org.jgrapht.alg.shortestpath

Class KShortestSimplePaths<V,E>

java.lang.Object

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

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

KShortestPathAlgorithm<V,E>

public class KShortestSimplePaths<V,E>
extends Object
implements KShortestPathAlgorithm<V,E>

The algorithm determines the k shortest simple paths in increasing order of weight. Weights can be negative (but no negative cycle is allowed), and paths can be constrained by a maximum number of edges. Graphs with multiple (parallel) edges are allowed.

The algorithm is a variant of the Bellman-Ford algorithm but instead of only storing the best path it stores the "k" best paths at each pass, yielding a complexity of $O(k \cdot n \cdot (m^2))$ where $m$ is the number of edges and $n$ is the number of vertices.

Constructor Summary

Constructors

Constructor and Description
KShortestSimplePaths(Graph<V,E> graph) Constructs an object to compute ranking shortest paths in a graph.
KShortestSimplePaths(Graph<V,E> graph, int nMaxHops) Constructs an object to calculate ranking shortest paths in a graph.
KShortestSimplePaths(Graph<V,E> graph, int nMaxHops, PathValidator<V,E> pathValidator) Constructs an object to calculate ranking shortest paths in a graph.
KShortestSimplePaths(Graph<V,E> graph, PathValidator<V,E> pathValidator) Constructs an object to compute ranking shortest paths in a graph.

Method Summary

Modifier and Type	Method and Description
List<GraphPath<V,E>>	getPaths(V startVertex, V endVertex, int k) Returns a list of the $k$ shortest simple paths in increasing order of weight.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

KShortestSimplePaths

public KShortestSimplePaths(Graph<V,E> graph)

Constructs an object to compute ranking shortest paths in a graph.

Parameters:

graph - graph on which shortest paths are searched

KShortestSimplePaths

public KShortestSimplePaths(Graph<V,E> graph,
                            PathValidator<V,E> pathValidator)

Constructs an object to compute ranking shortest paths in a graph. A non-null path validator may be used to accept/deny paths according to some external logic. These validations will be used in addition to the basic path validations which are that the path is from start to target with no loops.

Parameters:

graph - graph on which shortest paths are searched.

pathValidator - the path validator to use

KShortestSimplePaths

public KShortestSimplePaths(Graph<V,E> graph,
                            int nMaxHops)

Constructs an object to calculate ranking shortest paths in a graph.

Parameters:

graph - graph on which shortest paths are searched

nMaxHops - maximum number of edges of the calculated paths

Throws:

IllegalArgumentException - if nMaxHops is negative or 0.

KShortestSimplePaths

public KShortestSimplePaths(Graph<V,E> graph,
                            int nMaxHops,
                            PathValidator<V,E> pathValidator)

Constructs an object to calculate ranking shortest paths in a graph. A non-null path validator may be used to accept/deny paths according to some external logic. These validations will be used in addition to the basic path validations which are that the path is from start to target with no loops.

Parameters:

graph - graph on which shortest paths are searched

nMaxHops - maximum number of edges of the calculated paths

pathValidator - the path validator to use

Throws:

IllegalArgumentException - if nMaxHops is negative or 0.

Method Detail

getPaths

public List<GraphPath<V,E>> getPaths(V startVertex,
                                     V endVertex,
                                     int k)

Returns a list of the $k$ shortest simple paths in increasing order of weight.

Specified by:

getPaths in interface KShortestPathAlgorithm<V,E>

Parameters:

startVertex - source vertex of the calculated paths.

endVertex - target vertex of the calculated paths.

k - the number of shortest paths to return

Returns:

an iterator of paths between the start vertex and the end vertex

Throws:

IllegalArgumentException - if the graph does not contain the startVertex or the endVertex

IllegalArgumentException - if the startVertex and the endVertex are the same vertices

IllegalArgumentException - if k is negative or zero