Question

我必须在boost库中使用kruskals算法来查找最小生成树的权重。我想我管理了那个

#include <iostream>
#include <boost/config.hpp>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/kruskal_min_spanning_tree.hpp>
#include<vector>

using namespace std;
using namespace boost;



int main(){

typedef adjacency_list <vecS,vecS,undirectedS,no_property,property <edge_weight_t,int> > Graph;

typedef graph_traits <Graph>::edge_descriptor Edge;
typedef graph_traits <Graph>::vertex_descriptor Vertex;

int a,b,c,no_vertices,no_edges;

cin>>no_vertices>>no_edges;

Graph g(no_vertices);

property_map <Graph,edge_weight_t>::type weightmap=get(edge_weight,g);
vector <Edge> spanning_tree;

for(int i=0;i<no_edges;i++)
{
    bool success;
    Edge e;
    cin>>a>>b>>c;
    tie(e,success)=add_edge(a,b,g);
    weightmap[e]=c;
}

kruskal_minimum_spanning_tree(g,back_inserter(spanning_tree));

//weight of spanning tree
int ww=0;
graph_traits<Graph>::edge_iterator ei, ei_end;
  for (tie(ei, ei_end) = edges(g); ei != ei_end; ++ei)
{
   ww=ww+weightmap[*ei];
}

cout<<"\n"<<ww;


return 0;

}

现在我需要找到顶点0和最远点之间的距离（权重之和）？关于我如何做到这一点的任何暗示？

我正在考虑使用顶点迭代器，但后来我将权重存储在weightMap中，那么如果我遍历图形的顶点，如何访问它呢？

编辑：我修改了我的程序，决定使用kruskal和prim

1.kruskal用于生成树的重量 2.prim算法，用于每个顶点距顶点0的距离（在地图距离中存储的生成树中）

不幸的是出了点问题，距离[* vertex]这是第三个顶点并没有给出答案2，但给出了一个

生成树的权重也是14而不是7

我的虚拟输入是：

这是我的节目：

#include <boost/config.hpp>
#include <iostream>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/prim_minimum_spanning_tree.hpp>
#include <boost/graph/dijkstra_shortest_paths.hpp>
#include <boost/graph/kruskal_min_spanning_tree.hpp>
using namespace std;

int
main()
{
  using namespace boost;

  typedef adjacency_list < vecS, vecS, undirectedS,
    property<vertex_distance_t, int>, property < edge_weight_t, int > > Graph;

    int num_nodes,num_edges,a,b,c;
    cin>>num_nodes>>num_edges;



  Graph g(num_nodes);

  property_map<Graph, edge_weight_t>::type weightmap = get(edge_weight, g);

  for (int j = 0; j < num_edges ; ++j) {
        cin>>a>>b>>c;
    graph_traits<Graph>::edge_descriptor e;
  bool inserted;
    tie(e, inserted) = add_edge(a, b, g);
    weightmap[e] = c;
  }

    vector < graph_traits < Graph >::vertex_descriptor > p(num_vertices(g));
    cout<<num_vertices(g);


  property_map<Graph, vertex_distance_t>::type distance = get(vertex_distance, g);
  property_map<Graph, vertex_index_t>::type indexmap = get(vertex_index, g);

  prim_minimum_spanning_tree
    (g, *vertices(g).first, &p[0], distance, weightmap, indexmap,
     default_dijkstra_visitor());

  vector <graph_traits<Graph>::edge_descriptor> spanning_tree;

  kruskal_minimum_spanning_tree(g,back_inserter(spanning_tree));
  int ww=0;
  typedef graph_traits < Graph >::edge_descriptor Edge;

  for (vector<Edge>::iterator et= spanning_tree.begin(); et != spanning_tree.end(); ++et)
{
   ww=ww+weightmap[*et];
}

typedef graph_traits<Graph>::vertex_iterator vertex_iter;
std::pair<vertex_iter, vertex_iter> vp;
for (vp = vertices(g); vp.first != vp.second; ++vp.first)
{
    cout<<distance[*vp.first];
}






prim_minimum_spanning_tree
    (g, *vertices(g).first, &p[0], distance, weightmap, indexmap,
     default_dijkstra_visitor());

  return EXIT_SUCCESS;
}

感谢你：）

Answer 1

我不确定如何解释Kruskal MST算法的结果（特别是边缘列表）。这可能是你想要的：

int ww = 0;
for (auto const& e : spanning_tree) {
    std::cout << "Traversing: " << source(e,g) << " -> " << target(e,g) << ", cost " << weightmap[e] << "\n";
    ww += weightmap[e];
}

cout << "\n" << ww;

否则，您可能希望将前任地图传递给Kruskal，并将其读取为您所需的路径。

同时请参阅上面的草图 Live On Coliru

提升kruskal算法找到顶点0和距离顶点最远的边之和？

1 个答案: