Package org.jgrapht.alg

Class ConnectivityInspector<V,​E>

  • Type Parameters:
    V - the graph vertex type
    E - the graph edge type
    All Implemented Interfaces:
    java.util.EventListener, GraphListener<V,​E>, VertexSetListener<V>
    public class ConnectivityInspector<V,​E>
extends java.lang.Object
implements GraphListener<V,​E>
    Allows obtaining various connectivity aspects of a graph. The inspected graph is specified at construction time and cannot be modified. Currently, the inspector supports connected components for an undirected graph and weakly connected components for a directed graph. To find strongly connected components, use KosarajuStrongConnectivityInspector instead.

    The inspector methods work in a lazy fashion: no computation is performed unless immediately necessary. Computation are done once and results and cached within this class for future need.

    The inspector is also a GraphListener. If added as a listener to the inspected graph, the inspector will amend internal cached results instead of recomputing them. It is efficient when a few modifications are applied to a large graph. If many modifications are expected it will not be efficient due to added overhead on graph update operations. If inspector is added as listener to a graph other than the one it inspects, results are undefined.

    Since:
    Aug 6, 2003

    • Field Detail

      • connectedSets

        java.util.List<java.util.Set<V>> connectedSets

      • vertexToConnectedSet

        java.util.Map<V,​java.util.Set<V>> vertexToConnectedSet

      • graph

        private Graph<V,​E> graph

    • Constructor Detail

      • ConnectivityInspector

        public ConnectivityInspector​(UndirectedGraph<V,​E> g)
        Creates a connectivity inspector for the specified undirected graph.
        Parameters:
        g - the graph for which a connectivity inspector to be created.

      • ConnectivityInspector

        public ConnectivityInspector​(DirectedGraph<V,​E> g)
        Creates a connectivity inspector for the specified directed graph.
        Parameters:
        g - the graph for which a connectivity inspector to be created.

    • Method Detail

      • isGraphConnected

        public boolean isGraphConnected()
        Test if the inspected graph is connected. An empty graph is not considered connected.
        Returns:
        true if and only if inspected graph is connected.

      • connectedSetOf

        public java.util.Set<V> connectedSetOf​(V vertex)
        Returns a set of all vertices that are in the maximally connected component together with the specified vertex. For more on maximally connected component, see http://www.nist.gov/dads/HTML/maximallyConnectedComponent.html.
        Parameters:
        vertex - the vertex for which the connected set to be returned.
        Returns:
        a set of all vertices that are in the maximally connected component together with the specified vertex.

      • connectedSets

        public java.util.List<java.util.Set<V>> connectedSets()
        Returns a list of Set s, where each set contains all vertices that are in the same maximally connected component. All graph vertices occur in exactly one set. For more on maximally connected component, see http://www.nist.gov/dads/HTML/maximallyConnectedComponent.html.
        Returns:
        Returns a list of Set s, where each set contains all vertices that are in the same maximally connected component.

      • pathExists

        public boolean pathExists​(V sourceVertex,
                          V targetVertex)
        Tests if there is a path from the specified source vertex to the specified target vertices. For a directed graph, direction is ignored for this interpretation of path.

        Note: Future versions of this method might not ignore edge directions for directed graphs.

        Parameters:
        sourceVertex - one end of the path.
        targetVertex - another end of the path.
        Returns:
        true if and only if there is a path from the source vertex to the target vertex.

      • init

        private void init()

      • lazyFindConnectedSets

        private java.util.List<java.util.Set<V>> lazyFindConnectedSets()