org.jgrapht.traverse

Class ClosestFirstIterator<V,E>

java.lang.Object

org.jgrapht.traverse.AbstractGraphIterator<V,E>

org.jgrapht.traverse.CrossComponentIterator<V,E,FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,E>>>

org.jgrapht.traverse.ClosestFirstIterator<V,E>

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

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 weighted path length from a start vertex, i.e. 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

Nested Class Summary

Nested classes/interfaces inherited from class org.jgrapht.traverse.CrossComponentIterator

CrossComponentIterator.VisitColor

Field Summary

Fields inherited from class org.jgrapht.traverse.AbstractGraphIterator

nListeners, reusableEdgeEvent, reusableVertexEvent, specifics

Constructor Summary

Constructors

Constructor and Description
ClosestFirstIterator(Graph<V,E> g) Creates a new closest-first iterator for the specified graph.
ClosestFirstIterator(Graph<V,E> g, V startVertex) Creates a new closest-first iterator for the specified graph.
ClosestFirstIterator(Graph<V,E> g, V startVertex, double radius) Creates a new radius-bounded closest-first iterator for the specified graph.

Method Summary

Modifier and Type	Method and Description
protected void	encounterVertex(V vertex, E edge) Update data structures the first time we see a vertex.
protected void	encounterVertexAgain(V vertex, E edge) Override superclass.
double	getShortestPathLength(V vertex) Get the weighted length of the shortest path known to the given vertex.
E	getSpanningTreeEdge(V vertex) Get the spanning tree edge reaching a vertex which has been seen already in this traversal.
protected boolean	isConnectedComponentExhausted() Returns true if there are no more uniterated vertices in the currently iterated connected component; false otherwise.
protected V	provideNextVertex() Returns the vertex to be returned in the following call to the iterator next method.
void	setCrossComponentTraversal(boolean crossComponentTraversal) Sets the cross component traversal flag - indicates whether to traverse the graph across connected components.

Methods inherited from class org.jgrapht.traverse.CrossComponentIterator

finishVertex, getGraph, getSeenData, hasNext, isSeenVertex, next, putSeenData

Methods inherited from class org.jgrapht.traverse.AbstractGraphIterator

addTraversalListener, fireConnectedComponentFinished, fireConnectedComponentStarted, fireEdgeTraversed, fireVertexFinished, fireVertexTraversed, isCrossComponentTraversal, isReuseEvents, remove, removeTraversalListener, setReuseEvents

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

forEachRemaining

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 weighted 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 weighted 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 weighted 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:

weighted 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.

isConnectedComponentExhausted

protected boolean isConnectedComponentExhausted()

Description copied from class: CrossComponentIterator

Returns true if there are no more uniterated vertices in the currently iterated connected component; false otherwise.

Specified by:

isConnectedComponentExhausted in class CrossComponentIterator<V,E,FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,E>>>

Returns:

true if there are no more uniterated vertices in the currently iterated connected component; false otherwise.

See Also:

CrossComponentIterator.isConnectedComponentExhausted()

encounterVertex

protected void encounterVertex(V vertex,
                               E edge)

Description copied from class: CrossComponentIterator

Update data structures the first time we see a vertex.

Specified by:

encounterVertex in class CrossComponentIterator<V,E,FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,E>>>

Parameters:

vertex - the vertex encountered

edge - the edge via which the vertex was encountered, or null if the vertex is a starting point

See Also:

CrossComponentIterator.encounterVertex(Object, Object)

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

provideNextVertex

protected V provideNextVertex()

Description copied from class: CrossComponentIterator

Returns the vertex to be returned in the following call to the iterator next method.

Specified by:

provideNextVertex in class CrossComponentIterator<V,E,FibonacciHeapNode<org.jgrapht.traverse.ClosestFirstIterator.QueueEntry<V,E>>>

Returns:

the next vertex to be returned by this iterator.

See Also:

CrossComponentIterator.provideNextVertex()