Refactor code

src/Day08.hs

@@ -0,0 +1,80 @@
+module Day08
+  ( day08_1,
+    day08_2,
+  )
+where
+
+import Control.Applicative
+import Data.Bifunctor (bimap)
+import Data.List (uncons)
+import Data.Maybe (fromJust)
+import Data.Set (fromList)
+
+type Freq = Char
+
+type Coords = (Int, Int)
+
+data Antenna = Antenna
+  { frequency :: Freq,
+    coordinates :: Coords
+  }
+  deriving (Show, Eq)
+
+readAntenna :: Freq -> Coords -> Antenna
+readAntenna freq coords = Antenna {frequency = freq, coordinates = coords}
+
+getAntennas :: [String] -> [Antenna]
+getAntennas grid = concat . getZipList $ getAntennasRow <$> ZipList [0 ..] <*> ZipList grid
+  where
+    getAntennasRow n row = [readAntenna x (n, y) | (x, y) <- zip row [0 ..], x /= '.']
+
+isInside :: Coords -> Int -> Int -> Bool
+isInside c x y = fst c >= 0 && fst c < x && snd c >= 0 && snd c < y
+
+generateCoords :: Coords -> Coords -> [Coords]
+generateCoords c offset = scanl shiftCoords c (repeat offset)
+  where
+    shiftCoords x = bimap (fst x +) (snd x +)
+
+getAntinodes :: Antenna -> Antenna -> Int -> Int -> [Coords]
+getAntinodes a b maxX maxY =
+  let xa = fst $ coordinates a
+      ya = snd $ coordinates a
+      xb = fst $ coordinates b
+      yb = snd $ coordinates b
+   in if frequency a /= frequency b || coordinates a == coordinates b
+        then []
+        else filter (\c -> isInside c maxX maxY) [(2 * xa - xb, 2 * ya - yb), (2 * xb - xa, 2 * yb - ya)]
+
+getAntinodes' :: Antenna -> Antenna -> Int -> Int -> [Coords]
+getAntinodes' a b maxX maxY =
+  let xa = fst $ coordinates a
+      ya = snd $ coordinates a
+      xb = fst $ coordinates b
+      yb = snd $ coordinates b
+      distX = xa - xb
+      distY = ya - yb
+   in if frequency a /= frequency b || coordinates a == coordinates b
+        then []
+        else
+          filter (\c -> isInside c maxX maxY) [(2 * xa - xb, 2 * ya - yb), (2 * xb - xa, 2 * yb - ya)]
+            ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (distX, distY))
+            ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (-distX, -distY))
+
+day08_1 :: IO ()
+day08_1 = do
+  contents <- lines <$> readFile "input/day8.txt"
+  let antennas = getAntennas contents
+      x = length contents
+      y = length $ fst . fromJust $ uncons contents
+      antinodes = fromList $ concat [getAntinodes a b x y | a <- antennas, b <- antennas, a /= b, frequency a == frequency b]
+  putStrLn $ "Day 8, Puzzle 1 solution: " ++ show (length antinodes)
+
+day08_2 :: IO ()
+day08_2 = do
+  contents <- lines <$> readFile "input/day8.txt"
+  let antennas = getAntennas contents
+      x = length contents
+      y = length $ fst . fromJust $ uncons contents
+      antinodes = fromList $ concat [getAntinodes' a b x y | a <- antennas, b <- antennas, a /= b, frequency a == frequency b]
+  putStrLn $ "Day 8, Puzzle 2 solution: " ++ show (length antinodes)