82 lines
2.0 KiB
Haskell
82 lines
2.0 KiB
Haskell
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{-# LANGUAGE ImportQualifiedPost #-}
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module Days.D18 where
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import Common
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import Data.Set (Set)
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import Data.Set qualified as Set
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import Data.Tuple.Extra (uncurry3)
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import Parse
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import Text.Megaparsec.Char (char)
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parser :: Parser [(Int, Int, Int)]
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parser = someLines point
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where
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point = (,,) <$> int <* char ',' <*> int <* char ',' <*> int
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mins :: [(Int, Int, Int)] -> (Int, Int, Int)
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mins =
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foldr1
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(\(a', b', c') (a, b, c) -> (min a' a, min b' b, min c' c))
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maxs :: [(Int, Int, Int)] -> (Int, Int, Int)
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maxs =
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foldr1
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(\(a', b', c') (a, b, c) -> (max a' a, max b' b, max c' c))
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adjacent :: (Int, Int, Int) -> [(Int, Int, Int)]
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adjacent (x, y, z) =
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[ (x - 1, y, z),
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(x + 1, y, z),
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(x, y - 1, z),
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(x, y + 1, z),
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(x, y, z - 1),
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(x, y, z + 1)
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]
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part1 :: [(Int, Int, Int)] -> Int
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part1 l =
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let s = Set.fromList l
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in length
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. filter (\v -> not $ Set.member v s)
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. concatMap adjacent
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$ l
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part2 :: [(Int, Int, Int)] -> Int
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part2 points =
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let (x_max, y_max, z_max) = maxs points
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(x_min, y_min, z_min) = mins points
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insideSearchSpace (x, y, z) =
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x_min - 1 <= x
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&& x <= x_max + 1
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&& y_min - 1 <= y
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&& y <= y_max + 1
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&& z_min - 1 <= z
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&& z <= z_max + 1
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start = (x_min - 1, y_min - 1, z_min - 1)
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in go insideSearchSpace [start] (Set.singleton start) 0
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where
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pointSet :: Set (Int, Int, Int)
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pointSet = Set.fromList points
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go _ [] _ result = result
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go inside active_ seen_ result_ =
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uncurry3 (go inside)
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. foldr
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( \p (active, seen, result) ->
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if Set.member p seen
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then (active, seen, result)
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else
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if Set.member p pointSet
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then (active, seen, result + 1)
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else (p : active, Set.insert p seen, result)
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)
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([], seen_, result_)
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. filter inside
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. concatMap adjacent
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$ active_
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day :: Day
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day = parsecDay parser (definitive . part1, definitive . part2)
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