Optimise 11HEADmaster

1 files changed, 3 insertions, 11 deletions

diff --git a/2024/11.hs b/2024/11.hs
index 1191d17..070dd7b 100644
--- a/2024/11.hs
+++ b/2024/11.hs
@@ -1,19 +1,11 @@
-import qualified Data.Map.Strict as Map
+import qualified Data.IntMap.Strict as Map
 
 main :: IO ()
 main = do
   s0 <- map (read @Int) . words <$> getContents
-  let ndigs10 0 = 1
-      ndigs10 n = pre (4::Int)
-        where pre p | n >= 10 ^ p = pre (2*p)
-                    | otherwise = bin 0 p
-              bin lo hi | lo == hi - 1 = hi
-                        | n >= 10 ^ mid = bin mid hi
-                        | otherwise = bin lo mid
-                where mid = (lo + hi) `quot` 2
   let splitHalf n =
-        let nd = ndigs10 n
-        in if even nd then Just $ n `quotRem` (10 ^ (ndigs10 n `quot` 2))
+        let nd = length (show n)
+        in if even nd then Just $ n `quotRem` (10 ^ (nd `quot` 2))
                       else Nothing
   let blink =
         Map.fromListWith (+)