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-rw-r--r--2020/14-Docking_Data/example24
-rw-r--r--2020/14-Docking_Data/second.hs77
2 files changed, 81 insertions, 0 deletions
diff --git a/2020/14-Docking_Data/example2 b/2020/14-Docking_Data/example2
new file mode 100644
index 0000000..2e961e3
--- /dev/null
+++ b/2020/14-Docking_Data/example2
@@ -0,0 +1,4 @@
+mask = 000000000000000000000000000000X1001X
+mem[42] = 100
+mask = 00000000000000000000000000000000X0XX
+mem[26] = 1
diff --git a/2020/14-Docking_Data/second.hs b/2020/14-Docking_Data/second.hs
new file mode 100644
index 0000000..d1b6f30
--- /dev/null
+++ b/2020/14-Docking_Data/second.hs
@@ -0,0 +1,77 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import Data.Bits (clearBit, setBit)
+import Data.List (foldl')
+import Data.Map qualified as M
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 208
+
+type Bits = [Maybe Bool]
+data Op = Mask Bits| Mem Int Int
+type Input = [Op]
+
+type Parser = Parsec Void String
+
+parseMask :: Parser Op
+parseMask = do
+ void $ string "mask = "
+ bits <- some $ (char '1' *> (return $ Just True)) <|> (char '0' *> (return $ Just False)) <|> (char 'X' *> (return Nothing))
+ return $ Mask bits
+
+parseMem :: Parser Op
+parseMem = do
+ void $ string "mem["
+ index <- some digitChar
+ void $ string "] = "
+ value <- some digitChar
+ return $ Mem (read index) (read value)
+
+parseOps :: Parser Input
+parseOps = do
+ ops <- some $ (parseMask <|> parseMem) <* (optional $ char '\n')
+ void $ eof
+ return $ ops
+
+parseInput :: String -> IO Input
+parseInput filename = do
+ input <- readFile filename
+ case runParser parseOps filename input of
+ Left bundle -> die $ errorBundlePretty bundle
+ Right ops -> return ops
+
+computeOp :: Int -> Bits -> [Int]
+computeOp index bits = fst $ foldl' evalBit ([index], 35) bits
+ where
+ evalBit :: ([Int], Int) -> Maybe Bool -> ([Int], Int)
+ evalBit (acc, bit) (Just False) = (acc, bit-1)
+ evalBit (acc, bit) (Just True) = (map (\x -> setBit x bit) acc, bit-1)
+ evalBit (acc, bit) Nothing = ((map (\x -> setBit x bit) acc) ++ (map (\x -> clearBit x bit) acc), bit-1)
+
+compute :: Input -> Int
+compute = extract . foldl' compute init
+ where
+ extract :: (M.Map Int Int, Bits) -> Int
+ extract = sum . M.elems . fst
+ compute :: (M.Map Int Int, Bits) -> Op -> (M.Map Int Int, Bits)
+ compute (acc, _) (Mask bits) = (acc, bits)
+ compute (acc, bits) (Mem index value) = (newAcc, bits)
+ where
+ newAcc :: M.Map Int Int
+ newAcc = foldl' eval acc (computeOp index bits)
+ eval :: M.Map Int Int -> Int -> M.Map Int Int
+ eval acc' index' = M.insert index' value acc'
+ init :: (M.Map Int Int, Bits)
+ init = (M.empty, [])
+
+main :: IO ()
+main = do
+ example <- parseInput "example2"
+ let exampleOutput = compute example
+ when (exampleOutput /= exampleExpectedOutput) (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+ input <- parseInput "input"
+ print $ compute input