Day 6, part 1

6.hs

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+import Data.Foldable
+import Data.HashSet
+import Data.Sequence
+
+type Bank   = Seq Int
+type Config = (Bank, Data.HashSet.HashSet [Int])
+
+(%) :: Int -> Int -> Int
+(%) = mod
+
+getMaxMem :: Bank -> (Int, Int)
+getMaxMem bank =
+    foldlWithIndex (\(currIndex, currMax) index value -> if value > currMax then (index, value) else (currIndex, currMax)) (0, 0) bank
+
+nextBank :: Bank -> Bank
+nextBank bank =
+    let len = Data.Sequence.length bank
+        (index, value) = getMaxMem bank
+        zeroedBank = update index 0 bank
+        mappedBank = fmap (+ value `div` len) zeroedBank
+        indicesToUpdate = fmap (% len) [(index + 1)..(index + value % len)]
+    in  mapWithIndex (\i v -> if i `elem` indicesToUpdate then v + 1 else v) mappedBank
+
+
+cycles :: Int -> Config -> Int
+cycles count (prevBank, configs) =
+    let bank = nextBank prevBank
+        hashableBank    = Data.Foldable.toList bank
+    in  if   member hashableBank configs
+        then count + 1
+        else cycles (count + 1) (bank, insert hashableBank configs)
+
+main :: IO ()
+main = do
+    input <- readFile "6.txt"
+    let bank = Data.Sequence.fromList $ fmap read $ words input :: Bank
+    print $ cycles 0 (bank, Data.HashSet.empty)

6.txt

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+14	0	15	12	11	11	3	5	1	6	8	4	9	1	8	4