org.jgrapht.alg.shortestpath

Class TreeSingleSourcePathsImpl<V,E>

java.lang.Object

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

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

Serializable, ShortestPathAlgorithm.SingleSourcePaths<V,E>

public class TreeSingleSourcePathsImpl<V,E>
extends Object
implements ShortestPathAlgorithm.SingleSourcePaths<V,E>, Serializable

An implementation of ShortestPathAlgorithm.SingleSourcePaths which uses linear space.

This implementation uses the traditional representation of maintaining for each vertex the predecessor in the shortest path tree. In order to keep space to linear, the paths are recomputed in each invocation of the getPath(Object) method. The complexity of getPath(Object) is linear to the number of edges of the path while the complexity of getWeight(Object) is $O(1)$.

Author:

Dimitrios Michail

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Graph<V,E>	g The graph
protected Map<V,Pair<Double,E>>	map A map which keeps for each target vertex the predecessor edge and the total length of the shortest path.
protected V	source The source vertex

Constructor Summary

Constructors

Constructor and Description
TreeSingleSourcePathsImpl(Graph<V,E> g, V source, Map<V,Pair<Double,E>> distanceAndPredecessorMap) Construct a new instance.

Method Summary

Modifier and Type	Method and Description
Map<V,Pair<Double,E>>	getDistanceAndPredecessorMap() Get the internal map used for representing the paths.
Graph<V,E>	getGraph() Returns the graph over which this set of paths is defined.
GraphPath<V,E>	getPath(V targetVertex) Return the path from the source vertex to the sink vertex.
V	getSourceVertex() Returns the single source vertex.
double	getWeight(V targetVertex) Return the weight of the path from the source vertex to the sink vertex.

Methods inherited from class java.lang.Object

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

Field Detail

g

protected Graph<V,E> g

The graph

source

protected V source

The source vertex

map

protected Map<V,Pair<Double,E>> map

A map which keeps for each target vertex the predecessor edge and the total length of the shortest path.

Constructor Detail

TreeSingleSourcePathsImpl

public TreeSingleSourcePathsImpl(Graph<V,E> g,
                                 V source,
                                 Map<V,Pair<Double,E>> distanceAndPredecessorMap)

Construct a new instance.

Parameters:

g - the graph

source - the source vertex

distanceAndPredecessorMap - a map which contains for each vertex the distance and the last edge that was used to discover the vertex. The map does not need to contain any entry for the source vertex. In case it does contain the predecessor at the source vertex must be null.

Method Detail

getGraph

public Graph<V,E> getGraph()

Returns the graph over which this set of paths is defined.

Specified by:

getGraph in interface ShortestPathAlgorithm.SingleSourcePaths<V,E>

Returns:

the graph

getSourceVertex

public V getSourceVertex()

Returns the single source vertex.

Specified by:

getSourceVertex in interface ShortestPathAlgorithm.SingleSourcePaths<V,E>

Returns:

the single source vertex

getDistanceAndPredecessorMap

public Map<V,Pair<Double,E>> getDistanceAndPredecessorMap()

Get the internal map used for representing the paths.

Returns:

the internal distance and predecessor map used for representing the paths.

getWeight

public double getWeight(V targetVertex)

Return the weight of the path from the source vertex to the sink vertex. If no such path exists, Double.POSITIVE_INFINITY is returned. The weight of the path between a vertex and itself is always zero.

Specified by:

getWeight in interface ShortestPathAlgorithm.SingleSourcePaths<V,E>

Parameters:

targetVertex - the sink vertex

Returns:

the weight of the path between source and sink vertices or Double.POSITIVE_INFINITY in case no such path exists

getPath

public GraphPath<V,E> getPath(V targetVertex)

Return the path from the source vertex to the sink vertex.

Specified by:

getPath in interface ShortestPathAlgorithm.SingleSourcePaths<V,E>

Parameters:

targetVertex - the sink vertex

Returns:

the path from the source vertex to the sink vertex or null if no such path exists