Class EppsteinShortestPathIterator<V,E>
 java.lang.Object

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

 Type Parameters:
V
 the graph vertex typeE
 the graph edge type
 All Implemented Interfaces:
java.util.Iterator<GraphPath<V,E>>
public class EppsteinShortestPathIterator<V,E> extends java.lang.Object implements java.util.Iterator<GraphPath<V,E>>
Iterator over the shortest paths (not required to be simple) between two vertices in a graph sorted by weight.This implementation can only be used for directed simple graphs. Also for this iterator to work correctly the graph must not be modified during iteration. Currently there are no means to ensure that, nor to failfast. The results of such modifications are undefined.
First the shortest paths tree in the edge reversed graph starting at
sink
is built. Thus we get distances $d(v)$ from every vertex $v$ tosink
. We then define a sidetrack edge to be an edge, which is not in the shortest paths tree. The key observation is that every path between thesource
and thesink
can be solely determined by a subsequence of its edges which are sidetracks.Let $d(v)$ be the distance from $v$ to
sink
and $w()$ be the weight function for edges ingraph
. If $e$ connects a pair of vertices $(u, w)$, the $\delta(e)$ is defined as $w(e)+d(w)d(u)$. Intuitively, $\delta(e)$ measures how much distance is lost by being “sidetracked” along $e$ instead of taking a shortest path tosink
.The idea of the algorithm is to build a heap of sidetracks. This heap can be then traversed with breadthfirst search in order to retrieve the implicit representations of the paths between
source
andsink
.This implementation has several improvements in comparison to the original description in the article:
 An outgoing edge of vertex $v$ is inserted in the paths graph iff it is reachable from the
source
.  The cross edges in the paths graph are added only for those vertices which are reachable from the root vertex.
 Weights of the edges in the paths graph are mot maintained explicitly, because they are computed during its traversal.
 Author:
 Semen Chudakov


Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
hasNext()
GraphPath<V,E>
next()
