Day 6

.gitignore

@@ -1,3 +1,5 @@
 result*
 *.cabal
 dist-newstyle
+*.eventlog
+*.prof

Main.hs

@@ -7,17 +7,20 @@ import Day2
 import Day3
 import Day4
 import Day5
+import Day6
 
 main :: IO ()
 main = do
   putStrLn "AoC 2024"
-  putStrLn "Day 1"
+  --putStrLn "Day 1"
-  Day1.main
+  --Day1.main
-  putStrLn "Day 2"
+  --putStrLn "Day 2"
-  Day2.main
+  --Day2.main
-  putStrLn "Day 3"
+  --putStrLn "Day 3"
-  Day3.main
+  --Day3.main
-  putStrLn "Day 4"
+  --putStrLn "Day 4"
-  Day4.main
+  --Day4.main
-  putStrLn "Day 5"
+  --putStrLn "Day 5"
-  Day5.main
+  --Day5.main
+  putStrLn "Day 6"
+  Day6.main

inputs/day6.input

@@ -0,0 +1,130 @@
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package.yaml

@@ -1,28 +1,38 @@
 name: aoc24
 
-ghc-options: -Wall -threaded #-prof -fprof-auto -rtsopts
+ghc-options: -Wall -threaded
 
 default-extensions:
   - OverloadedStrings
 
 dependencies:
   - base == 4.*
+  - algebraic-graphs
+  - async
   - attoparsec
   - bytestring
-  - matrix
-  - vector
   - containers
-  - text
+  - hashable
-  - scientific
+  - matrix
-  - utility-ht
+  - parallel
   - safe
-  - algebraic-graphs
+  - scientific
+  - text
+  - unliftio
+  - unordered-containers
+  - utility-ht
+  - vector
 
 executables:
   aoc24:
     main: Main.hs
     dependencies:
       - aoc24
+  aoc24-debug:
+    main: Main.hs
+    ghc-options: -Wall -threaded -rtsopts -eventlog -prof #-fprof-auto
+    dependencies:
+      - aoc24
 
 library:
   source-dirs: src
@@ -32,7 +42,7 @@ library:
     - Day3
     - Day4
     - Day5
-    # - Day6
+    - Day6
     # - Day7
     # - Day8
     # - Day9

src/Day6.hs

@@ -0,0 +1,197 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE DeriveGeneric #-}
+
+module Day6 where
+
+-- import Data.Attoparsec.Text (Parser)
+-- import Data.Either (fromRight)
+-- import Data.List (find)
+-- import Data.List.HT (shearTranspose)
+-- import Data.Maybe (catMaybes)
+-- import qualified Data.Attoparsec.Text as P
+import Control.Parallel.Strategies
+import Data.List (intersperse, unfoldr, sort)
+import Data.Maybe (fromJust)
+import Data.Text (Text)
+import Debug.Trace
+import GHC.Generics (Generic)
+import Data.Hashable
+import qualified Data.List.NonEmpty as NE
+import qualified Data.Text as T
+import qualified Data.Text.IO as T
+import qualified Data.Vector as V
+import qualified Data.HashSet as H
+-- import UnliftIO (mapConcurrently)
+
+data MapObjects = MOEmpty | MOObstacle | MOExtraObstacle
+                | MOGuard GuardDirection
+  deriving Eq
+
+data GuardDirection = GDNorth | GDEast | GDSouth | GDWest
+  deriving (Show,Eq,Generic)
+
+instance Hashable GuardDirection
+
+s :: GuardDirection -> GuardDirection
+s GDNorth  = GDEast
+s GDEast   = GDSouth
+s GDSouth  = GDWest
+s GDWest   = GDNorth
+
+instance Show MapObjects where
+  show MOEmpty             = "."
+  show MOObstacle          = "#"
+  show MOExtraObstacle     = "O"
+  show (MOGuard GDNorth)   = "^"
+  show (MOGuard GDEast)    = ">"
+  show (MOGuard GDSouth)   = "v"
+  show (MOGuard GDWest)    = "<"
+
+prettyLine :: V.Vector MapObjects -> String
+prettyLine = intersperse ' ' . fmap (head . show) . reverse . V.toList
+
+prettyMap :: AoCMap -> String
+prettyMap (AoCMap (xmax,ymax) v) = go (xmax,ymax) (V.reverse v)
+  where
+    go (_,0) _ = ""
+    go (xmax',ymax') v' = prettyLine cur <> "\n" <> go (xmax',ymax'-1) next
+      where
+        (cur,next) = V.splitAt xmax' v'
+
+data AoCMap = AoCMap { getBounds :: Bounds, getObjects :: V.Vector MapObjects }
+  deriving Show
+
+type Bounds = (Int,Int) -- max x, max y
+
+type Pos = (Int,Int)
+
+toObjs :: Char -> MapObjects
+toObjs '#' = MOObstacle
+toObjs 'O' = MOExtraObstacle
+toObjs '^' = MOGuard GDNorth
+toObjs '>' = MOGuard GDEast
+toObjs 'v' = MOGuard GDSouth
+toObjs '<' = MOGuard GDWest
+toObjs _ = MOEmpty
+
+isMOGuard :: MapObjects -> Bool
+isMOGuard (MOGuard _) = True
+isMOGuard _ = False
+
+guardDirection :: MapObjects -> Maybe GuardDirection
+guardDirection (MOGuard x) = Just x
+guardDirection _ = Nothing
+
+parseInput :: Text -> AoCMap
+parseInput txt = AoCMap (xmax,ymax) objs
+  where
+    xxs = T.lines txt
+    xmax = T.length $ head xxs
+    ymax = length xxs
+    objs :: V.Vector MapObjects
+    objs = V.fromList $ concatMap (map toObjs . T.unpack) (reverse xxs)
+
+toIndex :: Pos -> Bounds -> Maybe Int
+toIndex (x,y) (xmax,ymax)
+  | x >= 0 && x < xmax && y >= 0 && y < ymax
+  = Just $ x + y*xmax
+toIndex _ _ = Nothing
+
+toPos :: Int -> Int -> Pos
+toPos i xmax = (i `mod` xmax, i `div` xmax)
+
+guardPath :: AoCMap -> [Pos]
+guardPath (AoCMap bounds@(xmax,_ymax) myMap) =
+  unfoldr step (initialPos myMap xmax,initialOri myMap)
+  where
+    step :: (Pos,GuardDirection) -> Maybe (Pos, (Pos,GuardDirection))
+    step (p,dir) = do
+      i <- toIndex (nextPos dir p) bounds
+      ahead <- myMap V.!? i
+      pure $ case ahead of
+        MOObstacle -> (p,(p,s dir))
+        _          -> (p,(nextPos dir p,dir))
+
+-- trace the trajectory of the Guard until it exits the map
+-- return the number of unique positions it occupied, including the starting
+-- one
+solveA :: Text -> Int
+solveA = (+1) . length . map NE.head . NE.group . sort . guardPath . parseInput
+
+nextPos :: GuardDirection -> Pos -> Pos
+nextPos GDNorth (x,y) = (x,y+1)
+nextPos GDEast  (x,y) = (x+1,y)
+nextPos GDSouth (x,y) = (x,y-1)
+nextPos GDWest  (x,y) = (x-1,y)
+
+initialPos :: V.Vector MapObjects -> Int -> Pos
+initialPos myMap xmax = (`toPos` xmax) . fromJust $ V.findIndex isMOGuard myMap
+
+initialOri :: V.Vector MapObjects -> GuardDirection
+initialOri myMap = fromJust $ do
+  guard <- V.find isMOGuard myMap
+  guardDirection guard
+
+type Trail = H.HashSet (Pos,GuardDirection)
+
+isGuardCycle :: AoCMap -> Pos -> Bool
+isGuardCycle (AoCMap bounds@(xmax,_ymax) myMap) newObs =
+  traceShow newObs $
+  or $ unfoldr step (initialPos myMap xmax
+                    ,initialOri myMap
+                    ,H.empty
+                    ,False)
+  where
+    step :: (Pos,GuardDirection,Trail,Bool)
+         -> Maybe (Bool, (Pos,GuardDirection,Trail,Bool))
+    step (p,dir,trail,end) = do
+      i <- toIndex (nextPos dir p) bounds
+      ahead <- myMap V.!? i
+      let isNewObs = nextPos dir p == newObs
+      let nextTrail = H.insert (p,dir) trail
+      case (ahead, isNewObs, (p,dir) `H.member` trail,end) of
+        (_,_,_,True)        -> Nothing
+        (_,_,True,_)        -> trace ">>>>>>>>>>>Cycle!<<<<<<<<<<<"
+                               $ Just (True,(p,dir,nextTrail,True))
+        (_,True,_,_)        -> Just (False,(p,s dir,nextTrail,False))
+        (MOObstacle,_,_,_)  -> Just (False,(p,s dir,nextTrail,False))
+        _                   -> Just (False,(nextPos dir p,dir,nextTrail,False))
+
+freePos :: AoCMap -> [Pos]
+freePos (AoCMap (xmax,_ymax) myMap) =
+  V.toList ((`toPos` xmax) <$> V.elemIndices MOEmpty myMap)
+
+solveB :: Text -> Int
+solveB input = length . filter id
+  $ parMap rpar (isGuardCycle aocmap) (freePos aocmap)
+  where
+    aocmap = parseInput input
+
+-- solveB :: Text -> IO Int
+-- solveB input = length . filter id
+--   <$> mapConcurrently (pure . isGuardCycle aocmap) (freePos aocmap)
+--   where
+--     aocmap = parseInput input
+
+inputEx :: Text
+inputEx = T.unlines
+  ["....#....."
+  ,".........#"
+  ,".........."
+  ,"..#......."
+  ,".......#.."
+  ,".........."
+  ,".#..^....."
+  ,"........#."
+  ,"#........."
+  ,"......#..."
+  ]
+
+main :: IO ()
+main = do
+  input <- T.readFile "inputs/day6.input"
+  putStrLn "Part 1"
+  print $ solveA input
+  putStrLn "Part 2"
+  print $ solveB input
+  --print =<< solveB input