我要打印所有顶点及其相邻的顶点。我在网上找到了一些有关如何执行此操作的示例,但对我而言不起作用。我收到错误消息,表示++运算符无法在AI上使用。我也认为它需要是vertex_idMap[*ai]而不是vertex_idMap[ai],但这会提示错误。有谁知道为什么这是错误的?

typedef adjacency_list<vecS, listS, directedS, VertexIDPorperty, EdgeWeight> Graph;  //the type of g
graph_traits <Graph>::vertex_iterator i, end;
graph_traits <Graph>::adjacency_iterator ai, a_end;
for (boost::tie(i, end) = vertices(g); i != end; ++i) {
    std::cout << vertex_idMap[*i];
    for (; ai != a_end; ++ai) {   //the ++ai seems to be wrong?
        std::cout << vertex_idMap[ai];
        if (boost::next(ai) != a_end)
            std::cout << ", ";
    }
std::cout << std::endl;

最佳答案

观察结果:

  • 其余代码在哪里?显然,这取决于所使用的类型。
  • aia_end未初始化(也许您实际上并不是说代码无法编译,这是您的全部问题)
  • vertex_idMap[ai]无法编译,因为vertex_iterator不是有效的vertex_descriptor

  • 这是一个固定的示例,其中包含想象中的缺失部分:

    Live On Coliru
    #include <boost/graph/adjacency_list.hpp>
    #include <iostream>
    
    using VertexIDPorperty = boost::property<boost::vertex_index_t, int>;
    using EdgeWeight       = boost::property<boost::edge_weight_t, double>;
    typedef boost::adjacency_list<boost::vecS, boost::listS, boost::directedS, VertexIDPorperty, EdgeWeight> Graph;
    
    Graph sample();
    
    int main() {
        Graph g = sample();
        auto vertex_idMap = get(boost::vertex_index, g);
        boost::graph_traits <Graph>::vertex_iterator i, end;
        boost::graph_traits <Graph>::adjacency_iterator ai, a_end;
    
        for (boost::tie(i, end) = vertices(g); i != end; ++i) {
            std::cout << vertex_idMap[*i] << ": ";
    
            for (boost::tie(ai, a_end) = adjacent_vertices(*i, g); ai != a_end; ++ai) {
                std::cout << vertex_idMap[*ai];
                if (boost::next(ai) != a_end)
                    std::cout << ", ";
            }
            std::cout << std::endl;
        }
    }
    

    实现sample()以创建随机图:
    #include <boost/graph/random.hpp>
    #include <random>
    
    Graph sample() {
        Graph g;
        std::mt19937 prng { std::random_device{}() };
    
        generate_random_graph(g, 10, 20, prng);
        int id = 0;
        for (auto vd : boost::make_iterator_range(vertices(g))) {
            put(boost::vertex_index, g, vd, ++id);
        }
    
        return g;
    }
    

    它打印如下内容:
    1: 9, 9, 4
    2: 6
    3:
    4:
    5: 9, 9, 8, 9
    6: 9, 3, 1
    7: 2, 10
    8: 6
    9: 8
    10: 7, 3, 8, 1, 4
    

    盒子外面

    打印图形可以更简单地完成:
    #include <boost/graph/graph_utility.hpp>
    // ...
    
    int main() {
        print_graph(sample());
    }
    

    Live On Coliru
    1 -->
    2 --> 3 10 9 6 6 10
    3 --> 8
    4 -->
    5 --> 4
    6 --> 1 5 8
    7 --> 4 9 2 2 1
    8 --> 6
    9 --> 5 7
    10 --> 7
    

    10-05 23:01
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