Package org.jgrapht.traverse

Class ClosestFirstIterator<V,​E>

  • All Implemented Interfaces:
    java.util.Iterator<V>, GraphIterator<V,​E>
    public class ClosestFirstIterator<V,​E>
extends CrossComponentIterator<V,​E,​FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,​E>>>
    A closest-first iterator for a directed or undirected graph. For this iterator to work correctly the graph must not be modified during iteration. Currently there are no means to ensure that, nor to fail-fast. The results of such modifications are undefined.

    The metric for closest here is the path length from a start vertex. Graph.getEdgeWeight(Edge) is summed to calculate path length. Negative edge weights will result in an IllegalArgumentException. Optionally, path length may be bounded by a finite radius.

    Since:
    Sep 2, 2003
    Author:
    John V. Sichi

    • Constructor Detail

      • ClosestFirstIterator

        public ClosestFirstIterator​(Graph<V,​E> g)
        Creates a new closest-first iterator for the specified graph.
        Parameters:
        g - the graph to be iterated.

      • ClosestFirstIterator

        public ClosestFirstIterator​(Graph<V,​E> g,
                            V startVertex)
        Creates a new closest-first iterator for the specified graph. Iteration will start at the specified start vertex and will be limited to the connected component that includes that vertex. If the specified start vertex is null, iteration will start at an arbitrary vertex and will not be limited, that is, will be able to traverse all the graph.
        Parameters:
        g - the graph to be iterated.
        startVertex - the vertex iteration to be started.

      • ClosestFirstIterator

        public ClosestFirstIterator​(Graph<V,​E> g,
                            V startVertex,
                            double radius)
        Creates a new radius-bounded closest-first iterator for the specified graph. Iteration will start at the specified start vertex and will be limited to the subset of the connected component which includes that vertex and is reachable via paths of length less than or equal to the specified radius. The specified start vertex may not be null.
        Parameters:
        g - the graph to be iterated.
        startVertex - the vertex iteration to be started.
        radius - limit on path length, or Double.POSITIVE_INFINITY for unbounded search.

    • Method Detail

      • setCrossComponentTraversal

        public void setCrossComponentTraversal​(boolean crossComponentTraversal)
        Description copied from class: AbstractGraphIterator
        Sets the cross component traversal flag - indicates whether to traverse the graph across connected components.
        Overrides:
        setCrossComponentTraversal in class AbstractGraphIterator<V,​E>
        Parameters:
        crossComponentTraversal - if true traverses across connected components.

      • getShortestPathLength

        public double getShortestPathLength​(V vertex)
        Get the length of the shortest path known to the given vertex. If the vertex has already been visited, then it is truly the shortest path length; otherwise, it is the best known upper bound.
        Parameters:
        vertex - vertex being sought from start vertex
        Returns:
        length of shortest path known, or Double.POSITIVE_INFINITY if no path found yet

      • getSpanningTreeEdge

        public E getSpanningTreeEdge​(V vertex)
        Get the spanning tree edge reaching a vertex which has been seen already in this traversal. This edge is the last link in the shortest known path between the start vertex and the requested vertex. If the vertex has already been visited, then it is truly the minimum spanning tree edge; otherwise, it is the best candidate seen so far.
        Parameters:
        vertex - the spanned vertex.
        Returns:
        the spanning tree edge, or null if the vertex either has not been seen yet or is the start vertex.

      • encounterVertexAgain

        protected void encounterVertexAgain​(V vertex,
                                    E edge)
        Override superclass. When we see a vertex again, we need to see if the new edge provides a shorter path than the old edge.
        Specified by:
        encounterVertexAgain in class CrossComponentIterator<V,​E,​FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,​E>>>
        Parameters:
        vertex - the vertex re-encountered
        edge - the edge via which the vertex was re-encountered