从图中移除顶点

c++ remove vertex from a graph

本文关键字：顶点      更新时间：2023-10-16

以下代码使用boost.1.46.1进行编译

#include <boost/graph/adjacency_list.hpp>
struct Node {
  int id;
};
struct Edge {
  int source;
  int target;
  int weight;
};
int main() {
  /* an adjacency_list like we need it */
  typedef boost::adjacency_list<
    boost::setS, // edge container
    boost::listS, // vertex container
    boost::bidirectionalS, // directed graph
    Node, Edge> Graph;
  typedef boost::graph_traits<Graph>::vertex_descriptor Vertex;
  Graph gp1;
  std::cout << "Number of vertices 1: " << boost::num_vertices(gp1) << std::endl;
  Vertex v1 = boost::add_vertex(gp1);
  Vertex v2 = boost::add_vertex(gp1);
  std::cout << "Number of vertices 2: " << boost::num_vertices(gp1) << std::endl;
  gp1[v1].id = 3;
  gp1[v2].id = 4;
  Graph gp2(gp1);
  std::cout << "Number of vertices 3: " << boost::num_vertices(gp2) << std::endl;
  boost::remove_vertex(v2, gp2);
  std::cout << "Number of vertices 4: " << boost::num_vertices(gp1) << std::endl;
  std::cout << "Number of vertices 5: " << boost::num_vertices(gp2) << std::endl;
  boost::graph_traits<Graph>::vertex_iterator it, end;
  for (boost::tie( it, end ) = vertices(gp2); it != end; ++it) {
    if ( gp2[*it].id == 3 ) {
      boost::remove_vertex(*it, gp2);
    }
  }
  std::cout << "Number of vertices 6: " << boost::num_vertices(gp1) << std::endl;
  std::cout << "Number of vertices 7: " << boost::num_vertices(gp2) << std::endl;
  return 0;
}

gp2是如何知道v2在:"boost::remove_vertex(v2, gp2)"为什么gp1的顶点数减少了1?

为什么在:"boost::remove_vertex(*it, gp2)"会出现分割错误?我该怎么补救呢?

请注意，sehe的解决方案仅适用于具有VertexList=listS的图形，尤其不适用于具有VertexList=vecS的图形。还要注意的是，通常你不能存储顶点描述符或迭代器，之后再删除它们，因为从Boost Graph Library网站:

void remove_vertex(vertex_descriptor u, adjacency_list&g)

…如果adjacency_list的VertexList模板参数为vecS，然后为all图的顶点描述符、边描述符和迭代器是此操作无效。的内置vertex_index_t属性每个顶点被重新编号，以便在操作后顶点索引仍然形成一个连续的范围[0,num_vertices(g)). ...

在迭代顶点集合时正在修改它。

首先收集要移除的顶点，然后移除它们。或者使用以下模式:

// Remove all the vertices. This is OK.
graph_traits<Graph>::vertex_iterator vi, vi_end, next;
tie(vi, vi_end) = vertices(G);
for (next = vi; vi != vi_end; vi = next) {
  ++next;
  remove_vertex(*vi, G);
}

样本取自本页:http://www.boost.org/doc/libs/1_47_0/libs/graph/doc/adjacency_list.html(这是谷歌返回当你寻找remove vertices boost graph)

编辑

快速翻译到您的示例中:

boost::graph_traits<Graph>::vertex_iterator vi, vi_end, next;
boost::tie(vi, vi_end) = vertices(gp2);
for (next = vi; vi != vi_end; vi = next) {
    ++next;
    if (gp2[*vi].id == 3)
        remove_vertex(*vi, gp2);
}
输出:

Number of vertices 1: 0
Number of vertices 2: 2
Number of vertices 3: 2
Number of vertices 4: 1
Number of vertices 5: 2
Number of vertices 6: 1
Number of vertices 7: 1

不再崩溃:)

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