2015 Day 06 in Haskell

2015/day06/day06.hs

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+import Aoc
+import Data.List.Split ( splitOn )
+
+parseFile :: [String] -> [(String, (Int, Int), (Int, Int))]
+parseFile = map (\line ->
+    let line' = words line in
+    let (command, [pos1, "through", pos2]) = splitAt (length line' - 3) line' in
+    (unwords command, pos pos1, pos pos2))
+    where pos = pair . map read . splitOn ","
+
+doCommands :: (a -> String -> a) -> a -> [(String, (Int, Int), (Int, Int))] -> (Int, Int) -> a
+doCommands doCommand start commands pos = foldl (doCommand' pos) start commands
+    where
+        within (x0, y0) (x1, y1) (x, y) = x0 <= x && x <= x1 && y0 <= y && y <= y1
+        doCommand' pos state (command, pos1, pos2) = if within pos1 pos2 pos then doCommand state command else state
+
+
+part1 :: [(String, (Int, Int), (Int, Int))] -> Int
+part1 commands = length $ filter isOn [(x, y) | x <- [0..999], y <- [0..999]]
+    where
+        doCommand state "turn off" = False
+        doCommand state "turn on" = True
+        doCommand state "toggle" = not state
+
+        isOn = doCommands doCommand False commands
+
+
+part2 :: [(String, (Int, Int), (Int, Int))] -> Int
+part2 commands = sum [brightness (x, y) | x <- [0 .. 999], y <- [0 .. 999]]
+    where
+        doCommand state "turn off" = max 0 (state - 1)
+        doCommand state "turn on" = state + 1
+        doCommand state "toggle" = state + 2
+
+        brightness = doCommands doCommand 0 commands
+
+main :: IO ()
+main = aocMain parseFile part1 part2