tmp

.gitignore

@@ -1,7 +1,8 @@
 result*
 *.cabal
 dist-newstyle
-*.eventlog
+*.eventlog*
 *.prof
 *.dot
 *.pdf
+aoc24-debug.*

Main.hs

@@ -12,6 +12,7 @@ import Day7
 import Day8
 import Day9
 import Day10
+import Day11
 
 main :: IO ()
 main = do
@@ -34,5 +35,7 @@ main = do
   -- Day8.main
   -- putStrLn "Day 9"
   -- Day9.main
-  putStrLn "Day 10"
+  -- putStrLn "Day 10"
-  Day10.main
+  -- Day10.main
+  putStrLn "Day 11"
+  Day11.main

flake.nix

@@ -28,6 +28,7 @@
             ghcid
             cabal-install
             fourmolu
+            eventlog2html
           ];
         # Change the prompt to show that you are in a devShell
         shellHook = ''

inputs/day11.input

@@ -0,0 +1 @@
+5910927 0 1 47 261223 94788 545 7771

package.yaml

@@ -1,6 +1,6 @@
 name: aoc24
 
-ghc-options: -Wall -threaded
+ghc-options: -Wall -threaded -O2
 
 default-extensions:
   - OverloadedStrings
@@ -25,6 +25,7 @@ dependencies:
   - unordered-containers
   - utility-ht
   - vector
+  - MemoTrie
 
 executables:
   aoc24:
@@ -33,7 +34,7 @@ executables:
       - aoc24
   aoc24-debug:
     main: Main.hs
-    ghc-options: -Wall -threaded -rtsopts -prof #-fprof-auto
+    ghc-options: -Wall -threaded -O2 -rtsopts -prof -auto-all #-fprof-auto
     dependencies:
       - aoc24
 
@@ -50,7 +51,7 @@ library:
     - Day8
     - Day9
     - Day10
-    # - Day11
+    - Day11
     # - Day12
     # - Day13
     # - Day14

src/Day11.hs

@@ -0,0 +1,74 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
+
+module Day11 where
+
+import Data.Attoparsec.Text (Parser, decimal, parseOnly, sepBy)
+import Data.Function (fix)
+import qualified Data.Text.IO as T
+import Data.Vector (Vector)
+import qualified Data.Vector as V
+import Debug.Trace
+
+parseInput :: Parser [Int]
+parseInput = decimal `sepBy` " "
+
+-- 1. If the stone is engraved with the number 0, it is replaced by a stone
+-- engraved with the number 1.
+-- 2. If the stone is engraved with a number that has an even number of digits,
+-- it is replaced by two stones. The left half of the digits are engraved on
+-- the new left stone, and the right half of the digits are engraved on the
+-- new right stone. (The new numbers don't keep extra leading zeroes: 1000
+-- would become stones 10 and 0.)
+-- 3. If none of the other rules apply, the stone is replaced by a new stone; the
+-- old stone's number multiplied by 2024 is engraved on the new stone.
+applyRule :: Int -> Vector Int
+applyRule 0 = whnfElements $ V.singleton 1
+applyRule n
+  | even leng && n > 9 =
+      whnfElements $ V.fromList [n `div` 10 ^ half, n `mod` 10 ^ half]
+  where
+    half :: Int
+    half = leng `div` 2
+    leng :: Int
+    leng = ceiling (logBase 10 (fromIntegral n) :: Float)
+applyRule n = whnfElements $ V.singleton $ n * 2024
+
+whnfElements :: Vector a -> Vector a
+whnfElements v = V.foldl' (flip seq) () v `seq` v
+
+solveA :: Vector Int -> Int
+solveA = V.length . curry iterThis 25
+
+solveA' :: [Int] -> Int
+solveA' = sum . map (lenMemo 25)
+
+iterThis :: (Int, Vector Int) -> Vector Int
+iterThis (0, vx) = vx
+iterThis (n, vx) = iterThis (n - 1, whnfElements $ V.concatMap applyRule vx)
+
+len :: (Int -> Int -> Int) -> Int -> Int -> Int
+len _ 0 _ = 1
+len f i x = traceShow i $ sum (fmap (f (i - 1)) (applyRule x))
+
+memoize :: (Int -> a) -> (Int -> a)
+memoize f = (map f [0 ..] !!)
+
+lenMemo :: Int -> Int -> Int
+lenMemo = fix (memoize . len)
+
+solveB :: [Int] -> Int
+solveB = sum . map (lenMemo 75)
+
+inputEx :: [Int]
+inputEx = [125, 17]
+
+main :: IO ()
+main = do
+  Right input <- parseOnly parseInput <$> T.readFile "inputs/day11.input"
+  putStrLn "Part 1"
+  print $ solveA $ V.fromList inputEx
+  print $ solveA $ V.fromList input
+  print $ solveA' input
+  putStrLn "Part 2"
+  print $ solveB input