day13 part 1

part 2 doesn’t work, time to rewrite

2022/day13/day13.hs

@@ -0,0 +1,40 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.List
+import Data.List.Split
+import Data.Maybe
+import qualified Data.Text as T
+
+main :: IO ()
+main = do
+  input <- map lines . splitOn "\n\n" <$> readFile "input"
+  let toDigit = T.unpack . T.replace "10" ":" . T.pack
+  print $
+    sum $ zipWith (*) [1 ..] $ map (fromEnum . isOrdered 0 . map toDigit) input
+  let divider = ["[[6]]", "[[2]]"]
+  let sorted = sortBy mySort (divider ++ concat input)
+  print $ product $ map (+ 1) $ mapMaybe (`elemIndex` sorted) divider
+
+isOrdered :: Int -> [String] -> Bool
+isOrdered n [l:ls, r:rs]
+  | n < 0 && l == ',' = False
+  | n > 0 && r == ',' = True
+  | l == r = isOrdered n [ls, rs]
+  | l == ']' = (r /= ',') || isOrdered (succ n) [ls, r : rs]
+  | r == ']' = l == ',' && isOrdered (pred n) [l : ls, rs]
+  | l == '[' = r /= ']' && isOrdered (pred n) [ls, r : rs]
+  | r == '[' = l == ']' || isOrdered (succ n) [l : ls, rs]
+  | l == ',' = False
+  | r == ',' = True
+  | l > r = False
+  | l < r = True
+  | otherwise = False
+isOrdered _ [[], _] = True
+isOrdered _ [_, []] = False
+isOrdered _ _ = True
+
+mySort :: String -> String -> Ordering
+mySort x y =
+  if isOrdered 0 [x, y]
+    then LT
+    else GT