问题
I seen examples of jgraph and jgrapht and there easy to follow but now sure how I would go about using the CompleteBipartiteGraph? How is the syntax to be used to instantiate the graph?
http://jgrapht.org/javadoc/
http://jgrapht.org/javadoc/org/jgrapht/generate/CompleteBipartiteGraphGenerator.html
回答1:
In response to the question "Could I still use this generator?" from the comment: You could still use it to create a complete bipartite graph, and then randomly remove some edges.
But a more straightforward approach would be to simply generate two sets of vertices and insert some random edges between them. In fact, this is so easy that I have to assume that there are additional constraints that you did not mention until now. I inserted another method where it is made sure that the bipartite graph does not contain isolated vertices (my crystal ball told be to do so...)
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import org.jgrapht.Graph;
import org.jgrapht.UndirectedGraph;
import org.jgrapht.VertexFactory;
import org.jgrapht.graph.DefaultEdge;
import org.jgrapht.graph.SimpleGraph;
public class BipartiteGraphTest
{
public static void main(String[] args)
{
UndirectedGraph<String, DefaultEdge> graph =
new SimpleGraph<String, DefaultEdge>(DefaultEdge.class);
VertexFactory<String> vertexFactory = new VertexFactory<String>()
{
int n = 0;
@Override
public String createVertex()
{
String s = String.valueOf(n);
n++;
return s;
}
};
int numVertices0 = 10;
int numVertices1 = 15;
int numEdges = 20;
generateGraph(graph, numVertices0, numVertices1, numEdges, vertexFactory);
System.out.println(graph);
}
// Creates a bipartite graph with the given numbers
// of vertices and edges
public static <V, E> void generateGraph(Graph<V, E> graph,
int numVertices0, int numVertices1, int numEdges,
final VertexFactory<V> vertexFactory)
{
List<V> vertices0 = new ArrayList<V>();
for (int i = 0; i < numVertices0; i++)
{
V v = vertexFactory.createVertex();
graph.addVertex(v);
vertices0.add(v);
}
List<V> vertices1 = new ArrayList<V>();
for (int i = 0; i < numVertices1; i++)
{
V v = vertexFactory.createVertex();
graph.addVertex(v);
vertices1.add(v);
}
// Create edges between random vertices
Random random = new Random(0);
while (graph.edgeSet().size() < numEdges)
{
int i1 = random.nextInt(vertices1.size());
V v1 = vertices1.get(i1);
int i0 = random.nextInt(vertices0.size());
V v0 = vertices0.get(i0);
graph.addEdge(v0, v1);
}
}
// Creates a bipartite graph with the given numbers
// of vertices and edges without isolated vertices
public static <V, E> void generateGraphNoIsolatedVertices(
Graph<V, E> graph, int numVertices0, int numVertices1, int numEdges,
final VertexFactory<V> vertexFactory,
List<V> vertices0, List<V> vertices1)
{
int minNumEdges = Math.max(numVertices0, numVertices0);
if (numEdges < minNumEdges)
{
System.out.println("At least " + minNumEdges + " are required to " +
"connect each of the " + numVertices0 + " vertices " +
"to any of the " + numVertices1 + " vertices");
numEdges = minNumEdges;
}
for (int i = 0; i < numVertices0; i++)
{
V v = vertexFactory.createVertex();
graph.addVertex(v);
vertices0.add(v);
}
for (int i = 0; i < numVertices1; i++)
{
V v = vertexFactory.createVertex();
graph.addVertex(v);
vertices1.add(v);
}
// Connect each vertex of the larger set with
// a random vertex of the smaller set
Random random = new Random(0);
List<V> larger = null;
List<V> smaller = null;
if (numVertices0 > numVertices1)
{
larger = new ArrayList<V>(vertices0);
smaller = new ArrayList<V>(vertices1);
}
else
{
larger = new ArrayList<V>(vertices1);
smaller = new ArrayList<V>(vertices0);
}
List<V> unmatched = new ArrayList<V>(smaller);
for (V vL : larger)
{
int i = random.nextInt(unmatched.size());
V vS = unmatched.get(i);
unmatched.remove(i);
if (unmatched.size() == 0)
{
unmatched = new ArrayList<V>(smaller);
}
graph.addEdge(vL, vS);
}
// Create the remaining edges between random vertices
while (graph.edgeSet().size() < numEdges)
{
int i0 = random.nextInt(vertices0.size());
V v0 = vertices0.get(i0);
int i1 = random.nextInt(vertices1.size());
V v1 = vertices1.get(i1);
graph.addEdge(v0, v1);
}
}
}
来源:https://stackoverflow.com/questions/22669614/java-jgrapht-bipartite-graph