一道 Python dfs 题

def recursive_dfs(graph, start, path=None):
    if path is None:
        path = []
    path.append(start)
    for node in graph[start]:
        if not node in path:
            recursive_dfs(graph, node, path)
    return path

def recursive_dfs(graph, start, path=[]):
    path.append(start)
    for node in graph[start]:
        if not node in path:
            recursive_dfs(graph, node, path)
    return path

def recursive_dfs(graph, start, path=list()):
    path.append(start)
    for node in graph[start]:
        if not node in path:
        recursive_dfs(graph, node, path)
    return path

recursive_dfs([[1,2], [0], [3], [1]], 0)

以上 3 个都没发现问题。但正确的只有第一个。