VTK/Examples/Cxx/Graphs/Conversions/TreeToMutableDirectedGraph

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkMutableDirectedGraph.h>
#include <vtkDirectedGraph.h>
#include <vtkTree.h>
 
int main (int, char *[])
{
 
  //create a graph
  vtkSmartPointer<vtkMutableDirectedGraph> mdg =
    vtkSmartPointer<vtkMutableDirectedGraph>::New();
 
  //add 4 vertices to the graph
  vtkIdType v1 = mdg->AddVertex();
  vtkIdType v2 = mdg->AddVertex();
  vtkIdType v3 = mdg->AddVertex();
  vtkIdType v4 = mdg->AddVertex();
 
  //add 3 edges to the graph
  mdg->AddEdge ( v1, v2 );
  mdg->AddEdge ( v1, v3 );
  mdg->AddEdge ( v1, v4 );
 
  //create 4 points - one for each vertex
  vtkSmartPointer<vtkPoints> points =
      vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0.0, 0.0, 0.0);
  points->InsertNextPoint(1.0, 0.0, 0.0);
  points->InsertNextPoint(0.0, 1.0, 0.0);
  points->InsertNextPoint(0.0, 0.0, 2.0);
 
  //add the coordinates of the points to the graph
  mdg->SetPoints(points);
 
  std::cout << "MDG: " << std::endl;
  std::cout << "Type: " << mdg->GetClassName() << std::endl;
  std::cout << "Vertices: " << mdg->GetNumberOfVertices() << std::endl;
  std::cout << "Edges: " << mdg->GetNumberOfEdges() << std::endl;
 
  vtkSmartPointer<vtkTree> tree =
    vtkSmartPointer<vtkTree>::New();
  tree->CheckedShallowCopy(mdg);
 
  std::cout << "Tree: " << std::endl;
  std::cout << "Type: " << tree->GetClassName() << std::endl;
  std::cout << "Vertices: " << tree->GetNumberOfVertices() << std::endl;
  std::cout << "Edges: " << tree->GetNumberOfEdges() << std::endl;
 
  vtkSmartPointer<vtkMutableDirectedGraph> mdg2 =
      vtkSmartPointer<vtkMutableDirectedGraph>::New();
  if(!mdg2->CheckedShallowCopy(tree))
    {
    std::cerr << "Could not convert!" << std::endl;
    return EXIT_FAILURE;
    }
 
  std::cout << "MDG2: " << std::endl;
  std::cout << "Type: " << mdg2->GetClassName() << std::endl;
  std::cout << "Vertices: " << mdg2->GetNumberOfVertices() << std::endl;
  std::cout << "Edges: " << mdg2->GetNumberOfEdges() << std::endl;
 
  return EXIT_SUCCESS;
}