/**
* Create a copy of a graph for internal use.
*
* @param graph the graph to copy.
* @return A copy of the graph projected to a SimpleGraph.
*/
private static <V, E> UndirectedGraph<V, E> copyAsSimpleGraph(UndirectedGraph<V, E> graph) {
UndirectedGraph<V, E> copy = new SimpleGraph<>(graph.getEdgeFactory());
if (graph instanceof SimpleGraph) {
Graphs.addGraph(copy, graph);
} else {
// project graph to SimpleGraph
Graphs.addAllVertices(copy, graph.vertexSet());
for (E e : graph.edgeSet()) {
V v1 = graph.getEdgeSource(e);
V v2 = graph.getEdgeTarget(e);
if ((v1 != v2) && !copy.containsEdge(e)) {
copy.addEdge(v1, v2);
}
}
}
return copy;
}
