Day sixteen part one

day-16-haskell/.gitignore

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+.stack-work/
+*~

day-16-haskell/Setup.hs

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+import Distribution.Simple
+main = defaultMain

day-16-haskell/app/Main.hs

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+module Main (main) where
+
+import System.Environment.Blank ( getArgs )
+import Lib (task1, task2)
+
+main :: IO ()
+main = do
+  args <- getArgs
+  case args of
+    ["1", file] -> do
+      input <- readFile file
+      result <- task1 input
+      print result
+    ["2", file] -> do
+      input <- readFile file
+      result <- task2 input
+      print result
+    _ -> error "Usage: <1|2> <input file>"

day-16-haskell/day16-haskell.cabal

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+cabal-version: 2.2
+
+-- This file has been generated from package.yaml by hpack version 0.37.0.
+--
+-- see: https://github.com/sol/hpack
+
+name:           day16-haskell
+version:        0.1.0.0
+homepage:       https://github.com/Siphalor/day16-haskell#readme
+bug-reports:    https://github.com/Siphalor/day16-haskell/issues
+author:         Siphalor
+maintainer:     info@siphalor.de
+copyright:      Siphalor
+license:        BSD-3-Clause
+build-type:     Simple
+
+source-repository head
+  type: git
+  location: https://github.com/Siphalor/day16-haskell
+
+library
+  exposed-modules:
+      Lib
+  hs-source-dirs:
+      src
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
+  build-depends:
+      base >=4.7 && <5
+    , containers
+    , flow
+  default-language: Haskell2010
+
+executable day16-haskell-exe
+  main-is: Main.hs
+  hs-source-dirs:
+      app
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , day16-haskell
+  default-language: Haskell2010
+
+test-suite day16-haskell-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  hs-source-dirs:
+      test
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , day16-haskell
+  default-language: Haskell2010

day-16-haskell/package.yaml

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+name:                day16-haskell
+version:             0.1.0.0
+github:              "Siphalor/day16-haskell"
+license:             BSD-3-Clause
+author:              "Siphalor"
+maintainer:          "info@siphalor.de"
+copyright:           "Siphalor"
+spec-version:        0.36.0
+
+dependencies:
+- base >= 4.7 && < 5
+
+ghc-options:
+- -Wall
+- -Wcompat
+- -Widentities
+- -Wincomplete-record-updates
+- -Wincomplete-uni-patterns
+- -Wmissing-home-modules
+- -Wpartial-fields
+- -Wredundant-constraints
+
+library:
+  source-dirs: src
+  dependencies:
+  - flow
+  - containers
+
+executables:
+  day16-haskell-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day16-haskell
+
+tests:
+  day16-haskell-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day16-haskell

day-16-haskell/src/Lib.hs

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+{-# LANGUAGE NamedFieldPuns #-}
+
+module Lib where
+
+import Control.Monad (join)
+import Flow
+import qualified Data.Map.Strict as Map
+import Data.Maybe (listToMaybe, maybeToList)
+import qualified Data.Set as Set
+import Text.ParserCombinators.ReadP
+
+type IntType = Int
+
+data Vec2 = Vec2 IntType IntType
+  deriving (Eq, Ord, Show)
+vAdd :: Vec2 -> Vec2 -> Vec2
+vAdd (Vec2 aX aY) (Vec2 bX bY) = Vec2 (aX+bX) (aY+bY)
+
+data Direction = North | East | South | West
+  deriving (Eq, Ord, Show)
+dOpposite :: Direction -> Direction
+dOpposite North = South
+dOpposite East = West
+dOpposite South = North
+dOpposite West = East
+dVec :: Direction -> Vec2
+dVec North = Vec2 0 (-1)
+dVec East = Vec2 1 0
+dVec South = Vec2 0 1
+dVec West = Vec2 (-1) 0
+
+data Tile = Path | Start | End | Wall
+  deriving (Eq, Ord, Show)
+
+type WorldMap = Map.Map Vec2 Tile
+
+data Edge = Edge { eDirFrom :: Direction, eFrom :: Vec2, eDirTo :: Direction, eTo :: Vec2, ePrice :: Int }
+  deriving (Show)
+
+type WorldGraphEdges = Map.Map Vec2 [Edge]
+data WorldGraph = WorldGraph { wStart :: Vec2, wEnd :: Vec2, wEdges :: WorldGraphEdges }
+  deriving (Show)
+
+task1 :: String -> IO IntType
+task1 input =
+  let worldMap = parseFile input
+      rawGraph = mapToGraph worldMap
+  in do
+    --rawGraph |> wEdges |> Map.elems |> join |> showEdgesSimple |> putStrLn
+    worldGraph <- simplifyGraph rawGraph
+    worldGraph |> wEdges |> Map.elems |> join |> showEdgesSimple |> putStrLn
+    --return $ expectJust "No path found" $ findBestPath worldGraph [(wStart worldGraph, East)]
+    bestPath <- dijkstra worldGraph Map.empty (Map.singleton (wStart worldGraph, East) 0)
+    return $ expectJust "No path found" $ bestPath
+
+task2 :: String -> IO IntType
+task2 _ = return 2
+
+showEdgesSimple :: [Edge] -> String
+showEdgesSimple [] = ""
+showEdgesSimple (edge:edges) = (show $ eFrom edge) ++ " -> " ++ (show $ eTo edge) ++ ": " ++ (show $ ePrice edge) ++ "\n" ++ (showEdgesSimple edges)
+
+dijkstra :: WorldGraph -> Map.Map (Vec2, Direction) Int -> Map.Map (Vec2, Direction) Int -> IO (Maybe Int)
+dijkstra world@WorldGraph { wEdges, wEnd } done unvisited
+  | null unvisited =
+    [North, East, South, West] |> map (\d -> done Map.!? (wEnd, d) |> maybeToList) |> join |> minimum |> pure |> return
+  | otherwise =
+    let ((pos, dir), cost) = findNext
+        outgoing = Map.findWithDefault [] pos wEdges
+        unvisitedOutgoing = outgoing |> filter (\Edge { eTo, eDirTo } -> Map.notMember (eTo, eDirTo) done)
+        unvisitedOutgoingWithPrice = unvisitedOutgoing |> map (\e@Edge { eDirFrom, ePrice } -> (e, if dir == dOpposite eDirFrom then cost + ePrice else cost + ePrice + 1000)) :: [(Edge, IntType)]
+        unvisitedWithoutCurrent = Map.delete (pos, dir) unvisited
+        nextUnvisited = foldr (\(Edge { eTo, eDirTo }, price) -> Map.alter (pure . maybe price (min price)) (eTo, eDirTo)) unvisitedWithoutCurrent unvisitedOutgoingWithPrice
+        nextDone = Map.insert (pos, dir) cost done
+    in do
+      -- putStrLn $ "Processing " ++ (show pos) ++ "/" ++ (show dir)
+      -- print nextUnvisited
+      dijkstra world nextDone nextUnvisited
+  where
+    findNext :: ((Vec2, Direction), Int)
+    findNext =
+      let options = unvisited |> Map.assocs
+      in foldr (\a@(_,aC) b@(_,bC) -> if aC < bC then a else b) (head options) (drop 1 options)
+
+findBestPath :: WorldGraph -> [(Vec2, Direction)] -> Maybe Int
+findBestPath _ [] = error "Must call findBestPath with an initial position"
+findBestPath world@WorldGraph { wEdges, wEnd } ((lastPos, lastDir):path) =
+  let edgeOptions = wEdges Map.!? lastPos |> expectJust ("Position is missing in map " ++ show lastPos) |> filter (\Edge{eTo=optTo} -> not $ listContains optTo $ map (\(p,_) -> p) path)
+  in case edgeOptions |> map (maybeToList . exploreOption) |> join of
+    [] -> Nothing
+    prices -> return $ minimum prices
+  where
+    exploreOption :: Edge -> Maybe Int
+    exploreOption edge@Edge{ePrice, eDirFrom, eTo, eDirTo}
+      | eTo == wEnd = Just hopPrize
+      | otherwise = findBestPath world ((eTo, eDirTo):(lastPos, lastDir):path) |> fmap (\pr -> pr + hopPrize)
+      where
+        hopPrize :: Int
+        hopPrize = if eDirFrom == dOpposite lastDir then ePrice else ePrice + 1000
+
+mapToGraph :: WorldMap -> WorldGraph
+mapToGraph worldMap =
+  let start = Map.assocs worldMap |> filter (\(_, t) -> t == Start) |> listToMaybe |> expectJust "No start found" |> entryKey
+      end = Map.assocs worldMap |> filter (\(_, t) -> t == End) |> listToMaybe |> expectJust "No end found" |> entryKey
+      pathMap = worldMap |> Map.filter ((/=) Wall)
+      edges = pathMap |> Map.keys |> map edgesFromPos |> join
+      edgesByFrom = map (\e -> (eFrom e, [e])) edges |> Map.fromListWith (++)
+  in WorldGraph { wStart = start, wEnd = end, wEdges = edgesByFrom }
+
+  where
+    edgesFromPos :: Vec2 -> [Edge]
+    edgesFromPos pos =
+      [North, East, South, West]
+      |> map (\dir -> dVec dir |> vAdd pos |> \t -> if validTarget $ worldMap Map.!? t then [Edge { eDirTo = dir, eTo = t, eDirFrom = dOpposite dir, eFrom = pos, ePrice = 1 }] else [])
+      |> join
+
+    validTarget :: Maybe Tile -> Bool
+    validTarget (Just Wall) = False
+    validTarget (Just _) = True
+    validTarget _ = False
+
+simplifyGraph :: WorldGraph -> IO WorldGraph
+simplifyGraph world@WorldGraph { wStart, wEnd, wEdges } =
+  case Map.assocs wEdges |> filter (\(p, edges) -> p /= wStart && p /= wEnd && length edges <= 2) of
+    [] -> return world
+    ((pos, []):_) -> simplifyGraph WorldGraph { wStart, wEnd, wEdges = Map.delete pos wEdges }
+    ((_, [e]):_) -> do
+      --putStrLn $ "Removing " ++ (show e)
+      simplifyGraph WorldGraph { wStart, wEnd, wEdges = removeEdge e wEdges }
+    ((_, [e1, e2]):_) ->
+      let newEdges = wEdges |> combineEdges e1 e2
+      in do
+        --putStrLn $ "Combining " ++ (show e1) ++ " : " ++ (show e2)
+        simplifyGraph WorldGraph { wStart, wEnd, wEdges = newEdges }
+    _ -> error "Ureachable in simplifyGraph"
+  where
+    combineEdges :: Edge -> Edge -> WorldGraphEdges -> WorldGraphEdges
+    combineEdges e1@Edge { eDirFrom = eDirFrom1, eTo = eTo1, eDirTo = eDirTo1, ePrice = ePrice1 } e2@Edge { eDirFrom = eDirFrom2, eTo = eTo2, eDirTo = eDirTo2, ePrice = ePrice2 } edges =
+      let combinedPrice = ePrice1 + ePrice2 + if eDirFrom1 == dOpposite eDirFrom2 then 0 else 1000
+      in edges |> removeEdge e1 |> removeEdge e2
+          |> Map.adjust (\es -> Edge { eFrom = eTo1, eDirFrom = eDirTo1, eTo = eTo2, eDirTo = eDirTo2, ePrice = combinedPrice }:es) eTo1
+          |> Map.adjust (\es -> Edge { eFrom = eTo2, eDirFrom = eDirTo2, eTo = eTo1, eDirTo = eDirTo1, ePrice = combinedPrice }:es) eTo2
+    
+    removeEdge :: Edge -> WorldGraphEdges -> WorldGraphEdges
+    removeEdge Edge { eFrom, eTo } edgesMap =
+      edgesMap
+      |> Map.adjust (\edges -> edges |> filter (not . (isEdgeTo eTo))) eFrom
+      |> Map.adjust (\edges -> edges |> filter (not . (isEdgeTo eFrom))) eTo
+ 
+    isEdgeTo :: Vec2 -> Edge -> Bool
+    isEdgeTo testTo Edge { eTo } = testTo == eTo
+
+parseFile :: String -> WorldMap
+parseFile input =
+  case readP_to_S parse input of
+    [] -> error "Failed to parse"
+    ((v,_):_) -> v
+
+  where
+    parse :: ReadP WorldMap
+    parse = do
+      worldMap <- parseWorld
+      _ <- eof
+      return worldMap
+
+parseWorld :: ReadP WorldMap
+parseWorld = do
+  ls <- many1 parseLine
+  zip [0..] ls |> map (\(y, line) -> zip [0..] line |> map (\(x, c) -> (Vec2 x y, toTile c))) |> join |> Map.fromList |> return
+
+  where
+    parseLine :: ReadP String
+    parseLine = do
+      content <- munch1 (not . isNewLine)
+      _ <- char '\n'
+      return content
+    
+    toTile :: Char -> Tile
+    toTile '.' = Path
+    toTile 'S' = Start
+    toTile 'E' = End
+    toTile '#' = Wall
+    toTile c = error $ "Unknown tile: " ++ [c]
+
+isNewLine :: Char -> Bool
+isNewLine = (==) '\n'
+
+listContains :: Eq a => a -> [a] -> Bool
+listContains _ [] = False
+listContains a (e:es) = if a == e then True else listContains a es
+
+nothingIfEmpty :: Foldable t => t a -> Maybe (t a)
+nothingIfEmpty values
+  | null values = Nothing
+  | otherwise = Just values
+
+entryKey :: (a,b) -> a
+entryKey (k,_) = k
+entryValue :: (a,b) -> b
+entryValue (_,v) = v
+
+expectJust :: String -> Maybe a -> a
+expectJust message Nothing = error message
+expectJust _ (Just value) = value
+

day-16-haskell/stack.yaml

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+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# A 'specific' Stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# snapshot: lts-22.28
+# snapshot: nightly-2024-07-05
+# snapshot: ghc-9.6.6
+#
+# The location of a snapshot can be provided as a file or url. Stack assumes
+# a snapshot provided as a file might change, whereas a url resource does not.
+#
+# snapshot: ./custom-snapshot.yaml
+# snapshot: https://example.com/snapshots/2024-01-01.yaml
+snapshot:
+  url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/23/0.yaml
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+#   subdirs:
+#   - auto-update
+#   - wai
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the snapshot.
+# These entries can reference officially published versions as well as
+# forks / in-progress versions pinned to a git hash. For example:
+#
+# extra-deps:
+# - acme-missiles-0.3
+# - git: https://github.com/commercialhaskell/stack.git
+#   commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#
+# extra-deps: []
+
+# Override default flag values for project packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of Stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=3.1"
+#
+# Override the architecture used by Stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by Stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

day-16-haskell/stack.yaml.lock

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+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 9444fadfa30b67a93080254d53872478c087592ad64443e47c546cdcd13149ae
+    size: 678857
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/23/0.yaml
+  original:
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/23/0.yaml

day-16-haskell/test/Spec.hs

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+main :: IO ()
+main = putStrLn "Test suite not yet implemented"