day11 first approach

aoc2024.cabal

@@ -31,6 +31,7 @@ library
       Data.Point
       Day1
       Day10
+      Day11
       Day2
       Day3
       Day4

input/day11.txt

@@ -0,0 +1 @@
+2 72 8949 0 981038 86311 246 7636740

src/Day11.hs

@@ -0,0 +1,33 @@
+module Day11 (partOne, partTwo, nextStone) where
+
+type Stone = Int
+
+partOne :: String -> Int
+partOne raw = sum $ map (blinkN 25) $ parseStones raw
+
+partTwo :: String -> Int
+partTwo raw = sum $ map (blinkN 75) $ parseStones raw
+
+blinkN :: Int -> Stone -> Int
+blinkN 0 _ = 1
+blinkN blinks stone = sum $ map (blinkN (blinks - 1)) $ nextStone stone
+
+-- blinkN blinks stone = concatMap (blinkN (blinks - 1)) (nextStone stone)
+
+nextStone :: Stone -> [Stone]
+nextStone stone
+  | stone == 0 = [1]
+  | even lengthDigits =
+      [ read $ take (lengthDigits `div` 2) digits,
+        read $ drop (lengthDigits `div` 2) digits
+      ]
+  | otherwise = [stone * 2024]
+  where
+    digits :: [Char]
+    digits = show stone
+
+    lengthDigits :: Int
+    lengthDigits = length digits
+
+parseStones :: String -> [Stone]
+parseStones = map read . words