/**
* Perform a DFS starting on the given node and collect all nodes that are found in the
* corresponding connected component.
*
* @param node a node.
* @param graph a graph representing a connected component, or {@code null}.
* @param visited boolean indicating for each node whether it was already visited ({@code true})
* or not.
* @param incidence list of incident edges for each node.
* @return the connected component, or {@code null} if the node was already visited.
*/
private FGraph dfs(
final FNode node,
final FGraph graph,
final boolean[] visited,
final List<FEdge>[] incidence) {
if (!visited[node.id]) {
visited[node.id] = true;
FGraph component = graph;
if (component == null) {
component = new FGraph();
}
component.getNodes().add(node);
for (FEdge edge : incidence[node.id]) {
if (edge.getSource() != node) {
dfs(edge.getSource(), component, visited, incidence);
}
if (edge.getTarget() != node) {
dfs(edge.getTarget(), component, visited, incidence);
}
component.getEdges().add(edge);
component.getLabels().addAll(edge.getLabels());
}
return component;
}
return null;
}
/**
* Creates and returns the incidence list that for each node lists the incident edges.
*
* @param graph a force graph.
*/
@SuppressWarnings("unchecked")
private List<FEdge>[] buildIncidenceLists(final FGraph graph) {
int n = graph.getNodes().size();
List<FEdge>[] incidence = new List[n];
// create incidence lists
for (FNode node : graph.getNodes()) {
incidence[node.id] = new LinkedList<FEdge>();
}
// add edges to incidence lists
for (FEdge edge : graph.getEdges()) {
incidence[edge.getSource().id].add(edge);
incidence[edge.getTarget().id].add(edge);
}
return incidence;
}