Day 5 (takes 40 seconds... too long??)

5.hs

@@ -0,0 +1,24 @@
+import Data.Sequence
+
+type Index = Int
+type Steps = Int
+type State = (Steps, Index, Seq Int)
+type Update = Int -> Int
+
+next :: Update -> State -> State
+next f (steps, i, jumps) =
+    let value = index jumps i
+        nextI = i + value
+        nextJumps = update i (f value) jumps
+    in  (steps + 1, nextI, nextJumps)
+
+getExitSteps :: Update -> State -> Int
+getExitSteps f (steps, i, jumps) =
+    if i >= Data.Sequence.length jumps then steps else getExitSteps f $ next f (steps, i, jumps)
+
+main :: IO ()
+main = do
+    input <- readFile "5.txt"
+    let jumps = fromList . map read $ lines input :: Seq Int
+    print $ getExitSteps (+1)                                    (0, 0, jumps)
+    print $ getExitSteps (\v -> if v >= 3 then v - 1 else v + 1) (0, 0, jumps)