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# BreadthFirstDistance

VTKEx/Cxx/Graphs/BreadthFirstDistance

### Description

This example shows how to get the distance from a vertex to the root vertex.

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

BreadthFirstDistance.cxx

    #include <vtkSmartPointer.h>

    #include <vtkBoostBreadthFirstSearch.h>
    #include <vtkDataSetAttributes.h>
    #include <vtkDoubleArray.h>
    #include <vtkIntArray.h>
    #include <vtkMutableUndirectedGraph.h>
    #include <vtkTree.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkMutableUndirectedGraph> g =
        vtkSmartPointer<vtkMutableUndirectedGraph>::New();

      // Create 3 vertices
      vtkIdType v1 = g->AddVertex();
      vtkIdType v2 = g->AddVertex();
      vtkIdType v3 = g->AddVertex();
      vtkIdType v4 = g->AddVertex();

      // Create a graph
      g->AddEdge(v1, v2);
      g->AddEdge(v1, v3);
      g->AddEdge(v2, v4);

      vtkSmartPointer<vtkBoostBreadthFirstSearch> BFS =
        vtkSmartPointer<vtkBoostBreadthFirstSearch>::New();
      BFS->SetOriginVertex(v1);
      BFS->SetInput(g);
      BFS->Update();

      vtkIntArray* level = dynamic_cast<vtkIntArray*>(
        BFS->GetOutput()->GetVertexData()->GetArray("BFS"));
      for(vtkIdType i = 0; i < level->GetNumberOfTuples(); i++)
      {
        std::cout << "id " << i << " : " << level->GetValue(i) << std::endl;
      }
      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(BreadthFirstDistance)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkCommonDataModel
      vtkvtkInfovisBoostGraphAlgorithms QUIET)
    if (NOT VTK_FOUND)
      message("Skipping BreadthFirstDistance: ${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(BreadthFirstDistance MACOSX_BUNDLE BreadthFirstDistance.cxx )
      target_link_libraries(BreadthFirstDistance PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(BreadthFirstDistance MACOSX_BUNDLE BreadthFirstDistance.cxx )
      target_link_libraries(BreadthFirstDistance PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS BreadthFirstDistance
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build BreadthFirstDistance

Click here to download BreadthFirstDistance and its CMakeLists.txt file. Once the tarball BreadthFirstDistance.tar has been downloaded and extracted,

    cd BreadthFirstDistance/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

    make

and run it:

    ./BreadthFirstDistance

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.