java.lang.Object
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 $O(|E||V|)$.
- Author:
- Dimitrios Michail
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Nested Class Summary
Nested classes/interfaces inherited from interface org.jgrapht.alg.interfaces.ShortestPathAlgorithm
ShortestPathAlgorithm.SingleSourcePaths<V,
E> -
Field Summary
Modifier and TypeFieldDescriptionprotected final Comparator<Double>
The underlying graph.protected static final String
Error message for reporting the existence of a negative-weight cycle.protected static final String
Error message for reporting that a sink vertex is missing.protected static final String
Error message for reporting that a source vertex is missing.protected final int
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Constructor Summary
ConstructorDescriptionBellmanFordShortestPath
(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 TypeMethodDescriptioncreateEmptyPath
(V source, V sink) Create an empty path.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.double
getPathWeight
(V source, V sink) Get the weight of the shortest path from a source vertex to a sink vertex.
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Field Details
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comparator
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maxHops
protected final int maxHops -
GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE
Error message for reporting the existence of a negative-weight cycle.- See Also:
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GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
Error message for reporting that a source vertex is missing.- See Also:
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GRAPH_MUST_CONTAIN_THE_SINK_VERTEX
Error message for reporting that a sink vertex is missing.- See Also:
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graph
The underlying graph.
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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> - 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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getPathWeight
Get the weight of the shortest path from a source vertex to a sink vertex. ReturnsDouble.POSITIVE_INFINITY
if no path exists.- Specified by:
getPathWeight
in interfaceShortestPathAlgorithm<V,
E> - Parameters:
source
- the source vertexsink
- the sink vertex- Returns:
- the weight of the shortest path from a source vertex to a sink vertex, or
Double.POSITIVE_INFINITY
if no path exists
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createEmptyPath
Create an empty path. Returns null if the source vertex is different than the target vertex.- Parameters:
source
- the source vertexsink
- the sink vertex- Returns:
- an empty path or null null if the source vertex is different than the target vertex
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