Библиотека Boost, как получить соседние узлы?

auto neighbours = boost::adjacent_vertices(94, g);

Распечатайте их, например,

for (auto vd : make_iterator_range(neighbours))
    std::cout << "94 has adjacent vertex " << vd << "\n";

Печать

94 has adjacent vertex 93
94 has adjacent vertex 3

Если вам нужны только исходящие края, это предполагает directedS или bidirectionalS, и в этом случае вы также можете сделать:

    for (auto ed : make_iterator_range(boost::out_edges(94, g)))
        std::cout << "outgoing: " << ed << "\n";
    for (auto ed : make_iterator_range(boost::in_edges(94, g)))
        std::cout << "incident: " << ed << "\n";

Живая демонстрация

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#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/connected_components.hpp>
#include <iostream>

using namespace boost;
using namespace std;

int main() {
    int N = 10000;

    struct status_t { typedef vertex_property_tag kind; };
    typedef property<status_t, string> status;
    typedef adjacency_list<vecS, vecS, bidirectionalS, status> MyGraph;

    MyGraph g(N);

    // add some random edges
    add_edge(0, 1, g);
    add_edge(100, 153, g);
    add_edge(634, 12, g);

    add_edge(93, 94, g);
    add_edge(94, 3, g);

    property_map<MyGraph, status_t>::type status_map = get(status_t(), g);

    for (int i = 0; i < 10; i++) {
        status_map[i] = "S";
    }

    {
        auto neighbours = boost::adjacent_vertices(94, g);
        for (auto vd : make_iterator_range(neighbours))
            std::cout << "94 has adjacent vertex " << vd << "\n";

        // prints
        // for undirected:
        //  94 has adjacent vertex 93
        //  94 has adjacent vertex 3
        // for directed/bidirectionalS:
        //  94 has adjacent vertex 3
    }

    {   // for bidirectionalS:
        for (auto ed : make_iterator_range(boost::out_edges(94, g)))
            std::cout << "outgoing: " << ed << "\n";
        for (auto ed : make_iterator_range(boost::in_edges(94, g)))
            std::cout << "incident: " << ed << "\n";
    }

}

Печать

94 has adjacent vertex 3
outgoing: (94,3)
incident: (93,94)