Day 15

day15/Part2.hs

@@ -0,0 +1,35 @@
+module Part2 where
+
+import Commons
+import GHC.Arr (Array(Array), array, (!), (//), assocs)
+
+
+type Hashmap = Array Int [Instruction]
+
+
+initHashmap :: Hashmap
+initHashmap = array (0, 255) [(i, []) | i <- [0..255]]
+
+applyInstructionToList :: [Instruction] -> Instruction -> [Instruction]
+applyInstructionToList [] i | iType i == Set = [i]
+                            | otherwise      = []
+applyInstructionToList (h: t) i | iType i == Set && label h == label i    = i: t
+                                | iType i == Remove && label h == label i = t
+                                | otherwise                               = h: applyInstructionToList t i
+
+applyInstruction :: Hashmap -> Instruction -> Hashmap
+applyInstruction m i = let hash = getHash (label i ) 0
+                       in m // [(hash, applyInstructionToList (m ! hash) i)]
+
+applyInstructions :: [Instruction] -> Hashmap
+applyInstructions = foldl applyInstruction initHashmap
+
+getFocusingPowerFromList :: Int -> Int -> [Instruction] -> [Int]
+getFocusingPowerFromList _ _ [] = []
+getFocusingPowerFromList i slot (h: t) = i * slot * focal h: getFocusingPowerFromList i (slot + 1) t
+
+getFocusingPower :: Hashmap -> [Int]
+getFocusingPower m = concatMap (\ (i, h) -> getFocusingPowerFromList (i + 1) 1 h) (assocs m)
+
+getAllFocusingPower :: [Instruction] -> [Int]
+getAllFocusingPower = getFocusingPower . applyInstructions