Question

我试图在以下链接的帮助下创建图形但是当我使用find_path方法时，我返回了错误的路径。链接：

http://www.python-course.eu/graphs_python.php

代码：

class Graph(object):
    def __init__(self, graph_dict=None):
        """ initializes a graph object
            If no dictionary or None is given, an empty dictionary will be used
        """
        if graph_dict is None:
            graph_dict = {}
        self.__graph_dict = graph_dict

    def find_path(self, start_vertex, end_vertex, path=[]):
        """ find a path from start_vertex to end_vertex
            in graph """
        graph = self.__graph_dict
        path = path + [start_vertex]
        if start_vertex == end_vertex:
            return path
        if start_vertex not in graph:
            return None
        for vertex in graph[start_vertex]:
            if vertex not in path:
                extended_path = self.find_path(vertex,
                                               end_vertex,
                                               path)
                if extended_path:
                    return extended_path
        return None

g = {"a": ["c", "d"],
     "b": ["a", "c"],
     "c": ["a", "b", "c", "d", "e"],
     "d": ["c", "e"],
     "e": ["c", "f"],
     "f": ["c"]
     }

graph = Graph(g)

"""
graph:

a<----b         <-- one way
|\   /          --- two way
| \ /
|  c <-- f
| / \    ^
v/   \   |
d---->e--/

"""
print graph.find_path("b", "f")

Output: ['b', 'a', 'c', 'd', 'e', 'f']
Should be: ['b', 'a', 'd', 'e', 'f']

Graph类中的find_path方法有什么问题？

Answer 1

您对此进行了编程以找到任何非循环路径，然后返回找到的第一个路径。它找到的路径非常合理;它不是最少的步骤。

要找到最短路径，您需要实现广度优先搜索或带记忆的深度优先搜索（跟踪每个节点的最佳已知路径）。 Dijkstra的算法适用于最短路径。

为什么图形找不到正确的路径？

1 个答案: