Class BreadthFirstTopologicalIterator
 Object

 AbstractGraphIterator

 BreadthFirstTopologicalIterator

 All Implemented Interfaces:
GraphIterator
 Direct Known Subclasses:
DepthFirstTopologicalIterator
public class BreadthFirstTopologicalIterator extends AbstractGraphIterator
Iterates over the nodes of a graph in Breadth First Topological Sort pattern. The following is an illustration of the iteration.
Initially all nodes of degree less than two are active (ready to be visited). As nodes are visited, a node can become active when all but one of its related nodes have been visited ( degree = counter + 1). When a node becomes active it is placed into the active node queue (queue of nodes to be visited). The Breadth First Topological iterator places nodes into the queue in First In First Out order.
To determine when a node is to become active the iterator uses the counter associated with each node. If these counters are modified by an entity other then the iterator, the iteration may be affected in undefined ways. Author:
 Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net


Constructor Summary
Constructors Constructor Description BreadthFirstTopologicalIterator()

Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected Queue<Graphable>
buildQueue(Graph graph)
Builds the active node queue.void
cont(Graphable current, GraphTraversal traversal)
Continues the iteration by incrementing the counters of any unvisited nodes related to the current node.void
init(Graph graph, GraphTraversal traversal)
Creates the active queue, and populates it with all nodes of degree less than 2.void
killBranch(Graphable current, GraphTraversal traversal)
Kills the current branch of the traversal by not incrementing the counters of any related nodes.Graphable
next(GraphTraversal traversal)
Returns the next node in the active node queue.
Methods inherited from class AbstractGraphIterator
getGraph, getTraversal, getWalker, setTraversal




Method Detail

init
public void init(Graph graph, GraphTraversal traversal)
Creates the active queue, and populates it with all nodes of degree less than 2. Counters of all nodes are also reset to 0. Parameters:
graph
 The graph being whose components are being iterated over. See Also:
org.geotools.graph.traverse.GraphIterator#init(Graph)

next
public Graphable next(GraphTraversal traversal)
Returns the next node in the active node queue. Returns:
 The next component in the iteration, or null if iteration is complete.
 See Also:
org.geotools.graph.traverse.GraphIterator#next()

cont
public void cont(Graphable current, GraphTraversal traversal)
Continues the iteration by incrementing the counters of any unvisited nodes related to the current node. If any related nodes have counters equal to degree of that node  1, it is placed into the active queue. Parameters:
current
 The current component of the traversal. See Also:
org.geotools.graph.traverse.GraphIterator#cont(Graphable)

killBranch
public void killBranch(Graphable current, GraphTraversal traversal)
Kills the current branch of the traversal by not incrementing the counters of any related nodes. Parameters:
current
 The current component of the traversal. See Also:
org.geotools.graph.traverse.GraphIterator#killBranch(Graphable)

