我有一个带有顶点A..C和边E1..E4的有向多图
A ---E1--> B
A ---E2--> B
A ---E3--> B
B ---E4--> C
我想迭代连接A和B的边缘 .
在BGL中,我将此表达为:
#include <boost/graph/adjacency_list.hpp>
struct Vertex
{
std::string code;
};
struct Edge
{
double distance;
std::string code;
};
int main()
{
using namespace boost;
typedef adjacency_list<listS, vecS, directedS, Vertex, Edge> Graph;
Graph g;
auto a= add_vertex(Vertex{ "A" }, g);
auto b= add_vertex(Vertex{ "B" }, g);
auto c= add_vertex(Vertex{ "C" }, g);
add_edge(a, b, Edge{ 10, "E1" }, g);
add_edge(a, b, Edge{ 10, "E2" }, g);
add_edge(a, b, Edge{ 10, "E3" }, g);
add_edge(a, c, Edge{ 10, "E4" }, g);
// checking number of edges
std::cout<< num_edges(g)<< std::endl;
// printing edges branching from A
auto erange= out_edges(a, g);
for(auto i= erange.first; i!= erange.second; ++ i)
std::cout<< g[*i].code<< std::endl;
// now we want to iterate over edges that connect A and B
auto wtf= boost::edge_range(a, b, g);
}
这导致编译错误:
In file included from /usr/include/boost/graph/adjacency_list.hpp:246:
/usr/include/boost/graph/detail/adjacency_list.hpp:1617:25: error: no matching constructor for initialization of 'StoredEdge' (aka
'boost::detail::stored_edge_property<unsigned long, Edge>')
equal_range(el, StoredEdge(v, fake_edge_container.end(),
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
我已经阅读了文档:
std::pair<out_edge_iterator, out_edge_iterator> edge_range(vertex_descriptor u, vertex_descriptor v, const adjacency_list& g) Returns a pair of out-edge iterators that give the range for all the parallel edges from u to v. This function only works when the OutEdgeList for the adjacency_list is a container that sorts the out edges according to target vertex, and allows for parallel edges. The multisetS selector chooses such a container.
(http://www.boost.org/doc/libs/1_54_0/libs/graph/doc/adjacency_list.html)
修改了图表:
typedef adjacency_list<multisetS, vecS, directedS, Vertex, Edge> Graph;
但错误没有改变 .
那么如何使用BGL在有向多图中列出两个顶点(from-> to)之间的边?
我发现了一种快速而肮脏的方式:
auto erange= out_edges(a, g);$
for(auto i= erange.first; i!= erange.second; ++ i)$
std::cout<< g[*i].code<< " -> "<< g[target(*i, g)].code<< std::endl;$
这将让我按目标顶点过滤边缘 . 但是你如何使用 boost::edge_range
?
1 回答
此错误已在Boost mailinglist之前报告过 .
在程序中将
directedS
更改为undirectedS
可以正常工作 . Live Example . 但这可能不是您的应用程序所需要的,因此您之前提到的简单过滤器可能会更好 . 您可以在Boost邮件列表上重新发布此内容以获得更多关注 .