kriegaex/jgrapht中CyclicTransitiveReduction报错：未找到哈密顿环(HC)

问题场景 #

测试JGraphT的CyclicTransitiveReduction类时，针对一个强连通有向图调用reduce()方法，抛出运行时异常，提示未找到哈密顿环，但该图实际为强连通图，按照算法逻辑应当存在哈密顿环。同时无法在kriegaex/jgrapht仓库找到提交Issue的入口。

测试代码 #

Graph<String, DefaultEdge> graph = GraphTypeBuilder
  .<String, DefaultEdge>directed()
  .allowingMultipleEdges(false)
  .allowingSelfLoops(false)
  .edgeClass(DefaultEdge.class)
  .buildGraph();

graph.addVertex("a");
graph.addVertex("b");
graph.addVertex("c");
graph.addVertex("d");
graph.addEdge("a", "b");
graph.addEdge("b", "c");
graph.addEdge("c", "a");
graph.addEdge("c", "d");
graph.addEdge("d", "b");

new CyclicTransitiveReduction<>(graph).reduce();

抛出的异常 #

java.lang.RuntimeException:
  No Hamiltonian cycle (HC) found.
  This should never happen and indicates an error in the algorithm,
  because the graph is strongly connected and a HC must therefore exist.

预期结果 #

执行CyclicTransitiveReduction.reduce()操作时不应抛出该异常。

内容的提问来源于stack exchange，提问作者sht