Class BFSShortestPath<V,​E>

  • Type Parameters:
    V - the graph vertex type
    E - the graph edge type
    All Implemented Interfaces:
    ShortestPathAlgorithm<V,​E>

    public class BFSShortestPath<V,​E>
    extends java.lang.Object
    The BFS Shortest Path algorithm.

    An implementation of BFS shortest path algorithm to compute shortest paths from a single source vertex to all other vertices in an unweighted graph.

    The running time is $O(|V|+|E|)$.

    Author:
    Karri Sai Satish Kumar Reddy
    • Field Detail

      • GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE

        protected static final java.lang.String GRAPH_CONTAINS_A_NEGATIVE_WEIGHT_CYCLE
        Error message for reporting the existence of a negative-weight cycle.
        See Also:
        Constant Field Values
      • GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX

        protected static final java.lang.String GRAPH_MUST_CONTAIN_THE_SOURCE_VERTEX
        Error message for reporting that a source vertex is missing.
        See Also:
        Constant Field Values
      • GRAPH_MUST_CONTAIN_THE_SINK_VERTEX

        protected static final java.lang.String GRAPH_MUST_CONTAIN_THE_SINK_VERTEX
        Error message for reporting that a sink vertex is missing.
        See Also:
        Constant Field Values
      • graph

        protected final Graph<V,​E> graph
        The underlying graph.
    • Constructor Detail

      • BFSShortestPath

        public BFSShortestPath​(Graph<V,​E> graph)
        Construct a new instance.
        Parameters:
        graph - the input graph
    • Method Detail

      • 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 vertex
        sink - the target vertex
        Returns:
        a shortest path or null if no path exists
      • 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 type
        E - the graph edge type
        Parameters:
        graph - the graph to be searched
        source - the vertex at which the path should start
        sink - the vertex at which the path should end
        Returns:
        a shortest path, or null if no path exists
      • getPathWeight

        public double getPathWeight​(V source,
                                    V sink)
        Get the weight of the shortest path from a source vertex to a sink vertex. Returns Double.POSITIVE_INFINITY if no path exists.
        Specified by:
        getPathWeight in interface ShortestPathAlgorithm<V,​E>
        Parameters:
        source - the source vertex
        sink - 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
      • createEmptyPath

        protected final GraphPath<V,​E> createEmptyPath​(V source,
                                                             V sink)
        Create an empty path. Returns null if the source vertex is different than the target vertex.
        Parameters:
        source - the source vertex
        sink - the sink vertex
        Returns:
        an empty path or null null if the source vertex is different than the target vertex