remainingNeighbors :: IntMap [Int] -> IntSet -> Int -> [Int] 
remainingNeighbors graph vs = filter (flip member vs) . (graph !)
remainingNeighbors :: IntMap [Int] -> IntSet -> Int -> [Int]
remainingNeighbors graph vs = filter (flip member vs) . (graph !)
remainingNeighbors graph vs = filter (flip member vs) . (graph !)