Day 16

day16/Part2.hs

@@ -0,0 +1,18 @@
+module Part2 where
+
+import Commons
+import Data.Set (empty, map, toList, delete)
+import Data.Array (bounds)
+
+
+getEnergized :: (Int, Int, Direction) -> Cavern -> [(Int, Int)]
+getEnergized (y0, x0, d) = toList . delete (y0, x0) . Data.Set.map (\ (y, x, _) -> (y, x)) . lightBeam (y0, x0) d empty
+
+getStarts :: Cavern -> [(Int, Int, Direction)]
+getStarts c = [(y, 0, East) | y <- [1..(fst (snd $ bounds c))]]
+              ++ [(y, 1 + snd (snd $ bounds c), West) | y <- [1..(fst (snd $ bounds c))]]
+              ++ [(0, x, South) | x <- [1..(snd (snd $ bounds c))]]
+              ++ [(1 + fst (snd $ bounds c), x, North) | x <- [1..(snd (snd $ bounds c))]]
+
+getMaxEnergized :: Cavern -> Int
+getMaxEnergized c = maximum (Prelude.map (\s -> length $ getEnergized s c) $ getStarts c)