AOC day 22

    mkTotals :: [[(Key,Int)]] -> ST s [(Key,Int)]
    mkTotals prices = do
      totals <- newArray bounds 0 :: ST s (STArray s Key Int)
      forM_ prices
        (\price -> do
          checks <- newArray bounds False :: ST s (STArray s Key Bool)
          forM_ price
            (\(k,v) -> do
                check <- readArray checks k
                if check then
                  return ()
                else do
                  writeArray checks k True
                  cv <- readArray totals k
                  writeArray totals k (cv + v)))
      getAssocs totals
      where
        bounds = ((-9,-9,-9,-9), (9,9,9,9))