Module org.jgrapht.core

Package org.jgrapht.alg.shortestpath

Class YenShortestPathIterator<V,E>

java.lang.Object

org.jgrapht.alg.shortestpath.YenShortestPathIterator<V,E>

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

Iterator<GraphPath<V,E>>

public class YenShortestPathIterator<V,E>
extends Object
implements Iterator<GraphPath<V,E>>

Iterator over the shortest loopless paths between two vertices in a graph sorted by weight.

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 main idea of this algorithm is to divide each path between the source and the sink into the root part - the part that coincides within some of the paths computed so far, and the spur part, the part that deviates from all other paths computed so far. Therefore, for each path the algorithm maintains a vertex, at which the path deviates from its "parent" path (the candidate path using which it was computed).

First the algorithm finds the shortest path between the source and the sink, which is put into the candidates heap. The source is assigned to be its deviation vertex. Then on each iteration the algorithm takes a candidate from the heap with minimum weight, puts it into the result list and builds all possible deviations from it wrt. other paths, that are in the result list. By generating spur paths starting only from the vertices that are after the deviation vertex of current path (including the deviation vertex) it is possible to avoid building duplicated candidates.

Additionally, the algorithm supports path validation by means of PathValidator.

Author:

Semen Chudakov

See Also:

• PathValidator

Constructor Summary

Constructors

Constructor	Description
YenShortestPathIterator(Graph<V,E> graph, V source, V sink)	Constructs an instance of the algorithm for given graph, source and sink.
YenShortestPathIterator(Graph<V,E> graph, V source, V sink, Supplier<org.jheaps.AddressableHeap<Double,Pair<GraphPath<V,E>,Boolean>>> heapSupplier)	Constructs an instance of the algorithm for given graph, source, sink and heapSupplier.
YenShortestPathIterator(Graph<V,E> graph, V source, V sink, Supplier<org.jheaps.AddressableHeap<Double,Pair<GraphPath<V,E>,Boolean>>> heapSupplier, PathValidator<V,E> pathValidator)	Constructs an instance of the algorithm for given graph, source, sink, heapSupplier and pathValidator.
YenShortestPathIterator(Graph<V,E> graph, V source, V sink, PathValidator<V,E> pathValidator)	Constructs an instance of the algorithm for given graph, source, sink and pathValidator.

Method Summary

Modifier and Type	Method	Description
boolean	hasNext()
GraphPath<V,E>	next()

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, remove

Constructor Details

YenShortestPathIterator

public YenShortestPathIterator(Graph<V,E> graph,
 V source,
 V sink)

Constructs an instance of the algorithm for given graph, source and sink.

Parameters:

graph - graph

source - source vertex

sink - sink vertex

YenShortestPathIterator

public YenShortestPathIterator(Graph<V,E> graph,
 V source,
 V sink,
 PathValidator<V,E> pathValidator)

Constructs an instance of the algorithm for given graph, source, sink and pathValidator. The pathValidator can be null, which will indicate that all paths are valid.

Parameters:

graph - graph

source - source vertex

sink - sink vertex

pathValidator - validator to computed paths

YenShortestPathIterator

public YenShortestPathIterator(Graph<V,E> graph,
 V source,
 V sink,
 Supplier<org.jheaps.AddressableHeap<Double,Pair<GraphPath<V,E>,Boolean>>> heapSupplier)

Constructs an instance of the algorithm for given graph, source, sink and heapSupplier.

Parameters:

graph - graph

source - source vertex

sink - sink vertex

heapSupplier - supplier of the preferable heap implementation

YenShortestPathIterator

public YenShortestPathIterator(Graph<V,E> graph,
 V source,
 V sink,
 Supplier<org.jheaps.AddressableHeap<Double,Pair<GraphPath<V,E>,Boolean>>> heapSupplier,
 PathValidator<V,E> pathValidator)

Constructs an instance of the algorithm for given graph, source, sink, heapSupplier and pathValidator. The pathValidator can be null, which will indicate that all paths are valid.

Parameters:

graph - graph

source - source vertex

sink - sink vertex

heapSupplier - supplier of the preferable heap implementation

pathValidator - validator for computed paths

Method Details

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<V>

next

public GraphPath<V,E> next()

Specified by:

next in interface Iterator<V>