Day 24, a day late because I'm on vacation :/

24.hs

@@ -0,0 +1,33 @@
+import Data.List.Split (splitOn)
+import Data.Sequence (Seq, (!?), (<|), fromList, empty, findIndicesL, deleteAt)
+
+type Port = Int
+type Component = (Port, Port)
+type Bridge = Seq Component
+type Est = Bridge -> (Int, Bridge) -> (Int, Bridge)
+
+bridgeStrength :: Bridge -> Int
+bridgeStrength components = sum . fmap (uncurry (+)) $ components
+
+strongest :: Est
+strongest bridge s@(currStrength, _) =
+    if bridgeStrength bridge > currStrength then (bridgeStrength bridge, bridge) else s
+
+longest :: Est
+longest bridge l@(currLength, _) =
+    if length bridge > currLength then (length bridge, bridge) else l
+
+estBridge :: Est -> Port -> Bridge -> Bridge
+estBridge est port components =
+    let indicesOfPort = findIndicesL (\(a, b) -> a == port || b == port) components
+        subbridges    = map subbridge indicesOfPort
+    in  snd $ foldr est (0, empty) subbridges
+    where subbridge i =
+            let Just c@(a, b) = components !? i
+            in  c <| estBridge est (if a == port then b else a) (deleteAt i components)
+
+main :: IO ()
+main = do
+    components <- fromList . map (\line -> let a : b : [] = splitOn "/" line in (read a, read b)) . lines <$> readFile "24.txt"
+    print $ bridgeStrength $ estBridge strongest 0 components
+    print $ bridgeStrength $ estBridge longest   0 components

24.txt

@@ -0,0 +1,55 @@
+50/41
+19/43
+17/50
+32/32
+22/44
+9/39
+49/49
+50/39
+49/10
+37/28
+33/44
+14/14
+14/40
+8/40
+10/25
+38/26
+23/6
+4/16
+49/25
+6/39
+0/50
+19/36
+37/37
+42/26
+17/0
+24/4
+0/36
+6/9
+41/3
+13/3
+49/21
+19/34
+16/46
+22/33
+11/6
+22/26
+16/40
+27/21
+31/46
+13/2
+24/7
+37/45
+49/2
+32/11
+3/10
+32/49
+36/21
+47/47
+43/43
+27/19
+14/22
+13/43
+29/0
+33/36
+2/6

README.md

@@ -31,7 +31,8 @@ These are the runtimes of only one trial but the variances are fairly small and
 | 20  |  0.168      |
 | 21  |  4.013      |
 | 22  | 12.867      |  7.880
-| 23  |  0.274      | 
+| 23  |  0.274      |
+| 24  |  6.887      |
 
 Problems that could use some work: 05, 22, 14, 15, 21, 17