如何在jgrapht DirectedAcyclicGraph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");

构建图后，如何得到所有根（没有入边的顶点）和所有叶（没有出边的顶点）的集合

Answer 1

以下是有效的，但我觉得不是最有效的。

// 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));

Answer 2

不应该是：

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

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

相反？

如何在jgrapht DirectedAcyclicGraph中找到根和叶集

How to find roots and leaves set in jgrapht DirectedAcyclicGraph

java

graph

jgrapht