseInput' filename input of
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Left bundle -> error $ errorBundlePretty bundle
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Right input' -> return input'
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compute :: Input -> Int
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compute input = distances $ map expand input
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where
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distances :: Input -> Int
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distances [] = 0
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distances (x:xs) = distances' x xs + distances xs
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distances' :: Position -> Input -> Int
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distances' a [] = 0
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distances' a (x:xs) = distance a x + distances' a xs
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distance :: Position -> Position -> Int
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distance (x1, y1) (x2, y2) = abs (x2-x1) + abs (y2-y1)
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expand :: Position -> Position
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expand (x, y) = (x', y')
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where
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x' = x + 999999 * S.size (S.filter (< x) emptyCols)
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y' = y + 999999 * S.size (S.filter (< y) emptyRows)
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cols = S.fromList $ map fst input
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rows = S.fromList $ map snd input
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allCols = S.fromList [0..S.findMax cols]
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allRows = S.fromList [0..S.findMax rows]
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emptyCols = allCols S.\\ cols
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emptyRows = allRows S.\\ rows
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main :: IO ()
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main = do
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input <- parseInput "input"
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print $ compute input
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