Day 15

day15/Part2.hs

@@ -0,0 +1,36 @@
+module Part2 where
+
+import Commons
+import Data.Array (Array, array, (!), (//), assocs, listArray)
+
+
+type Lens = (String, Int)
+type Hashmap = Array Int [Lens]
+
+initHashmap :: Hashmap
+initHashmap = listArray (0, 255) [[] | _ <- [0..255]]
+
+
+applyInstructionToList :: [Lens] -> Instruction -> [Lens]
+applyInstructionToList [] i | iType i == Set = [(label i, focal i)]
+                            | otherwise      = []
+applyInstructionToList ((l, f): t) i | iType i == Set && label i == l    = (label i, focal i): t
+                                     | iType i == Remove && label i == l = t
+                                     | otherwise                         = (l, f): applyInstructionToList t i
+
+applyInstruction :: Hashmap -> Instruction -> Hashmap
+applyInstruction m i = let hash = getHash 0 (label i)
+                       in m // [(hash, applyInstructionToList (m ! hash) i)]
+
+applyInstructions :: [Instruction] -> Hashmap
+applyInstructions = foldl applyInstruction initHashmap
+
+getFocusingPowerFromList :: Int -> Int -> [Lens] -> [Int]
+getFocusingPowerFromList _ _ [] = []
+getFocusingPowerFromList i slot ((_, f): t) = i * slot * f: getFocusingPowerFromList i (slot + 1) t
+
+getFocusingPower :: Hashmap -> [Int]
+getFocusingPower = concatMap (\ (i, h) -> getFocusingPowerFromList (i + 1) 1 h) . assocs
+
+getAllFocusingPower :: [Instruction] -> [Int]
+getAllFocusingPower = getFocusingPower . applyInstructions