Package org.jgrapht.alg.shortestpath

Class KShortestSimplePaths<V,​E>

  • Type Parameters:
    V - the graph vertex type
    E - the graph edge type
    All Implemented Interfaces:
    KShortestPathAlgorithm<V,​E>
    public class KShortestSimplePaths<V,​E>
extends Object
implements KShortestPathAlgorithm<V,​E>
    The algorithm determines the k shortest simple paths in increasing order of weight. Weights can be negative (but no negative cycle is allowed), and paths can be constrained by a maximum number of edges. Graphs with multiple (parallel) edges are allowed.

    The algorithm is a variant of the Bellman-Ford algorithm but instead of only storing the best path it stores the "k" best paths at each pass, yielding a complexity of $O(k \cdot n \cdot (m^2))$ where $m$ is the number of edges and $n$ is the number of vertices.

    • Constructor Detail

      • KShortestSimplePaths

        public KShortestSimplePaths​(Graph<V,​E> graph)
        Constructs an object to compute ranking shortest paths in a graph.
        Parameters:
        graph - graph on which shortest paths are searched

      • KShortestSimplePaths

        public KShortestSimplePaths​(Graph<V,​E> graph,
                            PathValidator<V,​E> pathValidator)
        Constructs an object to compute ranking shortest paths in a graph. A non-null path validator may be used to accept/deny paths according to some external logic. These validations will be used in addition to the basic path validations which are that the path is from start to target with no loops.
        Parameters:
        graph - graph on which shortest paths are searched.
        pathValidator - the path validator to use

      • KShortestSimplePaths

        public KShortestSimplePaths​(Graph<V,​E> graph,
                            int nMaxHops)
        Constructs an object to calculate ranking shortest paths in a graph.
        Parameters:
        graph - graph on which shortest paths are searched
        nMaxHops - maximum number of edges of the calculated paths
        Throws:
        IllegalArgumentException - if nMaxHops is negative or 0.

      • KShortestSimplePaths

        public KShortestSimplePaths​(Graph<V,​E> graph,
                            int nMaxHops,
                            PathValidator<V,​E> pathValidator)
        Constructs an object to calculate ranking shortest paths in a graph. A non-null path validator may be used to accept/deny paths according to some external logic. These validations will be used in addition to the basic path validations which are that the path is from start to target with no loops.
        Parameters:
        graph - graph on which shortest paths are searched
        nMaxHops - maximum number of edges of the calculated paths
        pathValidator - the path validator to use
        Throws:
        IllegalArgumentException - if nMaxHops is negative or 0.

    • Method Detail

      • getPaths

        public List<GraphPath<V,​E>> getPaths​(V startVertex,
                                           V endVertex,
                                           int k)
        Returns a list of the $k$ shortest simple paths in increasing order of weight.
        Specified by:
        getPaths in interface KShortestPathAlgorithm<V,​E>
        Parameters:
        startVertex - source vertex of the calculated paths.
        endVertex - target vertex of the calculated paths.
        k - the number of shortest paths to return
        Returns:
        an iterator of paths between the start vertex and the end vertex
        Throws:
        IllegalArgumentException - if the graph does not contain the startVertex or the endVertex
        IllegalArgumentException - if the startVertex and the endVertex are the same vertices
        IllegalArgumentException - if k is negative or zero