# DepthFirstSearchIterator

VTKExamples/Cxx/Graphs/DepthFirstSearchIterator

### Description

This example traverses a tree in a depth first fashion.

### Code

DepthFirstSearchIterator.cxx

    #include <vtkSmartPointer.h>

    #include <vtkMutableUndirectedGraph.h>
    #include <vtkBoostPrimMinimumSpanningTree.h>
    #include <vtkBoostBreadthFirstSearch.h>
    #include <vtkTree.h>
    #include <vtkDoubleArray.h>
    #include <vtkDataSetAttributes.h>
    #include <vtkTreeDFSIterator.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();

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

      // Create the edge weight array
      vtkSmartPointer<vtkDoubleArray> weights =
        vtkSmartPointer<vtkDoubleArray>::New();
      weights->SetNumberOfComponents(1);
      weights->SetName("Weights");

      // Set the edge weights
      weights->InsertNextValue(1.0);
      weights->InsertNextValue(1.0);
      weights->InsertNextValue(2.0);

      // Add the edge weight array to the graph
      g->GetEdgeData()->AddArray(weights);

      // Output original graph info
      std::cout << "Original Graph" << std::endl << "----------" << std::endl;
      std::cout << "Number of vertices: "
                << g->GetNumberOfVertices() << std::endl;
      std::cout << "Number of edges: "
                << g->GetNumberOfEdges() << std::endl;

      // Setup the minimum spanning tree filter
      vtkSmartPointer<vtkBoostPrimMinimumSpanningTree> minimumSpanningTreeFilter =
        vtkSmartPointer<vtkBoostPrimMinimumSpanningTree>::New();
      minimumSpanningTreeFilter->SetOriginVertex(v1);
      minimumSpanningTreeFilter->SetInput(g);
      minimumSpanningTreeFilter->SetEdgeWeightArrayName("Weights");

      // Compute the minimum spanning tree
      minimumSpanningTreeFilter->Update();

      // Get the output tree
      vtkSmartPointer<vtkTree> minimumSpanningTree =
        vtkSmartPointer<vtkTree>::New();
      minimumSpanningTree->ShallowCopy(minimumSpanningTreeFilter->GetOutput());

      // Output information about the minimum spanning tree
      std::cout << std::endl;
      std::cout << "Minimum spanning tree" << std::endl
                << "----------" << std::endl;
      std::cout << "Number of vertices: "
                << minimumSpanningTree->GetNumberOfVertices() << std::endl;
      std::cout << "Number of edges: "
                << minimumSpanningTree->GetNumberOfEdges() << std::endl;

      vtkIdType root = minimumSpanningTree->GetRoot();
      std::cout << "Root: " << root << std::endl;

      vtkSmartPointer<vtkTreeDFSIterator> dFS =
        vtkSmartPointer<vtkTreeDFSIterator>::New();
      dFS->SetStartVertex(root);
      dFS->SetTree(minimumSpanningTree);

      // Traverse the tree in a depth first fashion
      while(dFS->HasNext())
      {
        vtkIdType NextVertex = dFS->Next();
        std::cout << "Next vertex: "
                  << NextVertex
                  << " level: "
                  << minimumSpanningTree->GetLevel(NextVertex)
                  << std::endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(DepthFirstSearchIterator)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(DepthFirstSearchIterator MACOSX_BUNDLE DepthFirstSearchIterator.cxx )

    target_link_libraries(DepthFirstSearchIterator ${VTK_LIBRARIES})

### Download and Build DepthFirstSearchIterator

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

    cd DepthFirstSearchIterator/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:

    ./DepthFirstSearchIterator

WINDOWS USERS

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