DAG图中得到顶点的所有上下游顶点集合

在DAG图中得到顶点的所有上下游顶点集合，这个在jgrapht中DirectedAcyclicGraph.java有具体实现。

把它的源代码放在这里，就是为了学习一下API。

/**
 * Get the ancestors of a vertex.
 *
 * @param vertex the vertex to get the ancestors of
 * @return {@link Set} of ancestors of a vertex
 */
public Set<V> getAncestors(V vertex)
{
    EdgeReversedGraph<V, E> reversedGraph = new EdgeReversedGraph<>(this);
    Iterator<V> iterator = new DepthFirstIterator<>(reversedGraph, vertex);
    Set<V> ancestors = new HashSet<>();

    // Do not add start vertex to result.
    if (iterator.hasNext()) {
        iterator.next();
    }

    iterator.forEachRemaining(ancestors::add);

    return ancestors;
}

/**
 * Get the descendants of a vertex.
 *
 * @param vertex the vertex to get the descendants of
 * @return {@link Set} of descendants of a vertex
 */
public Set<V> getDescendants(V vertex)
{
    Iterator<V> iterator = new DepthFirstIterator<>(this, vertex);
    Set<V> descendants = new HashSet<>();

    // Do not add start vertex to result.
    if (iterator.hasNext()) {
        iterator.next();
    }

    iterator.forEachRemaining(descendants::add);

    return descendants;
}

 

 

    public static void test032() throws Exception {
        DirectedAcyclicGraph<String, GoodEdge> dag = new DirectedAcyclicGraph<>(GoodEdge.class);
        dag.addVertex("A");
        dag.addVertex("B");
        dag.addVertex("C");
        dag.addVertex("D");
        dag.addVertex("E");
        dag.addVertex("F");

        dag.addEdge("A", "B");
        dag.addEdge("A", "C");
        dag.addEdge("B", "D");
        dag.addEdge("B", "E");
        dag.addEdge("C", "D");
        dag.addEdge("D", "F");
        dag.addEdge("E", "F");

        dag.edgeSet().forEach(e -> {
            System.out.println(String.format("%s->%s", e.getSource(), e.getTarget()));
        });

        System.out.println(dag.getAncestors("F"));// [A, B, C, D, E]
        System.out.println(dag.getDescendants("B"));// [D, E, F]
    }