Day 10B solution

day10b/src/Main.hs

@@ -9,12 +9,15 @@ import Data.Bifunctor (first, second)
 import Data.Bits (Bits (..))
 import Data.Foldable (find)
 import Data.Map qualified as M
-import Data.Maybe (catMaybes, fromJust, fromMaybe, isJust)
-import Data.Set qualified as S
+import Data.Maybe (catMaybes, fromJust, fromMaybe)
+import GHC.OldList (intercalate)
 
 parsePipe :: Char -> Integer
 parsePipe = fromMaybe 0 . (M.fromList (zip "|-JLF7S" [0b1100, 0b0011, 0b1010, 0b1001, 0b0101, 0b0110, 0b1111]) M.!?)
 
+toPipe :: Integer -> Char
+toPipe = fromMaybe '.' . (M.fromList (zip [0b1100, 0b0011, 0b1010, 0b1001, 0b0101, 0b0110, 0b1111] "┃━┛┗┏┓╋") M.!?)
+
 flipDirs :: Integer -> Integer
 flipDirs =
   sum
@@ -38,14 +41,35 @@ main = do
           $ c
 
   let start = fst . fromJust $ find ((== 0b1111) . snd) (M.assocs pipes)
-  let path = (start :) . takeWhile (/= start) . (fst <$>) . tail $ iterate (head . filter ((/= 0) . snd) . findAdj) (start, 0b1111)
+  let pipeStart = sum 
+        $ flip (zipWith ((*) . toInteger . fromEnum)) [0b0010, 0b0001, 0b1000, 0b0100] 
+        $ flip elem (fst <$> findAdj (start, 0b1111)) 
+        <$> (($ start) <$> ([first, second] <*> [(-1 +), (1 +)])) 
 
-  let go v (((> 0) . (.&. 0b1100) -> True) : xs) = go (not v) xs
-      go v (_ : xs) = fromEnum v + go v xs
-      go _ [] = 0
+  let path = 
+        ((start, 0b1111) :)
+        . takeWhile ((/= start) . fst) 
+        . tail 
+        $ iterate (head . filter ((/= 0) . snd) . findAdj) (start, pipeStart)
 
-  let pathPipes = S.fromList path
-  let piping = [[fromMaybe 0 $ S.lookupIndex (x, y) pathPipes *> (pipes M.!? (x, y)) | x <- [0 .. maximum $ length <$> lns]] | y <- [0 .. length lns]]
+  let countSpaces = go 0 False
+        where
+            go _ v (0b1100 : xs) = go 0 (not v) xs
+            go p v (0b0011 : xs) = go p v xs
+            go _ v (0 : xs) = fromEnum v + go 0 v xs
+            go p v (x : xs) 
+              | p == 0 = go x v xs
+              | p .&. x .&. 0b1100 > 0 = go 0 v xs
+              | otherwise = go 0 (not v) xs
+            go _ _ [] = 0
 
-  print $ piping
-  print $ sum $ go False <$> piping
+  let pathPipes = M.fromList path
+  let piping = [[
+          (\c -> if c == 0b1111 then pipeStart else c) 
+          $ fromMaybe 0 
+          $ pathPipes M.!? (x, y) 
+          *> pipes M.!? (x, y) 
+        | x <- [0 .. maximum (length <$> lns) - 1]] | y <- [0 .. length lns - 1]]
+
+  putStrLn $ intercalate "\n" $ flip (zipWith (++)) (show . countSpaces <$> piping) $ fmap toPipe <$> piping
+  print $ sum $ countSpaces <$> piping

day10b/test.txt

@@ -1,10 +1,10 @@
-.F----7F7F7F7F-7....
-.|F--7||||||||FJ....
-.||.FJ||||||||L7....
-FJL7L7LJLJ||LJ.L-7..
-L--J.L7...LJS7F-7L7.
-....F-J..F7FJ|L7L7L7
-....L7.F7||L7|.L7L7|
-.....|FJLJ|FJ|F7|.LJ
-....FJL-7.||.||||...
-....L---J.LJ.LJLJ...
+FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L