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:
java.util.Iterator<GraphPath<V,​E>>
public class YenShortestPathIterator<V,​E>
extends java.lang.Object
implements java.util.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, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,​Pair<GraphPath<V,​E>,​java.lang.Boolean>>> heapSupplier)
    Constructs an instance of the algorithm for given graph, source, sink and heapSupplier.
    YenShortestPathIterator​(Graph<V,​E> graph, V source, V sink, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,​Pair<GraphPath<V,​E>,​java.lang.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, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,​Pair<GraphPath<V,​E>,​java.lang.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, java.util.function.Supplier<org.jheaps.AddressableHeap<java.lang.Double,​Pair<GraphPath<V,​E>,​java.lang.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 java.util.Iterator<V>

    • next

      public GraphPath<V,​E> next()
      Specified by:
      next in interface java.util.Iterator<V>