Question

我对Boost图表很新。我正在尝试调整一个例子来找到使用VertexList = vecS的Dijkstra最短路径算法。我将顶点容器更改为ListS。我了解到，如果我们使用listS，我们必须为算法提供自己的vertex_index。

int main(int, char *[])
{
  typedef float Weight;
  typedef boost::property<boost::edge_weight_t, Weight> WeightProperty;
  typedef boost::property<boost::vertex_name_t, std::string> NameProperty;
  typedef boost::property<boost::vertex_index_t, int> IndexProperty;

  typedef boost::adjacency_list < boost::listS, boost::listS, boost::directedS,
  NameProperty, WeightProperty > Graph;

  typedef boost::graph_traits < Graph >::vertex_descriptor Vertex;
  typedef boost::graph_traits <Graph>::vertex_iterator Viter;

  typedef boost::property_map < Graph, boost::vertex_index_t >::type IndexMap;
  typedef boost::property_map < Graph, boost::vertex_name_t >::type NameMap;

  typedef boost::iterator_property_map < Vertex*, IndexMap, Vertex, Vertex& > PredecessorMap;
  typedef boost::iterator_property_map < Weight*, IndexMap, Weight, Weight& > DistanceMap;

  Graph g;


  Vertex v0 = boost::add_vertex(std::string("v0"), g);
  Vertex v1 = boost::add_vertex(std::string("v1"), g);
  Vertex v2 = boost::add_vertex(std::string("v2"), g);
  Vertex v3 = boost::add_vertex(std::string("v3"), g);

  Weight weight0 = 5;
  Weight weight1 = 3;
  Weight weight2 = 2;
  Weight weight3 = 4;

  boost::add_edge(v0, v1, weight0, g);
  boost::add_edge(v1, v3, weight1, g);
  boost::add_edge(v0, v2, weight2, g);
  boost::add_edge(v2, v3, weight3, g);


  std::vector<Vertex> predecessors(boost::num_vertices(g)); // To store parents
  std::vector<Weight> distances(boost::num_vertices(g)); // To store distances

  IndexMap indexMap; // = boost::get(boost::vertex_index, g);
  NameMap name;
  Viter i, iend;
 //Create our own vertex index. This is what I changed in the original code
    int c = 0;
  for (boost::tie(i, iend) = vertices(g); i != iend; ++i, ++c) {
       indexMap[*i] = c; // **Error points to this line**
       name[*i] = 'A' + c;
  }
PredecessorMap predecessorMap(&predecessors[0], indexMap);
DistanceMap distanceMap(&distances[0], indexMap);
boost::dijkstra_shortest_paths(g, v0,   boost::distance_map(distanceMap).predecessor_map(predecessorMap));


  // Extract a shortest path
  std::cout << std::endl;
  typedef std::vector<Graph::edge_descriptor> PathType;
  PathType path;
  Vertex v = v3; 
  for(Vertex u = predecessorMap[v]; 
  u != v; // Keep tracking the path until we get to the source
  v = u, u = predecessorMap[v]) // Set the current vertex to the current predecessor,     and the predecessor to one level up
  {
     std::pair<Graph::edge_descriptor, bool> edgePair = boost::edge(u, v, g);
    Graph::edge_descriptor edge = edgePair.first;
    path.push_back( edge );
  }

  // Write shortest path
  std::cout << "Shortest path from v0 to v3:" << std::endl;
  float totalDistance = 0;
  for(PathType::reverse_iterator pathIterator = path.rbegin(); pathIterator !=       path.rend(); ++pathIterator)
  {
    std::cout << name[boost::source(*pathIterator, g)] << " -> " <<     name[boost::target(*pathIterator, g)]
              << " = " << boost::get( boost::edge_weight, g, *pathIterator ) <<     std::endl;

  }

  std::cout << std::endl;

  std::cout << "Distance: " << distanceMap[v3] << std::endl;

  return EXIT_SUCCESS;
}

我收到以下错误：

/spvec.cpp:62:20：错误：'index.boost :: adj_list_vertex_property_map :: operator []中的'operator ='不匹配[与Graph = boost :: adjacency_list＆gt ;, boost :: property＆gt ;，ValueType = boost :: detail :: error_property_not_found，Reference = boost :: detail :: error_property_not_found＆amp;，Tag = boost :: vertex_index_t，boost :: adj_list_vertex_property_map :: key_type = void *]（i.std :: _ List_iterator＆lt; _Tp＆gt; ; :: operator * with _Tp = void *，_Tp＆amp; = void *＆amp;）= c'

我确信在创建自己的顶点索引时犯了一个错误。但无法确切地找出问题所在。有没有人对我做错了什么有一些建议..

Answer 1

BGL实际上有一个使用dijkstra_shortest_paths和listS / listS的示例，但它没有链接到HTML文档：http://www.boost.org/doc/libs/release/libs/graph/example/dijkstra-example-listS.cpp

错误消息试图告诉您（error: no match for ‘operator=’ in ‘index.boost::adj_list_vertex_property_map...ValueType = boost::detail::error_property_not_found...）的是vertex_index_t属性没有每顶点存储空间，这是adj_list_vertex_property_map所需要的。要解决此问题，您可以更改Graph typedef以包含vertex_index_t属性的每顶点存储空间，也可以使用“{1}}”等“外部”属性地图。< / p>

associative_property_map示例使用更改图dijkstra-example-listS.cpp的方法。要在代码中使用此方法，您可以定义：

typedef

Answer 2

如果有人对该解决方案感兴趣，按照上一个答案中的建议创建一个associative_property_map解决了这个问题：

   typedef std::map<vertex_desc, size_t>IndexMap;
   IndexMap mapIndex;
   boost::associative_property_map<IndexMap> propmapIndex(mapIndex);
   //indexing the vertices
     int i=0;
     BGL_FORALL_VERTICES(v, g, pGraph)
     {
        boost::put(propmapIndex, v, i++);
     }

然后将此顶点索引映射作为命名参数传递给dijkstra_shortest_paths（）调用。 PS：BGL_FORALL_VERTICES（）在＆lt;中定义。 boost / graph / iteration / iteration_macros.hpp＆gt;

具有VertexList的Dijkstra最短路径=增强图中的ListS

2 个答案: