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

  • Field Details

    • 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 Details

    • 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.

    • 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.

  • Method Details

    • 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