各路神仙,求解一个问题 - V2EX
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deplivesb
V2EX    Python

各路神仙,求解一个问题

  •  
  •   deplivesb 2022-11-01 17:19:17 +08:00 1567 次点击
    这是一个创建于 1149 天前的主题,其中的信息可能已经有所发展或是发生改变。
    有一个形如
    [
    ['Start', 'A', [['Start', 'C', 'E', 'End'], ['Start', 'F', 'End']], [['Start', 'G', 'I', 'End'], ['Start', 'X', 'End'], ['Start', 'P', 'Q', 'End']], 'D', 'End'],
    ['Start', 'B', 'End']
    ]

    用来描述图的所有路径的列表,最外层列表的每一个字列表都是一个图从 Start 到 End 的所有路径。例如 ['Start', 'B', 'End'] 表示 Start -> B -> End 但是节点有可能是个子图,此时怎么才能将子图展开,描述成为不具有子图的路径
    比如将第一个条路径拆成
    Start A C E G I D End
    Start A C E X D End
    Start A C E P Q D End
    Start A C F G I D End
    Start A C F X D End
    Start A C F P Q D End
    这六条路径

    这也有可能是个 X-Y 问题,所以我贴上一个 gist
    https://gist.githubusercontent.com/deplives/b92f0c0ceddbed7c76cc2829f8174fa1/raw/4e721ef4dace907f2d7d4a421155d44889b01fec/graph.py
    或者说 find_all_paths 需要怎么改一下能直接产出这个图的所有不带子图的路径
    Laussan
        1
    Laussan  
       2022-11-02 00:13:55 +08:00
    要不还是存成邻接矩阵然后遍历吧,你这题里的存法看得人心肺停止...
    lookStupiToForce
        2
    lookStupiToForce  
       2022-11-03 19:36:39 +08:00
    心肺停止+1+1+1+1+1......................

    我挺佩服你写的出来 find_all_paths 还达成效果了
    但你数据结构写成这样基本没法往里加功能没法维护了:
    path 和 paths 存在互相转化且一会儿要包[]后加了才能用,一会儿却只能 append
    key 和 value 作为图得节点也需要互相转化
    导致可读性 /可理解性稀烂 pro plus max ,往里加任何东西都是工程灾难

    而且你自己给出的例子里好像也错了,后面 3 个应该是
    Start A F G I D End
    Start A F X D End
    Start A F P Q D End

    下面是我特么脑抽闲的超级蛋疼,在你的屎山上(真的,这个实现足够屎)按照你的要求想破脑袋修改测试后再特意改错得到的 find_all_paths ,你试试如果你不看最后的答案能改对不?
    反正我过了今天肯定改不对了,这破 list 和 k-v 转来转去已成天书,我弄完了都记不住也不想记

    ```python
    from itertools import product


    def extend_expanded_path(ori, new):
    if isinstance(new, list):
    if len(new) == 0:
    return ori
    else:
    return [i + j for i, j in product(ori, new)]
    else:
    return [i + [new] for i in ori]


    def print_node_list(node_list):
    p_str = ''
    for node in node_list:
    if isinstance(node, Graph):
    p_str += node.name + ','
    else:
    p_str += node + ','
    return p_str


    def find_all_paths(graph, start, end, path=None, path_expanded=None, sub_graph_flag=False):
    # path_expanded list(list)
    # print('当前图名: %s 。位于节点:%s 。后续节点:[%s]。' % (graph.name, start, print_node_list(graph[start]) if start in graph else None))
    if path is None:
    path = []
    if path_expanded is None:
    path_expanded = [[]]
    if not isinstance(start, Graph):
    if sub_graph_flag:
    if start not in ('Start', 'End'):
    path = path + [start]
    path_expanded = [i + [start] for i in path_expanded]
    else:
    path = path + [start]
    path_expanded = [i + [start] for i in path_expanded]
    if start == end:
    return [path], [path_expanded]
    if start not in graph:
    return [], [[]]
    paths = []
    paths_expanded = [[]]
    for node in graph[start]:
    if node not in path:
    if isinstance(node, Graph):
    sub_path, sub_expanded_path = find_all_paths(node, "Start", "End", None, None, True)
    path = path + [sub_path]
    path_expanded = extend_expanded_path(path_expanded, sub_expanded_path)
    new_paths, new_paths_expanded = find_all_paths(graph, node, end, path, path_expanded, sub_graph_flag)

    for new_path in new_paths:
    paths.append(new_path)

    for new_path_expanded in new_paths_expanded:
    paths_expanded.append(new_path_expanded)
    return paths, paths_expanded

    print(find_all_paths(g3, "Start", "End")[0])
    print(find_all_paths(g3, "Start", "End")[1])
    ```
    lookStupiToForce
        3
    lookStupiToForce  
       2022-11-03 19:52:51 +08:00
    v 站贴代码真费事
    这个是上面贴过一遍的错误答案的:
    https://justpaste.it/9droi

    这个是正确答案的:
    https://justpaste.it/8ijo2

    蛋疼完了,上面的正确答案就算能弄出来也不建议使用,
    所以最后 3 点改进建议:
    1. 用 1#说的邻接矩阵遍历
    2. 把你原先 find_all_paths 的结果拿出来另外做递归解析
    3. 把图结构做成单张链表,上数据库用递归查询
    deplivesb
        4
    deplivesb  
    OP
       2022-11-03 22:38:49 +08:00
    @lookStupiToForce 老哥牛逼,我也是接手的。被迫啊,我已经修修补补两周多了,这部分完全不知道咋下手。
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