在labeled_graph上进行breadth_first_search [英] breadth_first_search on labeled_graph

问题描述

假设以下设置，应如何使用labeled_graph调用breadth_first_search?-导致2个错误:

How should breadth_first_search be called using labeled_graph assuming the following setup? - results in 2 errors:

二进制'[':未找到采用'顶点'类型的右操作数(或没有可接受的转换)的运算符

binary '[' : no operator found which takes a right-hand operand of type 'Vertex' (or there is no acceptable conversion)

'.id'左侧的错误2必须具有class/struct/union

Error 2 left of '.id' must have class/struct/union

#include<iostream>
#include<boost/graph/adjacency_list.hpp>
#include<boost/graph/breadth_first_search.hpp>
#include <boost/graph/labeled_graph.hpp>

using namespace boost;

struct NodeInfo{int id;};
struct EdgeInfo{};

typedef boost::labeled_graph< boost::adjacency_list<
    boost::vecS, boost::vecS, boost::undirectedS, NodeInfo, EdgeInfo>,
    std::string> Graph;

typedef boost::graph_traits<Graph>::vertex_descriptor GridVertex;

class Topology 
{
public:

    Graph grid;
    std::map<std::string, GridVertex> vertices; //_id to Edge

    struct custom_visitor : public boost::default_bfs_visitor
    {
        Graph& grid;

        custom_visitor(Graph& grid) :grid(grid)  {}

        template <typename Vertex, typename Graph>
        void discover_vertex(Vertex v, const Graph& g)
        {

            //vertex(...) in breadth_first_search is causing: 
            //binary '[' : no operator found which takes a right-hand operand of 
            //type 'Vertex' (or there is no acceptable conversion)  
            //left of .id must have class...
            int m = grid[v].id;

        }
    };

    void GetShortestPath(std::string s_id, std::string t_id)
    {
        custom_visitor vis(grid);

        //vertex(...) causes error
        breadth_first_search(grid.graph(), vertex(vertices[s_id],grid.graph()), visitor(vis));
    }

    void BuildNet()
    {
        Graph g;
        GridVertex v;

        v = add_vertex("A", NodeInfo(), g);
        vertices["A"] = v;

        v = add_vertex("B", NodeInfo(), g);
        vertices["B"] = v;

        add_edge_by_label("A", "B", EdgeInfo(), g);
    }
};


int main()
{
    Topology net;
    net.GetShortestPath("A", "B");
    return 0;
}

推荐答案

为什么要使用labelled_graph?

Why are you using labeled_graph?

标签图与 just adjacency_list的界面不同.这不足为奇，因为否则会是什么意思:)

Labeled graph has a different interface from just adjacency_list. This is not surprising, because, what would be the point otherwise :)

因此，如果 vertex(...)导致错误，请使用 grid.vertex(s_id):

breadth_first_search(grid.graph(), grid.vertex(s_id), visitor(vis));

在访问者中，使用实际图形，以便可以使用其 operator [] :

In the visitor, use the actual graph so you can use its operator[]:

int m = grid.graph()[v].id;

或者，实际上，为什么不使用存在的第二个参数来实现这一目的:

Or, in fact why not use the second parameter which exists for the purpose:

void discover_vertex(Vertex v, const Graph& g) {
    int m = g[v].id;
}

通过代码做出明智的示例: 在Coliru上直播

An effort to make a sensible example from the code: Live On Coliru

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