faster

glguy · Dec 16, 2023 · 6005385 · 6005385
1 parent aab7833
commit 6005385
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/solutions/src/2023/16.hs b/solutions/src/2023/16.hs
@@ -107,11 +107,12 @@ dfsOn p rep next start = loop IntSet.empty [start]
     loop !seen = \case
       [] -> []
       x : q
-        | IntSet.member r seen ->     loop seen  q
-        | otherwise            -> x : loop seen' q'
+        | slow, IntSet.member r seen ->     loop seen  q
+        | otherwise                  -> x : loop seen' q'
         where
+          slow  = p x
           r     = rep x
-          seen' = if p x then IntSet.insert r seen else seen
+          seen' = if slow then IntSet.insert r seen else seen
           q'    = next x ++ q
 
 -- A more efficient way to count the number of unique coordinates