java.lang.Object
org.jgrapht.alg.shortestpath.BaseShortestPathAlgorithm<V,E>
org.jgrapht.alg.shortestpath.BellmanFordShortestPath<V,E>
- Type Parameters:
V
- the graph vertex typeE
- the graph edge type
- All Implemented Interfaces:
ShortestPathAlgorithm<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
Nested classes/interfaces inherited from interface org.jgrapht.alg.interfaces.ShortestPathAlgorithm
ShortestPathAlgorithm.SingleSourcePaths<V,
E> -
Field Summary
FieldsFields 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
ConstructorsConstructorDescriptionBellmanFordShortestPath
(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. -
Method Summary
Modifier and TypeMethodDescriptioncomputeNegativeCycle
(E edge, 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.Get a shortest path from a source vertex to a sink vertex.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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Field Details
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comparator
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maxHops
protected final int maxHops
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Constructor Details
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BellmanFordShortestPath
Construct a new instance.- Parameters:
graph
- the input graph
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BellmanFordShortestPath
Construct a new instance.- Parameters:
graph
- the input graphepsilon
- tolerance when comparing floating point values
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BellmanFordShortestPath
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:
IllegalArgumentException
- if the number of maxHops is not positive
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Method Details
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getPath
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
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
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
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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