faster

glguy · Dec 20, 2024 · 84b481c · 84b481c
1 parent 0f71573
commit 84b481c
Showing 1 changed file with 9 additions and 10 deletions.
diff --git a/solutions/src/2024/20.hs b/solutions/src/2024/20.hs
@@ -11,7 +11,7 @@ Maintainer  : emertens@gmail.com
 -}
 module Main (main) where
 
-import Advent (getInputArray, arrIx)
+import Advent (getInputArray, arrIx, count)
 import Advent.Coord (cardinal, Coord, manhattan)
 import Advent.Search (astar, AStep(AStep))
 import Data.Array.Unboxed (UArray, amap, assocs, accumArray, bounds, (!))
@@ -27,15 +27,14 @@ main =
         start : _ = [p | (p,'S') <- assocs input]
         end   : _ = [p | (p,'E') <- assocs input]
         optimals  = search open end
-        cheat n   = length [()
-                  | (p1,c1) : more <- tails optimals
-                  , (p2,c2)        <- more
-                  , let d = manhattan p1 p2
-                  , d >= 2, d <= n
-                  , abs (c1 - c2) >= 100 + d
-                  ]
-    print (cheat  2)
-    print (cheat 20)
+        cheats    = [ d
+                    | (p1,c1) : more <- tails optimals
+                    , (p2,c2)        <- more
+                    , let d = manhattan p1 p2, d <= 20
+                    , abs (c1 - c2) >= 100 + d
+                    ]
+    print (count 2 cheats)
+    print (length cheats)
 
 search :: UArray Coord Bool -> Coord -> [(Coord, Int)]
 search open = astar step