undirected_dfs:如何获取边的向量

时间:2016-12-08 10:14:34

标签: c++ boost-graph

注意:下面的问题是“升级图”的背景。但问题可能是“c ++”问题或“提升图”问题。

使用 boost-graph undirected_dfs ,我试图获取边缘向量。

代码正确打印back_edge和tree_edge。

我的目标是检索边缘矢量。对于此操作,我使用边向量矢量。

因此,当找到tree_edge时,我将其存储在向量中:

edgeVisited.push_back(e);

当找到back_end时,我将这个边缘向量(edgeVisited)存储在向量向量中:

myList.push_back(edgeVisited);

在此操作之后,我检查myList的大小。结果是正确的:

std::cout << "myList size by back_edge: " << myList.size() << std::endl;

在调用undirected_dfs之后,我希望通过

获取myList
std::vector< std::vector<edge_t> > vctr = vis.GetEdges();

并通过以下方式检查尺寸:

std::cout << vctr.size() << std::endl;

但是矢量无效。

能帮助我理解为什么这个向量向量是空的吗?

Here is the whole code:
#include <iostream>
#include <string>
#include <boost/cstdlib.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/undirected_dfs.hpp>
#include <boost/graph/graphviz.hpp>

using namespace boost;
typedef adjacency_list< 
    vecS, 
    vecS, 
    undirectedS,
    no_property,
    property<edge_color_t, default_color_type> > graph_t;

typedef boost::graph_traits<graph_t>::vertex_descriptor vertex_t;
typedef boost::graph_traits < graph_t>::edge_descriptor edge_t;

struct detect_loops : public boost::dfs_visitor<>
{
    template <class edge_t, class Graph>

    void back_edge(edge_t e, const Graph& g) {
        std::cout << source(e, g) << " -- " << target(e, g) << "\n";
        edgeVisited.push_back(e);
        myList.push_back(edgeVisited);
        edgeVisited.clear();
        std::cout << "myList size by back_edge: " << myList.size() << std::endl;
    }
    template <class Graph>
    void tree_edge(edge_t e, const Graph& g) {
        std::cout << "tree_edge: " << boost::source(e, g) << " --> " << boost::target(e, g) << std::endl;
        edgeVisited.push_back( e );
    }
    //get the vectors.
    std::vector< std::vector<edge_t> >  GetEdges() const { 
        std::cout << "MyList by GetEdges : " << myList.size() << std::endl;
        return myList; 
    }

private:
    std::vector<edge_t> edgeVisited;
    std::vector< std::vector<edge_t> > myList;
};

void make(graph_t &g)
{
    //Create the graph
    boost::add_edge(0, 1, g);
    boost::add_edge(0, 2, g);
    boost::add_edge(1, 3, g);
    boost::add_edge(2, 3, g);
    boost::add_edge(2, 4, g);
    boost::add_edge(3, 5, g);
    boost::add_edge(4, 5, g);
    //print the graph
    std::ofstream f("d:\\tmp\\dot\\s13.dot");
    boost::write_graphviz(f, g);
    std::system(std::string("dot -Tsvg -Grankdir=LR -Nfontsize=24 d:\\tmp\\dot\\s13.dot > d:\\tmp\\dot\\s13.svg").c_str());
}

int main(int, char*[])
{
    graph_t g;
    make(g);

    detect_loops vis;
    undirected_dfs(g, root_vertex(vertex_t(0)).visitor(vis) .edge_color_map(get(edge_color, g)));
    std::vector< std::vector<edge_t> > vctr = vis.GetEdges();
    std::cout << vctr.size() << std::endl;

    return boost::exit_success;
}

由于

1 个答案:

答案 0 :(得分:0)

这更像是一个&#34; c ++&#34;问题。这是解决方案: 我将矢量矢量作为入口参数添加到类detect_loop

detect_loops(std::vector< std::vector<edge_t> > &vctr )

并称之为:

std::vector< std::vector<edge_t> > vctr;
detect_loops vis(vctr);

这就是全部。 感谢