如何在haskell中遍历图形？

data Graph = Graph [(Int, [Int])] -- 图形的邻接表表示

dfs :: Graph -> Int -> [Int]
dfs (Graph adjList) start = dfsHelper [start] [start]
  where
    dfsHelper :: [Int] -> [Int] -> [Int]
    dfsHelper [] visited = visited
    dfsHelper (x:xs) visited =
      let neighbors = getNeighbors x adjList
          unvisitedNeighbors = filter (`notElem` visited) neighbors
          newVisited = visited ++ unvisitedNeighbors
          newStack = xs ++ unvisitedNeighbors
      in dfsHelper newStack newVisited

    getNeighbors :: Int -> [(Int, [Int])] -> [Int]
    getNeighbors x [] = []
    getNeighbors x ((node, neighbors):rest)
      | x == node = neighbors
      | otherwise = getNeighbors x rest