Initial opendaylight infrastructure commit!!

[controller.git] / third-party / net.sf.jung2 / src / main / java / edu / uci / ics / jung / algorithms / cluster / WeakComponentClusterer.java

diff --git a/third-party/net.sf.jung2/src/main/java/edu/uci/ics/jung/algorithms/cluster/WeakComponentClusterer.java b/third-party/net.sf.jung2/src/main/java/edu/uci/ics/jung/algorithms/cluster/WeakComponentClusterer.java
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+/*
+* Copyright (c) 2003, the JUNG Project and the Regents of the University 
+* of California
+* All rights reserved.
+*
+* This software is open-source under the BSD license; see either
+* "license.txt" or
+* http://jung.sourceforge.net/license.txt for a description.
+*/
+package edu.uci.ics.jung.algorithms.cluster;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.commons.collections15.Buffer;
+import org.apache.commons.collections15.Transformer;
+import org.apache.commons.collections15.buffer.UnboundedFifoBuffer;
+
+import edu.uci.ics.jung.graph.Graph;
+
+
+
+/**
+ * Finds all weak components in a graph as sets of vertex sets.  A weak component is defined as
+ * a maximal subgraph in which all pairs of vertices in the subgraph are reachable from one
+ * another in the underlying undirected subgraph.
+ * <p>This implementation identifies components as sets of vertex sets.  
+ * To create the induced graphs from any or all of these vertex sets, 
+ * see <code>algorithms.filters.FilterUtils</code>.
+ * <p>
+ * Running time: O(|V| + |E|) where |V| is the number of vertices and |E| is the number of edges.
+ * @author Scott White
+ */
+public class WeakComponentClusterer<V,E> implements Transformer<Graph<V,E>, Set<Set<V>>> 
+{
+       /**
+     * Extracts the weak components from a graph.
+     * @param graph the graph whose weak components are to be extracted
+     * @return the list of weak components
+     */
+    public Set<Set<V>> transform(Graph<V,E> graph) {
+
+        Set<Set<V>> clusterSet = new HashSet<Set<V>>();
+
+        HashSet<V> unvisitedVertices = new HashSet<V>(graph.getVertices());
+
+        while (!unvisitedVertices.isEmpty()) {
+               Set<V> cluster = new HashSet<V>();
+            V root = unvisitedVertices.iterator().next();
+            unvisitedVertices.remove(root);
+            cluster.add(root);
+
+            Buffer<V> queue = new UnboundedFifoBuffer<V>();
+            queue.add(root);
+
+            while (!queue.isEmpty()) {
+                V currentVertex = queue.remove();
+                Collection<V> neighbors = graph.getNeighbors(currentVertex);
+
+                for(V neighbor : neighbors) {
+                    if (unvisitedVertices.contains(neighbor)) {
+                        queue.add(neighbor);
+                        unvisitedVertices.remove(neighbor);
+                        cluster.add(neighbor);
+                    }
+                }
+            }
+            clusterSet.add(cluster);
+        }
+        return clusterSet;
+    }
+}