InEdgeIterator

#include <vtkInEdgeIterator.h>
#include <vtkMutableDirectedGraph.h>
#include <vtkMutableUndirectedGraph.h>
#include <vtkNew.h>

namespace {

void Undirected();

void Directed();

} // namespace

int main(int, char*[])
{
  Undirected();
  Directed();

  return EXIT_SUCCESS;
}

namespace {
void Undirected()
{
  vtkNew<vtkMutableUndirectedGraph> g;

  // Create a graph
  vtkIdType v0 = g->AddVertex();
  vtkIdType v1 = g->AddVertex();
  vtkIdType v2 = g->AddVertex();

  g->AddEdge(v0, v1);
  g->AddEdge(v1, v2);
  g->AddEdge(v0, v2);

  // Find all incoming edges connected to a vertex
  vtkNew<vtkInEdgeIterator> it;
  g->GetInEdges(0, it);

  while (it->HasNext())
  {
    vtkInEdgeType edge = it->Next();
    std::cout << "Edge id: " << edge.Id << " Source: " << edge.Source
              << std::endl;
  }
}

void Directed()
{
  vtkNew<vtkMutableDirectedGraph> g;

  // Create a graph
  vtkIdType v0 = g->AddVertex();
  vtkIdType v1 = g->AddVertex();
  vtkIdType v2 = g->AddVertex();

  g->AddEdge(v0, v1);
  g->AddEdge(v0, v2);

  {
    std::cout << "Finding edges connected to vertex 0" << std::endl;
    vtkNew<vtkInEdgeIterator> it;
    g->GetInEdges(0, it);

    while (it->HasNext())
    {
      vtkInEdgeType edge = it->Next();
      std::cout << "Edge id: " << edge.Id << " " << "Source: " << edge.Source
                << std::endl;
    }

    std::cout << "Nothing should be output, vertex 0 has no incoming edges!"
              << std::endl;
  }

  {
    std::cout << "Finding edges connected to vertex 1" << std::endl;
    vtkNew<vtkInEdgeIterator> it;
    g->GetInEdges(1, it);

    while (it->HasNext())
    {
      vtkInEdgeType edge = it->Next();
      std::cout << "Edge id: " << edge.Id << " " << "Source: " << edge.Source
                << std::endl;
    }
  }
}

} // namespace

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(InEdgeIterator)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "InEdgeIterator: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(InEdgeIterator MACOSX_BUNDLE InEdgeIterator.cxx )
  target_link_libraries(InEdgeIterator PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS InEdgeIterator
  MODULES ${VTK_LIBRARIES}
)

cd InEdgeIterator/build

cmake ..

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

make

./InEdgeIterator