拓扑排序

void Topsort(Graph G) {
    Queue Q;
    int Count = 0;
    Vertex V, W;
    Q = CreateQueue(NumVertex);
    MakeEmpty(Q);
    for each vertex Vertex
        if (Indegree[V] == 0)
            Enqueue(V, Q)

    while (!Empty(Q)) {
        V = Dequeue(Q);
        TopNum[V] = ++Count;

        for each W adjacent to V
            if (--Indegree[W] == 0)
                Enqueue(W, Q);
    }

    if (Counter != NumVertex)
        Error("cycle");

    DisposeQueue(Q);
}