java - 如何在jgrapht DirectedAcyclingGraph中找到根和叶集

Question

我的代码:

import org.jgrapht.graph.DirectedAcyclicGraph;
// ...
private DirectedAcyclicGraph<String, DefaultEdge> graph = new DirectedAcyclicGraph<>(DefaultEdge.class);
// ...
graph.addVertex("x");
graph.addVertex("y");
// ...
graph.addEdge("x", "y");

构造图后，如何获得所有根(没有传入边的顶点)和所有叶子(没有传出边的顶点)的集合

Answer 1

以下内容有效，但我认为并不是最有效的。

// leaves:
graph.vertexSet().stream()
                .filter(key -> graph.outgoingEdgesOf(key).size() == 0)
                .forEach(key -> doLeavesStuff(key));

// roots:
graph.vertexSet().stream()
                .filter(key -> graph.incomingEdgesOf(key).size() == 0)
                .forEach(key -> doRootsStuff(key));