Day eightteen

day-18-haskell/.gitignore

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+.stack-work/
+*~

day-18-haskell/Setup.hs

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+import Distribution.Simple
+main = defaultMain

day-18-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-18-haskell/day18-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:           day18-haskell
+version:        0.1.0.0
+homepage:       https://github.com/Siphalor/day18-haskell#readme
+bug-reports:    https://github.com/Siphalor/day18-haskell/issues
+author:         Siphalor
+maintainer:     info@siphalor.de
+copyright:      Siphalor
+license:        BSD-3-Clause
+license-file:   LICENSE
+build-type:     Simple
+
+source-repository head
+  type: git
+  location: https://github.com/Siphalor/day18-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 day18-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
+    , day18-haskell
+  default-language: Haskell2010
+
+test-suite day18-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
+    , day18-haskell
+  default-language: Haskell2010

day-18-haskell/package.yaml

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+name:                day18-haskell
+version:             0.1.0.0
+github:              "Siphalor/day18-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:
+  day18-haskell-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day18-haskell
+
+tests:
+  day18-haskell-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day18-haskell

day-18-haskell/src/Lib.hs

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+module Lib where
+
+import Data.Char (isNumber)
+import qualified Data.Map.Strict as Map
+import Data.Maybe (isJust)
+import qualified Data.Set as Set
+import Flow
+import Text.ParserCombinators.ReadP
+
+data Direction = DUp | DRight | DDown | DLeft
+  deriving (Eq, Ord, Show)
+dVec :: Direction -> Vec2
+dVec DUp = Vec2 0 (-1)
+dVec DRight = Vec2 1 0
+dVec DDown = Vec2 0 1
+dVec DLeft = Vec2 (-1) 0
+dClock :: Direction -> Direction
+dClock DUp = DRight
+dClock DRight = DDown
+dClock DDown = DLeft
+dClock DLeft = DUp
+dCClock :: Direction -> Direction
+dCClock DUp = DLeft
+dCClock DRight = DUp
+dCClock DDown = DRight
+dCClock DLeft = DDown
+allDirections :: [Direction]
+allDirections = [DUp, DRight, DDown, DLeft]
+
+data Vec2 = Vec2 Int Int
+  deriving (Eq, Ord, Show)
+vAdd :: Vec2 -> Vec2 -> Vec2
+vAdd (Vec2 aX aY) (Vec2 bX bY) = Vec2 (aX + bX) (aY + bY)
+
+data Tile = Safe | Corrupted
+  deriving (Eq, Show)
+
+type World = Map.Map Vec2 Tile
+
+task1 :: String -> IO Int
+task1 input =
+  let falling = readInput input
+      mapWidth = 70
+      world = [(Vec2 x y, Safe) | x <- [0..mapWidth], y <- [0..mapWidth]] |> Map.fromList
+      corruptedWorld = falling |> take 1024 |> foldr (\p -> Map.insert p Corrupted) world
+  in do
+    return $ expectJust "No path found" $ dijkstra corruptedWorld Set.empty (Map.singleton (Vec2 0 0) 0)
+
+task2 :: String -> IO Vec2
+task2 input =
+  let falling = readInput input
+      mapWidth = 70
+      world = [(Vec2 x y, Safe) | x <- [0..mapWidth], y <- [0..mapWidth]] |> Map.fromList
+      corruptedWorlds = foldEmitting (\v (lastWorld, _) -> (Map.insert v Corrupted lastWorld, v)) (world, Vec2 0 0) falling
+      exit = Map.keys world |> maximum
+      (blockedWorld, blockingV) = corruptedWorlds |> dropWhile (\(w, _) -> wallRunner w exit Set.empty (Vec2 0 0) DRight) |> head
+  in do
+    return blockingV
+  
+  where
+    foldEmitting :: (a -> b -> b) -> b -> [a] -> [b]
+    foldEmitting _ current [] = [current]
+    foldEmitting folder current (value:values) =
+      let next = folder value current
+      in current : foldEmitting folder next values
+
+dijkstra :: World -> Set.Set Vec2 -> Map.Map Vec2 Int -> Maybe Int
+dijkstra world done unvisited
+  | null unvisited = Nothing
+  | otherwise =
+    let exit = Map.keys world |> maximum
+        options = Map.assocs unvisited
+        (curV, curP) = options |> foldr (\(nV, nP) (bestV, bestP) -> if nP < bestP then (nV, nP) else (bestV, bestP)) (head options)
+        unfinishedOutgoing = allDirections |> map dVec |> map (vAdd curV) |> filter (\v -> Set.notMember v done) |> filter (\v -> world Map.!? v == Just Safe)
+        unvisitedWithoutCurrent = unvisited |> Map.delete curV
+        nextUnvisited = foldr (Map.alter (pure . maybe (curP+1) (min (curP+1)))) unvisitedWithoutCurrent unfinishedOutgoing
+    in if curV == exit
+      then Just curP
+      else dijkstra world (Set.insert curV done) nextUnvisited
+
+wallRunner :: World -> Vec2 -> Set.Set (Vec2, Direction) -> Vec2 -> Direction -> Bool
+wallRunner world end visited last lastDir =
+  let options = [dCClock lastDir, lastDir, dClock lastDir, dClock $ dClock lastDir] |> map (\d -> (d, vAdd last $ dVec d))
+      (nextDir, next) = options |> filter (\(_,v) -> canEnter v) |> head
+  in action next nextDir
+  where
+    canEnter :: Vec2 -> Bool
+    canEnter pos =
+      case world Map.!? pos of
+        Just Safe -> True
+        _ -> False
+
+    action :: Vec2 -> Direction -> Bool
+    action cur curDir
+      | Set.member (cur, curDir) visited = False
+      | cur == end = True
+      | otherwise = wallRunner world end (Set.insert (cur, curDir) visited) cur curDir
+
+readInput :: String -> [Vec2]
+readInput input =
+  case readP_to_S parse input of
+    [] -> error "Failed to parse input"
+    ((vecs,_):_) -> vecs
+  where
+    parse :: ReadP [Vec2]
+    parse = do
+      vecs <- sepBy1 parseVec (char '\n')
+      _ <- munch ((==) '\n')
+      _ <- eof
+      return vecs
+
+parseVec :: ReadP Vec2
+parseVec = do
+  x <- parseInt
+  _ <- char ','
+  y <- parseInt
+  return $ Vec2 x y
+
+parseInt :: ReadP Int
+parseInt = do
+  digits <- munch1 isNumber
+  return $ read digits
+
+expectJust :: String -> Maybe a -> a
+expectJust message Nothing = error message
+expectJust _ (Just value) = value
+

day-18-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-18-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-18-haskell/test/Spec.hs

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