Day 10

src/Day10.hs

@@ -0,0 +1,79 @@
+module Day10
+  ( Instruction (..),
+    parseProgram,
+    signalStrength,
+    executeProgram,
+    draw,
+    isSpriteDrawn,
+    day10
+  )
+where
+
+import Control.Arrow ((>>>))
+import qualified Data.Matrix as M
+import Debug.Trace (trace)
+import Data.List.Split (chunksOf)
+import Data.List (intercalate)
+
+data Instruction = Addx Int | Noop
+  deriving (Show, Eq)
+
+newtype Pixel = Pixel Bool deriving (Eq)
+
+instance Show Pixel where
+  show (Pixel True) = "▓"
+  show (Pixel False) = "░"
+
+
+type CRT = String
+
+parseProgram :: String -> [Instruction]
+parseProgram = lines >>> map parseProgram'
+  where
+    parseProgram' :: String -> Instruction
+    parseProgram' "noop" = Noop
+    parseProgram' line = splitAt 4 >>> snd >>> read >>> Addx $ line
+
+
+isSpriteDrawn :: Int -> Int -> Bool
+isSpriteDrawn x p = abs (position - x) <= 1
+  where
+    position = p `mod` 40
+
+draw :: [Int] -> CRT
+draw registerValues = unlines lastPicture
+  where
+    pictures = zipWith isSpriteDrawn registerValues [0..]
+    lastPicture = concatMap (show . Pixel) >>> chunksOf 40 $ pictures
+
+
+
+signalStrength :: [Int] -> Int
+signalStrength e = start + sum computedRest
+  where
+    start = e !! 20 * 20
+    rest = drop 20 e
+    withCycle = zip [60, 100..] (every 40 rest)
+    computedRest = [c*r | (c,r) <- withCycle]
+
+every :: Int -> [a] -> [a]
+every n xs = case drop (n-1) xs of
+              y : ys -> y : every n ys
+              [] -> []
+
+executeProgram :: [Instruction] -> [Int]
+executeProgram = scanl (+) 1 . concatMap execOne
+  where
+    execOne instruction = case instruction of
+        Noop   -> [0]
+        Addx x -> [0, x]
+
+day10 :: IO ()
+day10 = do
+  input <- readFile "ressources/day10-input"
+  putStrLn "Day10"
+  let states = parseProgram >>> executeProgram $ input
+  let signal = signalStrength states
+  let crt = draw states
+  putStrLn ("Signal strength: " ++ show signal)
+  putStrLn ("CRT picture: \n" ++ crt)

src/Lib.hs

@@ -11,9 +11,10 @@ import Day6 (day6)
 import Day7 (day7)
 import Day8 (day8)
 import Day9 (day9)
+import Day10 (day10)
 
 days :: [IO ()]
-days = [day1, day2, day3, day4, day5, day6, day7, day8, day9]
+days = [day1, day2, day3, day4, day5, day6, day7, day8, day9, day10]
 
 sep :: IO ()
 sep = putStrLn "---------"