Package org.apache.xmlgraphics.util.dijkstra

Class DijkstraAlgorithm

java.lang.Object

org.apache.xmlgraphics.util.dijkstra.DijkstraAlgorithm

public class DijkstraAlgorithm
extends Object

This is an implementation of Dijkstra's algorithm to find the shortest path for a directed graph with non-negative edge weights.

See Also:

WikiPedia on Dijkstra's Algorithm

Field Summary

Fields

Modifier and Type	Field	Description
static int	INFINITE	Infinity value for distances.

Constructor Summary

Constructors

Constructor	Description
DijkstraAlgorithm(EdgeDirectory edgeDirectory)	Main Constructor.

Method Summary

Modifier and Type	Method	Description
void	execute(Vertex start, Vertex destination)	Run Dijkstra's shortest path algorithm.
protected Iterator	getDestinations(Vertex origin)	Returns an iterator over all valid destinations for a given vertex.
int	getLowestPenalty(Vertex vertex)	Returns the lowest penalty from the start point to a given vertex.
protected int	getPenalty(Vertex start, Vertex end)	Returns the penalty between two vertices.
Vertex	getPredecessor(Vertex vertex)	Returns the vertex's predecessor on the shortest path.

Methods inherited from class java.lang.Object

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

Field Detail

INFINITE

public static final int INFINITE

Infinity value for distances.

See Also:

Constant Field Values

Constructor Detail

DijkstraAlgorithm

public DijkstraAlgorithm(EdgeDirectory edgeDirectory)

Main Constructor.

Parameters:

edgeDirectory - the edge directory this instance should work on

Method Detail

getPenalty

protected int getPenalty(Vertex start,
                         Vertex end)

Returns the penalty between two vertices.

Parameters:

start - the start vertex

end - the end vertex

Returns:

the penalty between two vertices, or 0 if no single edge between the two vertices exists.

getDestinations

protected Iterator getDestinations(Vertex origin)

Returns an iterator over all valid destinations for a given vertex.

Parameters:

origin - the origin from which to search for destinations

Returns:

the iterator over all valid destinations for a given vertex

execute

public void execute(Vertex start,
                    Vertex destination)

Run Dijkstra's shortest path algorithm. After this method is finished you can use getPredecessor(Vertex) to reconstruct the best/shortest path starting from the destination backwards.

Parameters:

start - the starting vertex

destination - the destination vertex.

getLowestPenalty

public int getLowestPenalty(Vertex vertex)

Returns the lowest penalty from the start point to a given vertex.

Parameters:

vertex - the vertex

Returns:

the lowest penalty or INFINITE if there is no route to the destination.

getPredecessor

public Vertex getPredecessor(Vertex vertex)

Returns the vertex's predecessor on the shortest path.

Parameters:

vertex - the vertex for which to find the predecessor

Returns:

the vertex's predecessor on the shortest path, or null if there is no route to the destination.