[英]My collection of maximal matched edges comes back empty (using QuickGraph in C#)
我正在尝试使用QuickGraph在我的二部图中找到最大匹配项,但是它们返回给我的MatchEdges集合为空。 我知道有匹配项,因为我用K7,7(完全二部图)测试了它。 因此,我对自己做错了感到困惑。
这是我的代码(出于可读性的考虑,我写了Vertex和Edge代替了实际的类):
public void findMatchings(List<Friend> setA, List<Friend> setB, List<Edge> candidateEdges) {
// we need a graph and two sets of vertices
IMutableVertexAndEdgeListGraph<Vertex, Edge> graph = new AdjacencyGraph<Vertex, Edge>();
foreach (Vertex vertex in setA) {
graph.AddVertex(vertex);
}
foreach (Vertex vertex in setB) {
graph.AddVertex(vertex);
}
foreach (Edge candidate in candidatesEdges) {
graph.AddEdge(candidate);
}
// sets a and b must be distinct, and their union must be equal to the set of all vertices in the graph
// (though they're conceptually the same set, to you or me, I created new instances of everything so they should be practically different.)
IEnumerable<Vertex> vertexSetA = setA;
IEnumerable<Vertex> vertexSetB = setB;
// These functions are used to create new vertices and edges during the execution of the algorithm.
// All added objects are removed before the computation returns
VertexFactory<Vertex> vertexFactory = newVertex; //newVertex() is defined below
EdgeFactory<Vertex, Edge> edgeFactory = (source, target) => new Edge(source, target);
// computing the maximum bipartite match
var maxMatch = new MaximumBipartiteMatchingAlgorithm<Vertex, Edge>(
graph, vertexSetA, vertexSetB, vertexFactory, edgeFactory);
Console.WriteLine(maxMatch.MatchedEdges.Count);
}
//This is in the same class as the above function:
static Vertex newVertex() {
return new Vertex("");
}
//This is the constructor in the Edge class:
public Edge(Vertex source, Vertex target) {
this.source = source;
this.target = target;
}
maxMatch.MatchedEdges.Count始终返回为0。这就是问题所在。
我希望对此有一个简单的解决方案,例如我不应该使用新的AdjacencyGraph()之类的东西,但是我也乐于接受其他建议在二部图中找到最大匹配项的建议。
谢谢!
顺便说一句,这个链接是我用来写东西的: QuickGraph中的最大二分匹配
创建MaximumBipartiteMatchingAlgorithm
实例后,您需要调用其Compute方法,以便计算匹配。 就您的示例而言,这意味着添加:
maxMatch.Compute();
同样,对newVertex()
方法的每次调用都应返回一个唯一的字符串,该字符串不同于标识MaximumBipartiteMatchingAlgorithm
的输入中的顶点的字符串。
仅供参考:我个人发现,有时maxMatch.MatchedEdges
包含太多的边:有些顶点被覆盖两次。 另外,我还看到maxMatch.MatchedEdges
包含的边不在MaximumBipartiteMatchingAlgorithm的输入中,而是由算法在内部创建。
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