1 files changed, 94 insertions, 0 deletions
diff --git a/2021/day22/22b.hs b/2021/day22/22b.hs
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+++ b/2021/day22/22b.hs
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+module Main where
+
+import Text.Parsec
+import Data.Set (Set)
+import qualified Data.Set as S
+import Debug.Trace (trace)
+
+type Coord = (Int, Int, Int)
+data Cuboid = Cuboid Coord Coord deriving (Show, Eq)
+data Command = Command Bool Cuboid deriving (Show, Eq)
+
+onOff = toBool <$> (try (string "on") <|> string "off")
+  where toBool "on" = True
+        toBool _ = False
+
+number = do
+  sign <- (option '0' (char '-'))
+  num <- many1 digit
+  return $ read (sign : num)
+
+range = do
+  start <- number
+  string ".."
+  end <- number
+
+  return $ (start, end)
+
+parseLine = do
+  val <- onOff
+  string " x="
+  (sx, ex) <- range
+  string ",y="
+  (sy, ey) <- range
+  string ",z="
+  (sz, ez) <- range
+
+  let c = Cuboid (sx, sy, sz) (ex, ey, ez)
+  return $ Command val c
+parseFile = endBy parseLine (char '\n')
+
+intersects1D :: (Int, Int) -> (Int, Int) -> Bool
+intersects1D (a1, a2) (b1, b2) = a2 > b1 && b2 > a1
+
+zipCoords :: Coord -> Coord -> [(Int, Int)]
+zipCoords (x, y, z) (x', y', z') = [(x, x'), (y, y'), (z, z')]
+
+intersects :: Cuboid -> Cuboid -> Bool
+intersects (Cuboid s e) (Cuboid s' e') = any (uncurry intersects1D) (zip (zipCoords s e) (zipCoords s' e'))
+
+cEmpty :: Cuboid -> Bool
+cEmpty (Cuboid (sx, sy, sz) (ex, ey, ez)) = sx > ex || sy > ey || sz > ez
+
+cVolume :: Cuboid -> Int
+cVolume (Cuboid (sx, sy, sz) (ex, ey, ez)) = vx * vy * vz
+  where vx = abs (sx - (ex + 1))
+        vy = abs (sy - (ey + 1))
+        vz = abs (sz - (ez + 1))
+
+ccVolume :: ChargedCuboid -> Int
+ccVolume c | charge c = cVolume (cuboid c)
+           | otherwise = -(cVolume (cuboid c))
+
+cIntersection :: Cuboid -> Cuboid -> Cuboid
+cIntersection c1@(Cuboid s1 e1) c2@(Cuboid s2 e2) | not  $ intersects c1 c2 = nullCuboid
+                                                  | otherwise = (Cuboid s' e')
+                                                    where s' = map3 (uncurry max) (zip3t s1 s2)
+                                                          e' = map3 (uncurry min) (zip3t e1 e2)
+
+data ChargedCuboid = ChargedCuboid { charge :: Bool
+                                    ,cuboid :: Cuboid
+                                    } deriving (Show, Eq)
+
+performCommand :: [ChargedCuboid] -> Command -> [ChargedCuboid]
+performCommand cs (Command val c) | val = (ChargedCuboid val c) : (cs ++ overlaps)
+                                  | otherwise = cs ++ overlaps
+  where overlaps = filter (not . cEmpty . cuboid) $ map invertedIntersection cs
+        invertedIntersection cc = ChargedCuboid (not (charge cc)) ((cuboid cc) `cIntersection` c)
+
+nullCuboid :: Cuboid
+nullCuboid = Cuboid (0, 0, 0) ((-1), (-1), (-1))
+
+map3 :: (a -> b) -> (a, a, a) -> (b, b, b)
+map3 f (a, b, c) = (f a, f b, f c)
+
+zip3t :: (a, a, a) -> (b, b, b) -> ((a, b), (a, b), (a, b))
+zip3t (x, y, z) (x', y', z') = ((x, x'), (y, y'), (z, z'))
+
+main = do
+  input <- readFile "./input"
+  let (Right cmds) = parse parseFile "input" input
+
+  let cs = foldl performCommand [] cmds
+  let vol = foldr (+) 0 $ map ccVolume cs
+  print vol