BGL 中顶点迭代器的次数

我正在努力从我的图中删除所有节点（使用定义的模式here http://www.boost.org/doc/libs/1_37_0/libs/graph/doc/adjacency_list.html) 没有连接边。到目前为止我的（MWE）代码如下：

//g++ -O3 question.cpp -o question.exe
#include <iostream>

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/labeled_graph.hpp>
#include <boost/graph/iteration_macros.hpp>

typedef long long node_id_t;

typedef boost::adjacency_list<
  boost::listS,           // Store out-edges of each vertex in a std::list
  boost::listS,           // Store vertex set in a std::list
  boost::bidirectionalS,  // The file dependency graph is directed
  boost::no_property,     // vertex properties
  boost::no_property      // edge properties
> AdjGraph;

typedef boost::labeled_graph<
  AdjGraph,
  node_id_t          // Node ID
> LabeledGraph;

int main(){
  LabeledGraph g;

  add_vertex( 10, g );
  add_vertex( 20, g );
  add_vertex( 30, g );
  add_vertex( 40, g );
  add_vertex( 50, g );

  boost::graph_traits<LabeledGraph>::vertex_iterator vi, vi_end, next;
  boost::tie(vi, vi_end) = boost::vertices(g);
  for (next = vi; vi != vi_end; vi = next) {
    ++next;
    if(boost::degree(*vi)==0)
      boost::remove_vertex(*vi, g);
  }
}

不幸的是，代码在编译时出错并带有投诉：

question.cpp:36:25: error: no matching function for call to ‘degree(void*&)’
 if(boost::degree(*vi)==0)

我的期望是vi is a vertex_iterator取消引用它应该给我一个有效的描述符。我不知道为什么这没有发生。

我怎样才能实现这个目标？

您需要通过额外的论点g to degree() http://www.boost.org/doc/libs/1_58_0/libs/graph/doc/BidirectionalGraph.html.

此外，由于 LabeledGraph 适配器不建模MutableGraph the remove_vertex打电话不能用。

幸运的是，您可以获得底层图表并对其进行变异。我必须阅读LabeledGraph看看是否有不良影响：

Live On Coliru http://coliru.stacked-crooked.com/a/c49fee56ec4cca7c

// g++ -O3 question.cpp -o question.exe
#include <iostream>

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/labeled_graph.hpp>
#include <boost/graph/iteration_macros.hpp>

typedef long long node_id_t;

typedef boost::adjacency_list<boost::listS,          // Store out-edges of each vertex in a std::list
                              boost::listS,          // Store vertex set in a std::list
                              boost::bidirectionalS, // The file dependency graph is directed
                              boost::no_property,    // vertex properties
                              boost::no_property     // edge properties
                              > AdjGraph;

typedef boost::labeled_graph<AdjGraph,
                             node_id_t // Node ID
                             > LabeledGraph;

int main() {
    LabeledGraph g;

    add_vertex(10, g);
    add_vertex(20, g);
    add_vertex(30, g);
    add_vertex(40, g);
    add_vertex(50, g);

    boost::graph_traits<LabeledGraph>::vertex_iterator vi, vi_end, next;

    AdjGraph& underlying = g.graph();

    boost::tie(vi, vi_end) = boost::vertices(underlying);
    for (next = vi; vi != vi_end; vi = next) {
        ++next;
        if (boost::degree(*vi, underlying) == 0)
            boost::remove_vertex(*vi, underlying);
    }
}

也许你可以不用 LabeledGraph：

Live On Coliru http://coliru.stacked-crooked.com/a/f5be3b47f9ce685c

// g++ -O3 question.cpp -o question.exe
#include <iostream>

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_utility.hpp>

typedef long long node_id_t;

typedef boost::adjacency_list<boost::listS,          // Store out-edges of each vertex in a std::list
                              boost::listS,          // Store vertex set in a std::list
                              boost::bidirectionalS, // The file dependency graph is directed
                              node_id_t,             // vertex properties
                              boost::no_property     // edge properties
                              > AdjGraph;

int main() {
    AdjGraph g;

               add_vertex(10, g);
    auto v20 = add_vertex(20, g);
               add_vertex(30, g);
    auto v40 = add_vertex(40, g);
               add_vertex(50, g);

    add_edge(v40, v20, g);

    std::cout << "BEFORE:\n";
    print_graph(g, boost::get(boost::vertex_bundle, g));

    boost::graph_traits<AdjGraph>::vertex_iterator vi, vi_end, next;

    boost::tie(vi, vi_end) = boost::vertices(g);
    for (next = vi; vi != vi_end; vi = next) {
        ++next;
        if (boost::degree(*vi, g) == 0)
            boost::remove_vertex(*vi, g);
    }

    std::cout << "\n---\nAFTER:\n";
    print_graph(g, boost::get(boost::vertex_bundle, g));
}

Prints:

BEFORE:
10 --> 
20 --> 
30 --> 
40 --> 20 
50 --> 

---
AFTER:
20 --> 
40 --> 20