Day thirteen

day-13-haskell/.gitignore

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+.stack-work/
+*~

day-13-haskell/Setup.hs

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+import Distribution.Simple
+main = defaultMain

day-13-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-13-haskell/day13-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:           day13-haskell
+version:        0.1.0.0
+homepage:       https://github.com/githubuser/day13-haskell#readme
+bug-reports:    https://github.com/githubuser/day13-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/day13-haskell
+
+library
+  exposed-modules:
+      Lib
+  hs-source-dirs:
+      src
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
+  build-depends:
+      base >=4.7 && <5
+    , flow
+  default-language: Haskell2010
+
+executable day13-haskell-exe
+  main-is: Main.hs
+  hs-source-dirs:
+      app
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , day13-haskell
+  default-language: Haskell2010
+
+test-suite day13-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-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , day13-haskell
+  default-language: Haskell2010

day-13-haskell/package.yaml

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+name:                day13-haskell
+version:             0.1.0.0
+github:              "githubuser/day13-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-export-lists
+- -Wmissing-home-modules
+- -Wpartial-fields
+- -Wredundant-constraints
+
+library:
+  source-dirs: src
+  dependencies:
+  - flow
+
+executables:
+  day13-haskell-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day13-haskell
+
+tests:
+  day13-haskell-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - day13-haskell

day-13-haskell/src/Lib.hs

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+{-# LANGUAGE NamedFieldPuns #-}
+
+module Lib where
+
+import Data.Char
+import Data.Maybe (maybeToList)
+import Data.Ratio
+import Text.ParserCombinators.ReadP
+import Flow
+
+type IntType = Integer
+data Vec2 = Vec2 IntType IntType
+  deriving (Show)
+
+data Button = Button {
+  bName :: String,
+  bCost :: IntType,
+  bMove :: Vec2
+}
+  deriving (Show)
+
+data Machine = Machine {
+  mButtonA :: Button,
+  mButtonB :: Button,
+  mPrize :: Vec2
+}
+  deriving (Show)
+
+task1 :: String -> IO IntType
+task1 input = do
+  return $ sum bestPrices
+    where
+      bestPrices :: [IntType]
+      bestPrices = machines >>= maybeToList . bestPrice
+
+      machines = requireParse parseMachines input
+
+task2 :: String -> IO IntType
+task2 input = do
+  print $ zip machines (map tryCalculate machines)
+  return $ sum bestPrices
+    where
+      bestPrices :: [IntType]
+      bestPrices = machines >>= maybeToList . bestPrice
+
+      machines = requireParse parseMachines input |> map changeMachine
+
+      changeMachine :: Machine -> Machine
+      changeMachine Machine{mButtonA,mButtonB,mPrize=(Vec2 pX pY)} =
+        Machine{mButtonA,mButtonB,mPrize=(Vec2 (pX+10000000000000) (pY+10000000000000))}
+
+bestPrice :: Machine -> Maybe IntType
+bestPrice machine = tryCalculate machine |> fmap (totalCost machine)
+
+totalCost :: Machine -> Vec2 -> IntType
+totalCost Machine{mButtonA=Button{bCost=aC},mButtonB=Button{bCost=bC}} (Vec2 a b) = a*aC + b*bC
+
+tryCalculate :: Machine -> Maybe Vec2
+tryCalculate Machine{
+  mButtonA=Button{bMove=Vec2 aX aY},
+  mButtonB=Button{bMove=Vec2 bX bY},
+  mPrize=Vec2 pX pY
+} = let a = -(pY % bY - pX % bX) / (aX % bX - aY % bY)
+        an = numerator a
+  in case denominator a of
+    1 -> Just $ Vec2 an ((pX - an * aX) `div` bX)
+    _ -> Nothing
+
+safeDiv :: IntType -> IntType -> Maybe IntType
+safeDiv a b = case a `divMod` b of
+  (r, 0) -> Just r
+  _ -> Nothing
+
+requireParse :: Show a => ReadP a -> String -> a
+requireParse parser input = case readP_to_S parser input of
+  [] -> error "Failed to parse machines"
+  [(m, _)] -> m
+  alternatives -> error $ "Ambiguous input: " ++ show alternatives
+
+parseMachines :: ReadP [Machine]
+parseMachines = do
+  machines <- many1 parseMachine
+  _ <- eof
+  return machines
+
+parseMachine :: ReadP Machine
+parseMachine = do
+  buttonA <- parseButton 3
+  buttonB <- parseButton 1
+  prize <- parsePrize
+  _ <- munch isNewLine
+  return Machine { mButtonA = buttonA, mButtonB = buttonB, mPrize = prize }
+
+parseButton :: IntType -> ReadP Button
+parseButton cost = do
+  _ <- string "Button "
+  name <- many1 $ satisfy isAlpha
+  _ <- string ": X+"
+  x <- parseNumber
+  _ <- string ", Y+"
+  y <- parseNumber
+  _ <- newLine
+  return Button { bName = name, bCost = cost, bMove = Vec2 x y }
+
+parsePrize :: ReadP Vec2
+parsePrize = do
+  _ <- string "Prize: X="
+  x <- parseNumber
+  _ <- string ", Y="
+  y <- parseNumber
+  _ <- newLine
+  return $ Vec2 x y
+
+parseNumber :: ReadP IntType
+parseNumber = do
+  number <- munch1 isNumber
+  return (read number)
+
+newLine :: ReadP Char
+newLine = satisfy isNewLine
+
+isNewLine :: Char -> Bool
+isNewLine = (==) '\n'

day-13-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-13-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-13-haskell/test/Spec.hs

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