- java.lang.Object
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- org.jgrapht.alg.shortestpath.BaseShortestPathAlgorithm<V,E>
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- org.jgrapht.alg.shortestpath.BellmanFordShortestPath<V,E>
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- Type Parameters:
V
- the graph vertex typeE
- the graph edge type
- All Implemented Interfaces:
ShortestPathAlgorithm<V,E>
public class BellmanFordShortestPath<V,E> extends BaseShortestPathAlgorithm<V,E>
The Bellman-Ford algorithm.Computes shortest paths from a single source vertex to all other vertices in a weighted graph. The Bellman-Ford algorithm supports negative edge weights.
Negative weight cycles are not allowed and will be reported by the algorithm. This implies that negative edge weights are not allowed in undirected graphs. In such cases the code will throw an exception of type
NegativeCycleDetectedException
which will contain the detected negative weight cycle. Note that the algorithm will not report or find negative weight cycles which are not reachable from the source vertex.The running time is $O(|E||V|)$.
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Nested Class Summary
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Nested classes/interfaces inherited from interface org.jgrapht.alg.interfaces.ShortestPathAlgorithm
ShortestPathAlgorithm.SingleSourcePaths<V,E>
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Field Summary
Fields Modifier and Type Field Description protected java.util.Comparator<java.lang.Double>
comparator
protected int
maxHops
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Fields inherited from class org.jgrapht.alg.shortestpath.BaseShortestPathAlgorithm
graph, GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE, GRAPH_MUST_CONTAIN_THE_SINK_VERTEX, GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
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Constructor Summary
Constructors Constructor Description BellmanFordShortestPath(Graph<V,E> graph)
Construct a new instance.BellmanFordShortestPath(Graph<V,E> graph, double epsilon)
Construct a new instance.BellmanFordShortestPath(Graph<V,E> graph, double epsilon, int maxHops)
Construct a new instance.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description private GraphPath<V,E>
computeNegativeCycle(E edge, java.util.Map<V,E> pred)
Computes a negative weight cycle assuming that the algorithm has already determined that it exists.static <V,E>
GraphPath<V,E>findPathBetween(Graph<V,E> graph, V source, V sink)
Find a path between two vertices.GraphPath<V,E>
getPath(V source, V sink)
Get a shortest path from a source vertex to a sink vertex.ShortestPathAlgorithm.SingleSourcePaths<V,E>
getPaths(V source)
Compute all shortest paths starting from a single source vertex.-
Methods inherited from class org.jgrapht.alg.shortestpath.BaseShortestPathAlgorithm
createEmptyPath, getPathWeight
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Constructor Detail
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BellmanFordShortestPath
public BellmanFordShortestPath(Graph<V,E> graph)
Construct a new instance.- Parameters:
graph
- the input graph
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BellmanFordShortestPath
public BellmanFordShortestPath(Graph<V,E> graph, double epsilon)
Construct a new instance.- Parameters:
graph
- the input graphepsilon
- tolerance when comparing floating point values
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BellmanFordShortestPath
public BellmanFordShortestPath(Graph<V,E> graph, double epsilon, int maxHops)
Construct a new instance.- Parameters:
graph
- the input graphepsilon
- tolerance when comparing floating point valuesmaxHops
- execute the algorithm for at most this many iterations. If this is smaller than the number of vertices, then the negative cycle detection feature is disabled.- Throws:
java.lang.IllegalArgumentException
- if the number of maxHops is not positive
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Method Detail
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getPath
public GraphPath<V,E> getPath(V source, V sink)
Get a shortest path from a source vertex to a sink vertex.- Parameters:
source
- the source vertexsink
- the target vertex- Returns:
- a shortest path or null if no path exists
- Throws:
NegativeCycleDetectedException
- in case a negative weight cycle is detected
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getPaths
public ShortestPathAlgorithm.SingleSourcePaths<V,E> getPaths(V source)
Compute all shortest paths starting from a single source vertex.- Specified by:
getPaths
in interfaceShortestPathAlgorithm<V,E>
- Overrides:
getPaths
in classBaseShortestPathAlgorithm<V,E>
- Parameters:
source
- the source vertex- Returns:
- the shortest paths
- Throws:
NegativeCycleDetectedException
- in case a negative weight cycle is detected
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findPathBetween
public static <V,E> GraphPath<V,E> findPathBetween(Graph<V,E> graph, V source, V sink)
Find a path between two vertices.- Type Parameters:
V
- the graph vertex typeE
- the graph edge type- Parameters:
graph
- the graph to be searchedsource
- the vertex at which the path should startsink
- the vertex at which the path should end- Returns:
- a shortest path, or null if no path exists
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computeNegativeCycle
private GraphPath<V,E> computeNegativeCycle(E edge, java.util.Map<V,E> pred)
Computes a negative weight cycle assuming that the algorithm has already determined that it exists.- Parameters:
edge
- an edge which we know that belongs to the negative weight cyclepred
- the predecessor array- Returns:
- the negative weight cycle
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