c++ - 使用 BFS 在 Boost BGL 图中查找所有可达的顶点

Question

我构建了一个 boost BGL 图:

using vertex_t = std::variant<node_t, specialNode_t>; // structs
using edge_t = std::variant<TerminalType>;            // enum

using Graph_t = boost::adjacency_list<
    boost::vecS,
    boost::vecS,
    boost::undirectedS,
    vertex_t,
    edge_t>;

Graph_t myGraph;

我正在尝试查找(收集)从某个起点(顶点)可到达的所有顶点(按距离排序)。这意味着我想创建一个可从某个起始顶点到达的所有顶点的列表，其中“更近”的顶点存储在列表/vector 的前面。因此我(认为我)需要 BFS。

不幸的是，我没有找到如何在没有编译错误的情况下做到这一点:

boost::queue<vertex_t> Q;
boost::default_bfs_visitor vis; // Will do my collecting visitor later...

auto indexmap = boost::get(boost::vertex_index, myGraph);
auto colormap = boost::make_vector_property_map<boost::default_color_type>(indexmap);

boost::breadth_first_visit(myGraph, start, std::ref(Q), vis, colormap);

这会导致以下错误:

Error   C2039   'push': is not a member of 'std::reference_wrapper<boost::queue<ListSim::vertex_t,std::deque<_Tp,std::allocator<_Ty>>>>'
Error   C2039   'empty': is not a member of 'std::reference_wrapper<boost::queue<ListSim::vertex_t,std::deque<_Tp,std::allocator<_Ty>>>>'
Error   C2039   'top': is not a member of 'std::reference_wrapper<boost::queue<ListSim::vertex_t,std::deque<_Tp,std::allocator<_Ty>>>>'
Error   C2039   'pop': is not a member of 'std::reference_wrapper<boost::queue<ListSim::vertex_t,std::deque<_Tp,std::allocator<_Ty>>>>'
Error   C2039   'push': is not a member of 'std::reference_wrapper<boost::queue<ListSim::vertex_t,std::deque<_Tp,std::allocator<_Ty>>>>'

我的问题:

1. 任何人都可以阐明我的错误吗？或者指向一个例子？
2. 是否有更好的(在效率方面)或不同的方法来实现该目标？

(我想先使用“connected_components”...但它使用的 DFS 无法满足我的距离/排序标准)。

Answer 1

文档说 Buffer 需要是一个 vertex_descriptors 队列。您不小心将其声明为具有 vertex_t(顶点属性包)作为值类型。

修复它:

using vertex_descriptor = boost::graph_traits<Graph_t>::vertex_descriptor;

boost::queue<vertex_descriptor> Q;

然后编译:

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#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/breadth_first_search.hpp>
#include <variant>
#include <queue>

struct node_t {
};
struct specialNode_t {
};
enum class TerminalType {
};

using vertex_t = std::variant<node_t, specialNode_t>; // structs
using edge_t = std::variant<TerminalType>;            // enum

using Graph_t = boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, vertex_t, edge_t>;

int main() {
    Graph_t myGraph(5);
    boost::default_bfs_visitor vis; // Will do my collecting visitor later...

    auto indexmap = boost::get(boost::vertex_index, myGraph);
    auto colormap = boost::make_vector_property_map<boost::default_color_type>(indexmap);

    using vertex_descriptor = boost::graph_traits<Graph_t>::vertex_descriptor;

    boost::queue<vertex_descriptor> Q;
    boost::breadth_first_visit(myGraph, 0, Q, vis, colormap);
}