Done day 11

diff --git a/advent11/Main.hs b/advent11/Main.hs
new file mode 100644 (file)
index 0000000..e6c72f6
--- /dev/null
+++ b/advent11/Main.hs
@@ -0,0 +1,52 @@
+-- Writeup at https://work.njae.me.uk/2024/12/11/advent-of-code-2024-day-11/
+
+import AoC
+
+-- import Data.List
+import Data.Text (Text)
+import qualified Data.Text.IO as TIO
+import Data.Attoparsec.Text -- hiding (take, takeWhile)
+import Data.IntMultiSet (IntMultiSet)
+import qualified Data.IntMultiSet as MS
+
+main :: IO ()
+main = 
+  do  dataFileName <- getDataFileName
+      text <- TIO.readFile dataFileName
+      let stones = successfulParse text
+      -- print stones
+      -- putStrLn $ unlines $ fmap show $ take 7 $ iterate blink stones
+      print $ part1 stones
+      print $ part2 stones
+
+part1, part2 :: [Int] -> Int
+part1 stones = length $ (!! 25) $ iterate blink stones
+part2 stonesList = MS.size $ (!! 75) $ iterate blinkMS stones
+  where stones = MS.fromList stonesList
+
+blink :: [Int] -> [Int]
+blink = concatMap expandStone
+
+blinkMS :: IntMultiSet -> IntMultiSet
+blinkMS = MS.concatMap expandStone 
+
+expandStone :: Int -> [Int]
+expandStone 0 = [1]
+expandStone n
+  | isEvenLen = [read nS1, read nS2]
+  | otherwise = [n * 2024]
+  where nStr = show n
+        nSL = length nStr
+        isEvenLen = nSL `mod` 2 == 0
+        (nS1, nS2) = splitAt (nSL `div` 2) nStr
+        
+-- parse the input file
+
+stonesP :: Parser [Int]
+stonesP = decimal `sepBy` " "
+
+successfulParse :: Text -> [Int]
+successfulParse input = 
+  case parseOnly stonesP input of
+    Left  _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err
+    Right stones -> stones

diff --git a/adventofcode24.cabal b/adventofcode24.cabal
index a188378d7fb6f4d232aa6bad691d7d06577c5edc..2f3eb9c92ed5779ffcdefd48dd42e745ca0336fd 100644 (file)
--- a/adventofcode24.cabal
+++ b/adventofcode24.cabal
@@ -14,10 +14,10 @@ extra-doc-files:    CHANGELOG.md
 -- extra-source-files:
 
 common warnings
-    ghc-options: -Wall
+  ghc-options: -Wall
 
 common common-modules
-    other-modules: AoC    
+  other-modules: AoC    
 
 common common-extensions
   default-extensions:     AllowAmbiguousTypes
@@ -63,7 +63,7 @@ library
 executable adventofcode24
     import:           warnings
     main-is:          Main.hs
-    -- other-modules:
+    -- other-modules:    AoC
     -- other-extensions:
     build-depends:
         base >=4.20,
@@ -128,4 +128,8 @@ executable advent10
   import: common-extensions, build-directives
   main-is: advent10/Main.hs
   build-depends: linear, array, mtl
-  
\ No newline at end of file
+  
+executable advent11
+  import: common-extensions, build-directives
+  main-is: advent11/Main.hs
+  build-depends: attoparsec, text, multiset