为什么我修改函数中的列表后没有得到任何结果？

Question

我编写了一个 dfs 函数并返回所有可能的从起点到目的地点的路径。 但是，我注意到我在函数中得到了正确的路径，但我没有从函数中得到它。

res = []
Solution s:
    def find all_path(graph:list(list)):
        def dfs(curNode, path: list)->list[list]:
            if curNode == target:
                #Correct one:
                #res.append(list(path))
                #Wrong one:
                res.append(path)
        
                return 
            #all other code without modify the list of res
        path = [start_point]
        dfs(start_point, path)
        return res

我为什么要写

res.append(list(path))

？我记得列表 A.append(list.B) 将获得 A[ [B] ] 格式。所以，应该没问题。

尝试过：搜索网站并尝试检查全局验证，但我以前一直这样做。只是这一次，我在外面没有得到正确的值。

期望：我想知道为什么。

Answer 1

试试这个

def find_all_paths(graph: list[list]) -> list[list]:
  """
  Find all possible paths from start to destination in a graph.

  Args:
      graph: A list of lists representing the graph.

  Returns:
      A list of lists, where each sublist is a path from start to 
destination.
  """

  start_point, target = 0, len(graph) - 1
  res = []

  def dfs(cur_node: int, path: list) -> None:
    """
    Depth-first search to find all paths from cur_node to destination.

    Args:
        cur_node: The current node.
        path: The current path.
    """
    if cur_node == target:
      # Append a copy of the current path to the results.
      res.append(list(path))
      return

    for neighbor in graph[cur_node]:
      if neighbor not in path:
        path.append(neighbor)
        dfs(neighbor, path)
        path.pop()  # Backtrack by removing the last node from the path.

      dfs(start_point, [start_point])
      return res

# Example usage
graph = [[1, 2], [0, 3, 4], [0], [1, 5], [1, 6], [4], [5]]
paths = find_all_paths(graph)
print(f"All paths from 0 to 6: {paths}")

此代码将打印以下输出：

从 0 到 6 的所有路径：[[0, 1, 3, 5, 4, 6], [0, 1, 4, 6]]