设计目的图的遍历 该系统的功能: a、给定一-张图， 图.上有m条路，有n个节点; b、路的种类 分为高速、省道、县道3种; C、每种路车速不一样，路堵也不一样，高速是收费 |的; d、选择一条合适的路(从时间代价，从经济代价) f、任意给定始点和终点，选择合适的路径。并给出代码

好的，这是一个关于图的遍历和路径选择的系统，主要功能包括图的建立、路的分类、车速和路况的考虑、路径的查找和选择等。下面是一个大致的代码实现。

# 定义图的节点类
class Node:
    def __init__(self, name):
        self.name = name
        self.connections = {}

    def add_connection(self, node, cost):
        self.connections[node] = cost

    def get_connections(self):
        return self.connections.keys()

    def get_cost(self, node):
        return self.connections[node]

# 定义图类
class Graph:
    def __init__(self):
        self.nodes = {}

    def add_node(self, node):
        self.nodes[node.name] = node

    def get_node(self, name):
        return self.nodes[name]

    def get_nodes(self):
        return self.nodes.keys()

# 定义路的类
class Road:
    def __init__(self, name, road_type, speed, cost):
        self.name = name
        self.road_type = road_type
        self.speed = speed
        self.cost = cost

# 定义路径类
class Path:
    def __init__(self, start_node, end_node, roads, total_cost):
        self.start_node = start_node
        self.end_node = end_node
        self.roads = roads
        self.total_cost = total_cost

# 定义图遍历算法
def dfs(graph, start_node, end_node, visited=None, path=None):
    if visited is None:
        visited = set()
    if path is None:
        path = []

    visited.add(start_node)
    path.append(start_node)

    if start_node == end_node:
        return path

    for node in graph.get_node(start_node).get_connections():
        if node.name not in visited:
            new_path = dfs(graph, node.name, end_node, visited, path)
            if new_path:
                return new_path

    path.pop()
    return None

# 定义路径选择算法
def select_path(graph, start_node, end_node):
    paths = []
    visited = set()
    queue = [(start_node, [start_node], 0)]

    while queue:
        (current_node, path, cost) = queue.pop(0)

        if current_node == end_node:
            paths.append(Path(start_node, end_node, path, cost))
        else:
            for node in graph.get_node(current_node).get_connections():
                if node.name not in visited:
                    visited.add(node.name)
                    new_cost = cost + graph.get_node(current_node).get_cost(node)
                    queue.append((node.name, path + [node.name], new_cost))

    return min(paths, key=lambda x: x.total_cost)

# 测试代码
if __name__ == '__main__':
    # 建立一个图
    graph = Graph()
    node1 = Node('A')
    node2 = Node('B')
    node3 = Node('C')
    node4 = Node('D')
    node1.add_connection(node2, 10)
    node1.add_connection(node3, 15)
    node2.add_connection(node4, 12)
    node3.add_connection(node4, 20)
    graph.add_node(node1)
    graph.add_node(node2)
    graph.add_node(node3)
    graph.add_node(node4)

    # 选择路径
    path = select_path(graph, 'A', 'D')
    print([node.name for node in path.roads])  # 输出路径

这个代码实现了一个简单的图遍历和路径选择算法，可以根据需求进行修改和扩展，来满足具体的作业要求。