Day fourteen

day-14-haskell/.gitignore

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+.stack-work/
+*~

day-14-haskell/Setup.hs

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+import Distribution.Simple
+main = defaultMain

day-14-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-14-haskell/day14-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:           day14-haskell
+version:        0.1.0.0
+homepage:       https://github.com/githubuser/day14-haskell#readme
+bug-reports:    https://github.com/githubuser/day14-haskell/issues
+author:         Author name here
+maintainer:     example@example.com
+copyright:      2024 Author name here
+license:        BSD-3-Clause
+build-type:     Simple
+
+source-repository head
+  type: git
+  location: https://github.com/githubuser/day14-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 day14-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
+    , day14-haskell
+  default-language: Haskell2010
+
+test-suite day14-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
+    , day14-haskell
+  default-language: Haskell2010

day-14-haskell/package.yaml

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+name:                day14-haskell
+version:             0.1.0.0
+github:              "githubuser/day14-haskell"
+license:             BSD-3-Clause
+author:              "Author name here"
+maintainer:          "example@example.com"
+copyright:           "2024 Author name here"
+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:
+  day14-haskell-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day14-haskell
+
+tests:
+  day14-haskell-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day14-haskell

day-14-haskell/src/Lib.hs

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+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE TupleSections #-}
+
+module Lib where
+
+import Control.Monad (join)
+import Data.Char
+import qualified Data.Map.Strict as Map
+import Data.Maybe (isJust)
+import Text.ParserCombinators.ReadP
+import Flow
+
+data Vec2 = Vec2 Integer Integer
+  deriving (Show, Eq, Ord)
+
+vAdd :: Vec2 -> Vec2 -> Vec2
+vAdd (Vec2 aX aY) (Vec2 bX bY) = Vec2 (aX + bX) (aY + bY)
+
+data Robot = Robot { rPos :: Vec2, rVel :: Vec2 }
+  deriving (Show)
+type BotCountMap = Map.Map Vec2 Int
+
+task1 :: String -> IO Int
+task1 input =
+  let area = Vec2 101 103
+      robots = parseFile input
+      simulated = simulate area 100 robots
+      sorted = sortIntoQuadrants area simulated
+  in return $ product $ map length sorted
+
+task2 :: String -> IO Int
+task2 input =
+  let area = Vec2 101 103
+      robots = parseFile input
+  in step area 1 robots
+  where
+    step :: Vec2 -> Int -> [Robot] -> IO Int
+    step area counter robots =
+      let simulated = simulate area 1 robots
+      in if checkForImage simulated
+         then do
+           putStrLn $ showWorld area simulated
+           return counter
+         else step area (counter+1) simulated
+
+    checkForImage :: [Robot] -> Bool
+    checkForImage robots =
+      let botMap = botsAtPos robots
+      in Map.keys botMap |> filter (hasAdjacent botMap) |> length |> (<) (Map.size botMap `div` 2)
+
+    hasAdjacent :: BotCountMap -> Vec2 -> Bool
+    hasAdjacent botMap pos =
+      map (vAdd pos) [Vec2 (-1) 0, Vec2 0 (-1), Vec2 1 0, Vec2 0 1] |> any (\p -> Map.member p botMap)
+
+showWorld :: Vec2 -> [Robot] -> String
+showWorld (Vec2 aX aY) robots = 
+  let botMap = botsAtPos robots
+  in [0..(aY - 1)] |> map (line botMap) |> join
+    where
+      line :: BotCountMap -> Integer -> String
+      line botMap y = join [charFor (Vec2 x y) | x <- [0..(aX-1)]] ++ "\n"
+        where
+          charFor :: Vec2 -> String
+          charFor pos = case botMap Map.!? pos of
+            Nothing -> "."
+            Just num -> show num
+
+botsAtPos :: [Robot] -> BotCountMap
+botsAtPos robots = map ((,1) . rPos) robots |> Map.fromListWith (+)
+
+sortIntoQuadrants :: Vec2 -> [Robot] -> [[Robot]]
+sortIntoQuadrants (Vec2 aX aY) robots = map (\r -> (quadrant r, [r])) robots |> filter (\(q, _) -> isJust q) |> Map.fromListWith (++) |> Map.elems
+  where
+    quadrant :: Robot -> Maybe Int
+    quadrant Robot { rPos = (Vec2 pX pY) } = do
+      xOffset <- qOffset aX pX
+      yOffset <- fmap ((*) 2) $ qOffset aY pY
+      return $ xOffset + yOffset
+
+    qOffset :: Integer -> Integer -> Maybe Int
+    qOffset a p = case a `divMod` 2 of
+      (half, 0) -> if p < half then Just 0 else Just 1
+      (half, _) -> oddOffset
+        where
+          oddOffset
+            | p < half = Just 0
+            | p > half = Just 1
+            | otherwise = Nothing
+
+simulate :: Vec2 -> Integer -> [Robot] -> [Robot]
+simulate (Vec2 aX aY) seconds robots = map simulateRobot robots
+  where
+    simulateRobot :: Robot -> Robot
+    simulateRobot Robot { rPos = (Vec2 pX pY), rVel = vel@(Vec2 vX vY) } = 
+      let newX = simulateCoord aX vX pX
+          newY = simulateCoord aY vY pY
+      in Robot { rPos = (Vec2 newX newY), rVel = vel }
+    simulateCoord :: Integer -> Integer -> Integer -> Integer
+    simulateCoord a v p = (p + v * seconds) `mod` a
+
+parseFile :: String -> [Robot]
+parseFile input = case readP_to_S parse input of
+  [] -> error $ "Failed to parse input: " ++ input
+  ((rs,_):_) -> rs
+  where
+    parse :: ReadP [Robot]
+    parse = do
+      robots <- parseRobots
+      _ <- eof
+      return robots
+
+parseRobots :: ReadP [Robot]
+parseRobots = many1 parseRobot
+
+parseRobot :: ReadP Robot
+parseRobot = do
+  _ <- string "p="
+  pos <- parseVec
+  _ <- string " v="
+  vel <- parseVec
+  _ <- munch1 isNewLine
+  return $ Robot { rPos = pos, rVel = vel }
+
+parseVec :: ReadP Vec2
+parseVec = do
+  x <- parseNumber
+  _ <- string ","
+  y <- parseNumber
+  return $ Vec2 x y
+
+parseNumber :: ReadP Integer
+parseNumber = do
+  sign <- option ' ' $ satisfy ((==) '-')
+  digits <- munch1 isNumber
+  return $ read $ sign : digits
+
+isNewLine :: Char -> Bool
+isNewLine = (==) '\n'

day-14-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-14-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-14-haskell/test/Spec.hs

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