DayTen.hs

DayTen.hs

{-# LANGUAGE OverloadedStrings #-}

module DayTen
    ( partOne
    ) where
import qualified Data.Text as T
import qualified Data.Text.IO as TI
import qualified Data.Maybe as M
import qualified Data.List as L
import qualified Data.Set as S
import qualified Data.List.Extra as LE
import qualified Control.Monad as CM

data Instruction = Noop | Add Int deriving (Show, Eq)

makeHistory instructions = (flatten $ L.unfoldr go (instructions, 1))
  where go ([], _) = Nothing
        go ((Noop:rest), runningTotal) = Just ([runningTotal], (rest, runningTotal))
        go (((Add n):rest), runningTotal) = Just ([runningTotal, runningTotal], (rest, runningTotal + n))
        flatten lists = L.concatMap identity lists
        identity x = x

testLines = map T.pack ["noop", "addx 3", "addx -5"]

parse lines = map parseLine lines
  where parseLine "noop" = Noop
        parseLine line = Add $ readText $ last $ T.split (== ' ') line
        readText = read . T.unpack

partOne lines = sum $ map getStrength indices
  where getStrength index = (history !! index) * index
        history = 0:(makeHistory lines)
        indices = [20,60,100,140,180,220]

screenWidth = 40

renderMegaLine spriteHistory = map renderCharAtCycle [0..((length spriteHistory) - 1)]
  where renderCharAtCycle c = isClose (spritePositionAt c) $ mod c screenWidth
        isClose a b = (abs (a - b)) <= 1
        spritePositionAt c = spriteHistory !! c

render spriteHistory = map renderLine (LE.chunksOf screenWidth (renderMegaLine spriteHistory))
  where renderLine line = map (\e -> if e then '#' else '.') line

partTwo path = do
  inputLines <- getLines path
  let linesToPrint = render $ makeHistory inputLines
  CM.forM_ linesToPrint print

getLines :: String -> IO [Instruction]
getLines path =
  do
    input <- TI.readFile path
    let inputLines = T.lines input
        parsed = parse inputLines
    return parsed