How to unite two graphs in JUNG?

StackOverflow https://stackoverflow.com/questions/7165345

  •  09-01-2021
  •  | 
  •  

Question

I have to graphs which I want to unite, that is, create a new graph composed by the union of both graph's edges and nodes (without repetition). Is there an implementation for that avaliable in JUNG or do I have do so on my own?

Was it helpful?

Solution

There isn't an implementation for that in JUNG, but it's about six lines of code assuming that the graphs, vertices, and edges are of the same types:

// given Graph g1, g2
Graph g = new [appropriate Graph implementation]
for (V v : Collections.union(g1.getVertices(), g2.getVertices())) {
  g.addVertex(v);
}
for (E e : g1.getEdges()) {
  g.addEdge(e, g1.getEndpoints(e));
}
for (E e : g2.getEdges()) {
  g.addEdge(e, g2.getEndpoints(e));
}

You can skip the vertex adding if there are no isolated vertices (i.e., vertices that have no incident edges); addEdge() will add any incident vertices.

If the graph is directed, you'll want to change the above to

g.addEdge(e, g1.getSource(e), g1.getDest(e));

Duplicates are silently ignored (if you want to know whether an add had an effect, check the return value).

Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top