Module org.jgrapht.core

Package org.jgrapht.traverse

Class DepthFirstIterator<V,E>

java.lang.Object

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

org.jgrapht.traverse.CrossComponentIterator<V,E,DepthFirstIterator.VisitColor>

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

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

Iterator<V>, GraphIterator<V,E>

public class DepthFirstIterator<V,E>
extends CrossComponentIterator<V,E,DepthFirstIterator.VisitColor>

A depth-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.

Author:

Liviu Rau, Barak Naveh

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	DepthFirstIterator.VisitColor	Standard vertex visit state enumeration.

Field Summary

Fields

Modifier and Type	Field	Description
static Object	SENTINEL	Sentinel object.

Fields inherited from class org.jgrapht.traverse.AbstractGraphIterator

crossComponentTraversal, graph, nListeners, reusableEdgeEvent, reusableVertexEvent, reuseEvents

Constructor Summary

Constructors

Constructor	Description
DepthFirstIterator(Graph<V,E> g)	Creates a new depth-first iterator for the specified graph.
DepthFirstIterator(Graph<V,E> g, Iterable<V> startVertices)	Creates a new depth-first iterator for the specified graph.
DepthFirstIterator(Graph<V,E> g, V startVertex)	Creates a new depth-first iterator for the specified graph.

Method Summary

Modifier and Type	Method	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)	Called whenever we re-encounter a vertex.
Deque<Object>	getStack()	Retrieves the LIFO stack of vertices which have been encountered but not yet visited (WHITE).
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.

Methods inherited from class org.jgrapht.traverse.CrossComponentIterator

finishVertex, getEntireGraphVertexIterator, getSeenData, hasNext, isSeenVertex, next, putSeenData, selectOutgoingEdges

Methods inherited from class org.jgrapht.traverse.AbstractGraphIterator

addTraversalListener, createEdgeTraversalEvent, createVertexTraversalEvent, fireConnectedComponentFinished, fireConnectedComponentStarted, fireEdgeTraversed, fireVertexFinished, fireVertexTraversed, getGraph, isCrossComponentTraversal, isReuseEvents, remove, removeTraversalListener, setCrossComponentTraversal, 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

Field Detail

SENTINEL

public static final Object SENTINEL

Sentinel object. Unfortunately, we can't use null, because ArrayDeque won't accept those. And we don't want to rely on the caller to provide a sentinel object for us. So we have to play typecasting games.

Constructor Detail

DepthFirstIterator

public DepthFirstIterator(Graph<V,E> g)

Creates a new depth-first iterator for the specified graph.

Parameters:

g - the graph to be iterated.

DepthFirstIterator

public DepthFirstIterator(Graph<V,E> g,
                          V startVertex)

Creates a new depth-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.

Throws:

IllegalArgumentException - if g does not contain startVertex

NullPointerException - if g is null

DepthFirstIterator

public DepthFirstIterator(Graph<V,E> g,
                          Iterable<V> startVertices)

Creates a new depth-first iterator for the specified graph. Iteration will start at the specified start vertices and will be limited to the connected component that includes those vertices. If the specified start vertices 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.

startVertices - the vertices iteration to be started.

Throws:

IllegalArgumentException - if startVertices contains an element that is not a vertex of g

NullPointerException - if g is null

Method Detail

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,DepthFirstIterator.VisitColor>

Returns:

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

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,DepthFirstIterator.VisitColor>

Parameters:

vertex - the vertex encountered

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

encounterVertexAgain

protected void encounterVertexAgain(V vertex,
                                    E edge)

Description copied from class: CrossComponentIterator

Called whenever we re-encounter a vertex. The default implementation does nothing.

Specified by:

encounterVertexAgain in class CrossComponentIterator<V,E,DepthFirstIterator.VisitColor>

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,DepthFirstIterator.VisitColor>

Returns:

the next vertex to be returned by this iterator.

getStack

public Deque<Object> getStack()

Retrieves the LIFO stack of vertices which have been encountered but not yet visited (WHITE). This stack also contains sentinel entries representing vertices which have been visited but are still GRAY. A sentinel entry is a sequence (v, SENTINEL), whereas a non-sentinel entry is just (v).

Returns:

stack