45 lines
1.3 KiB
Haskell
45 lines
1.3 KiB
Haskell
import Data.Either (rights)
|
|
import Data.Map qualified as M
|
|
import Data.Text qualified as T
|
|
import Lib (readFile')
|
|
import Text.Parsec
|
|
|
|
main :: IO ()
|
|
main = do
|
|
(directionsRaw : _ : mapsRaw) <- T.lines <$> readFile' "day08.in"
|
|
let directions = cycle $ T.unpack directionsRaw
|
|
let maps' = rights $ map (parse parseMap "") mapsRaw
|
|
let maps = M.fromList maps'
|
|
|
|
putStr "Q1: "
|
|
print $ zzz directions maps 0 "AAA"
|
|
|
|
putStr "Q2: "
|
|
print . foldl1 lcm . map (xxz directions maps 0) . filter (\[_, _, c] -> c == 'A') . map fst $ maps'
|
|
|
|
-- dumb and good recursion
|
|
zzz :: String -> M.Map String (String, String) -> Int -> String -> Int
|
|
zzz (d : ds) m acc str
|
|
| next == "ZZZ" = acc + 1
|
|
| otherwise = zzz ds m (acc + 1) next
|
|
where
|
|
Just (left, right) = M.lookup str m
|
|
next = if d == 'L' then left else right
|
|
|
|
xxz :: String -> M.Map String (String, String) -> Int -> String -> Int
|
|
xxz (d : ds) m acc str
|
|
| [_, _, 'Z'] <- next = acc + 1
|
|
| otherwise = xxz ds m (acc + 1) next
|
|
where
|
|
Just (left, right) = M.lookup str m
|
|
next = if d == 'L' then left else right
|
|
|
|
-- Parsing --
|
|
|
|
parseMap :: (Stream s m Char) => ParsecT s u m (String, (String, String))
|
|
parseMap = do
|
|
a <- many1 letter <* string " = ("
|
|
b <- many1 letter <* string ", "
|
|
c <- many1 letter <* char ')'
|
|
return (a, (b, c))
|