From 3dda0ec7cb4477259a1be52565fe27e0312b9d3b Mon Sep 17 00:00:00 2001 From: tzlil Date: Fri, 15 Dec 2023 19:34:05 +0200 Subject: wip 5 --- 3/1.hs | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 3/1.hs (limited to '3/1.hs') diff --git a/3/1.hs b/3/1.hs new file mode 100644 index 0000000..1651ace --- /dev/null +++ b/3/1.hs @@ -0,0 +1,48 @@ +import Text.Parsec.String (Parser) +import Text.Parsec +import System.Environment +import Control.Monad +import Debug.Trace + +data Tile = EmptyT | Digit Int | Symbol deriving (Show,Eq) + +tile :: Parser Tile +tile = char '.' *> pure EmptyT <|> Digit <$> (read.pure <$> digit) <|> noneOf "\n" *> pure Symbol + +board = sepBy (many1 tile) newline + +symbolPositions l = [(x,y) | (y,r) <- zip [0..] l, (x,Symbol) <- zip [0..] r] + +digitPositions l = [(n,x,y) | (y,r) <- zip [0..] l, (x,Digit n) <- zip [0..] r] + +groupBy :: (a -> a -> Bool) -> [a] -> [[a]] +groupBy p = map (uncurry (:)) . groupByNonEmpty p + +groupByNonEmpty :: (a -> a -> Bool) -> [a] -> [(a,[a])] +groupByNonEmpty p = + foldr + (\x0 yt -> + let (xr,yr) = + case yt of + (x1,xs):ys -> + if p x0 x1 + then (x1:xs,ys) + else ([],yt) + [] -> ([],yt) + in (x0,xr):yr) + [] + +fromDigits :: [Int] -> Int +fromDigits = foldl ((+) . (10 *)) 0 + +neighbours = foldMap (\(x,y) -> map (\(dx,dy) -> (x+dx,y+dy)) neigh) where + neigh = liftM2 (,) [1,0,-1] [1,0,-1] + +solution :: [[Tile]] -> Int +solution board = sum $ map (fromDigits.map (\(n,_,_) -> n)) partNumbers where + blacklisted = neighbours $ symbolPositions board + digs = groupBy (\(_,x1,_) (_,x2,_) -> x2 == succ x1) $ digitPositions board + partNumbers = filter (\l -> any (\(_,x,y) -> (x,y) `elem` blacklisted) l) $ digs + + +main = liftM2 (>>=) readFile (((print . solution . either (error.show) id) .) . parse board) =<< head <$> getArgs \ No newline at end of file -- cgit 1.4.1