TreeBFSIterator

#include <vtkSmartPointer.h>
#include <vtkMutableDirectedGraph.h>
#include <vtkTree.h>
#include <vtkTreeBFSIterator.h>

int main(int argc, char *argv[])
{
  //create a tree
  vtkSmartPointer<vtkMutableDirectedGraph> g =
    vtkSmartPointer<vtkMutableDirectedGraph>::New();

  vtkIdType v1 = g->AddVertex();
  vtkIdType v2 = g->AddVertex();
  vtkIdType v3 = g->AddVertex();

  g->AddEdge(v1, v2);
  g->AddEdge(v1, v3);

  vtkSmartPointer<vtkTree> tree =
    vtkSmartPointer<vtkTree>::New();
  tree->CheckedShallowCopy(g);

  //setup the iterator
  vtkIdType root = 0;

  vtkSmartPointer<vtkTreeBFSIterator> bfsIterator =
      vtkSmartPointer<vtkTreeBFSIterator>::New();
  bfsIterator->SetStartVertex(root);
  bfsIterator->SetTree(tree);

  //traverse the tree in a breadth first fashion
  while(bfsIterator->HasNext())
  {
    vtkIdType nextVertex = bfsIterator->Next();
    std::cout << "Next vertex: " << nextVertex << std::endl;
  }

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(TreeBFSIterator)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel QUIET)
if (NOT VTK_FOUND)
  message("Skipping TreeBFSIterator: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(TreeBFSIterator MACOSX_BUNDLE TreeBFSIterator.cxx )
  target_link_libraries(TreeBFSIterator PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(TreeBFSIterator MACOSX_BUNDLE TreeBFSIterator.cxx )
  target_link_libraries(TreeBFSIterator PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS TreeBFSIterator
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd TreeBFSIterator/build 

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./TreeBFSIterator