7 files changed, 326 insertions, 0 deletions
diff --git a/2021/day23/Setup.hs b/2021/day23/Setup.hs
new file mode 100644
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--- /dev/null
+++ b/2021/day23/Setup.hs
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+import Distribution.Simple
+main = defaultMain
diff --git a/2021/day23/app/Main.hs b/2021/day23/app/Main.hs
new file mode 100644
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--- /dev/null
+++ b/2021/day23/app/Main.hs
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+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TupleSections #-}
+module Main where
+
+import Algorithm.Search (dijkstraAssoc)
+import qualified Data.Text as T
+import Data.Maybe (listToMaybe, catMaybes)
+import Data.List (intercalate, transpose)
+import Data.Char (isLetter)
+import Data.Map (Map)
+import qualified Data.Map as M
+import Data.Set (Set)
+import qualified Data.Set as S
+
+data Species = Am | Br | Co | De deriving (Show, Eq, Ord)
+type Coord = (Int, Int)
+type Board = Map Coord Species
+
+toSpecies :: Char -> Species
+toSpecies 'A' = Am
+toSpecies 'B' = Br
+toSpecies 'C' = Co
+toSpecies 'D' = De
+
+cost :: Species -> Int
+cost Am = 1
+cost Br = 10
+cost Co = 100
+cost De = 1000
+
+roomX :: Species -> Int
+roomX Am = 1
+roomX Br = 3
+roomX Co = 5
+roomX De = 7
+
+isRoomX :: Int -> Bool
+isRoomX 1 = True
+isRoomX 3 = True
+isRoomX 5 = True
+isRoomX 7 = True
+isRoomX _ = False
+
+lowerBound = (-1)
+upperBound = 9
+lowestY = 4
+
+inBounds :: Coord -> Bool
+inBounds (x, _) = x >= lowerBound && x <= upperBound
+
+parseFile :: String -> Board
+parseFile s = foldl insertRoom M.empty rooms
+  where letters = transpose $ map (map toSpecies . filter isLetter . T.unpack) $ T.splitOn "\n" (T.pack s)
+        rooms = zip [Am, Br, Co, De] letters
+        insertRoom m (s, cs) = (M.fromList [((roomX s, y), c) | (y, c) <- zip [1..] cs]) `M.union` m
+
+topOfRoom :: Board -> Int -> Maybe Coord
+topOfRoom b x = listToMaybe $ filter (`M.member` b) [(x, y) | y <- [1..lowestY]]
+
+availableHallwaySpaces :: Board -> Int -> [Coord]
+availableHallwaySpaces b sx = (exploreWith (+ 1) sx) ++ (exploreWith (+ (-1)) (sx - 1))
+  where exploreWith f x | isRoomX x = exploreWith f (f x)
+                        | not (inBounds (x, 0)) = []
+                        | (x, 0) `M.member` b = []
+                        | otherwise = (x, 0) : exploreWith f (f x)
+
+pathToRoom :: Coord -> Species -> [Coord]
+pathToRoom (sx, _) es | sx <= ex  = map (, 0) [sx + 1..ex]
+                      | otherwise = map (, 0) [ex..sx - 1]
+  where ex = roomX es
+
+pathClear :: Board -> [Coord] -> Bool
+pathClear b path = all (`M.notMember` b) path
+
+toTopOfRoom :: Int -> Int
+toTopOfRoom x = x - 1
+
+movingFromRoom :: Board -> Species -> [(Board, Int)]
+movingFromRoom b s = case topOfRoom b (roomX s) of
+                       Just (x, y) -> let withoutTop = (x, y) `M.delete` b
+                                          extraCost = toTopOfRoom y
+                                          Just movingOut = (x, y) `M.lookup` b
+                                          in [(M.insert c movingOut withoutTop, (abs ((fst c) - x) + 1 + extraCost) * cost movingOut) | c <- availableHallwaySpaces b x]
+                       Nothing -> []
+
+roomPositions = [1..lowestY]
+
+movingIntoRoom :: Board -> [(Board, Int)]
+movingIntoRoom b = concatMap attemptMoveToRoom [((c, 0), (c, 0) `M.lookup` b) | c <- [lowerBound..upperBound]]
+  where attemptMoveToRoom (_, Nothing)  = []
+        attemptMoveToRoom (c, Just s) | not clear = []
+                                      | otherwise = [(b', (length p + 1 + extraCost) * (cost s))]
+          where p = pathToRoom c s
+                clear = pathClear b p && hasSpace && isCorrect
+                occupants = catMaybes [(roomX s, y) `M.lookup` b | y <- roomPositions]
+                hasSpace = length occupants < lowestY
+                isCorrect = all (== s) occupants
+                y' = lowestY - (length occupants)
+                extraCost = toTopOfRoom y'
+                c' = (roomX s, y')
+                b' = M.insert c' s $ M.delete c b
+
+species = [Am, Br, Co, De]
+
+nextMoves :: Board -> [(Board, Int)]
+nextMoves b = (concatMap (movingFromRoom b) species) ++ movingIntoRoom b
+
+isFinished :: Board -> Bool
+isFinished b = all id [(M.lookup (roomX s, rp) b) == Just s | s <- species, rp <- roomPositions]
+
+solve :: Board -> Maybe (Int, [Board])
+solve = dijkstraAssoc nextMoves isFinished
+
+printBoard :: Board -> String
+printBoard b = intercalate "\n" [printLine l | l <- [0..lowestY]]
+  where printLine l = [toChar ((x, l) `M.lookup` b) | x <- [lowerBound..upperBound]]
+        toChar Nothing = ' '
+        toChar (Just Am) = 'A'
+        toChar (Just Br) = 'B'
+        toChar (Just Co) = 'C'
+        toChar (Just De) = 'D'
+
+printNexts :: [(Board, Int)] -> IO [()]
+printNexts = sequence . map printNext
+
+printNext :: (Board, Int) -> IO ()
+printNext (b, c) = do
+  putStrLn $ printBoard b
+  print c
+
+main :: IO ()
+main = do
+  input <- readFile "./input"
+  let parsed = parseFile input
+  let Just (cost, path) = solve parsed
+  putStrLn $ intercalate "\n---\n" $ map printBoard path
+  print path
+  print cost
diff --git a/2021/day23/day23.cabal b/2021/day23/day23.cabal
new file mode 100644
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--- /dev/null
+++ b/2021/day23/day23.cabal
@@ -0,0 +1,52 @@
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.34.5.
+--
+-- see: https://github.com/sol/hpack
+
+name:           day23
+version:        0.1.0.0
+description:    Please see the README on GitHub at <https://github.com/githubuser/day23#readme>
+homepage:       https://github.com/githubuser/day23#readme
+bug-reports:    https://github.com/githubuser/day23/issues
+author:         Author name here
+maintainer:     example@example.com
+copyright:      2021 Author name here
+license:        BSD3
+build-type:     Simple
+extra-source-files:
+    README.md
+    ChangeLog.md
+
+source-repository head
+  type: git
+  location: https://github.com/githubuser/day23
+
+library
+  exposed-modules:
+      Lib
+  other-modules:
+      Paths_day23
+  hs-source-dirs:
+      src
+  build-depends:
+      base >=4.7 && <5
+    , containers
+    , search-algorithms
+    , text
+  default-language: Haskell2010
+
+executable day23-exe
+  main-is: Main.hs
+  other-modules:
+      Paths_day23
+  hs-source-dirs:
+      app
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , containers
+    , day23
+    , search-algorithms
+    , text
+  default-language: Haskell2010
diff --git a/2021/day23/package.yaml b/2021/day23/package.yaml
new file mode 100644
index 0000000..a41ad1f
--- /dev/null
+++ b/2021/day23/package.yaml
@@ -0,0 +1,40 @@
+name:                day23
+version:             0.1.0.0
+github:              "githubuser/day23"
+license:             BSD3
+author:              "Author name here"
+maintainer:          "example@example.com"
+copyright:           "2021 Author name here"
+
+extra-source-files:
+- README.md
+- ChangeLog.md
+
+# Metadata used when publishing your package
+# synopsis:            Short description of your package
+# category:            Web
+
+# To avoid duplicated efforts in documentation and dealing with the
+# complications of embedding Haddock markup inside cabal files, it is
+# common to point users to the README.md file.
+description:         Please see the README on GitHub at <https://github.com/githubuser/day23#readme>
+
+dependencies:
+- base >= 4.7 && < 5
+- containers
+- text
+- search-algorithms
+
+library:
+  source-dirs: src
+
+executables:
+  day23-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day23
diff --git a/2021/day23/src/Lib.hs b/2021/day23/src/Lib.hs
new file mode 100644
index 0000000..d36ff27
--- /dev/null
+++ b/2021/day23/src/Lib.hs
@@ -0,0 +1,6 @@
+module Lib
+    ( someFunc
+    ) where
+
+someFunc :: IO ()
+someFunc = putStrLn "someFunc"
diff --git a/2021/day23/stack.yaml b/2021/day23/stack.yaml
new file mode 100644
index 0000000..920ab59
--- /dev/null
+++ b/2021/day23/stack.yaml
@@ -0,0 +1,68 @@
+# 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/
+
+# Resolver to choose 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:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+#
+# 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.
+#
+# resolver: ./custom-snapshot.yaml
+# resolver: https://example.com/snapshots/2018-01-01.yaml
+resolver:
+  url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/20.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 resolver.
+# 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:
+  - search-algorithms-0.3.2
+
+# Override default flag values for local 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: ">=2.7"
+#
+# 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
diff --git a/2021/day23/stack.yaml.lock b/2021/day23/stack.yaml.lock
new file mode 100644
index 0000000..1f94557
--- /dev/null
+++ b/2021/day23/stack.yaml.lock
@@ -0,0 +1,20 @@
+# 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:
+- completed:
+    hackage: search-algorithms-0.3.2@sha256:9d224b9c6b5875598e6fc91497a178f3ca6e45768c637d07d4f874e6211a331b,2203
+    pantry-tree:
+      size: 557
+      sha256: 43e9d4344d57a3bad78f67d085156531e0a9b38a14dce9f5137940561fdb3582
+  original:
+    hackage: search-algorithms-0.3.2
+snapshots:
+- completed:
+    size: 586106
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/20.yaml
+    sha256: 8699812d2b2c1f83d6ad1261de9cf628ed36a1cfc14f19d67188e005e7a3a39d
+  original:
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/20.yaml