使用 Boost Graph 库查找连接的组件，顶点和边类型为 boost::listS答案

【问题标题】：Find connected components using Boost Graph library, with the vertex and edge type being boost::listS使用 Boost Graph 库查找连接的组件，顶点和边类型为 boost::listS
【发布时间】：2017-12-20 15:41:56
【问题描述】：

我正在尝试在无向图中查找连接的组件。该图由boost::adjacency_list 表示。对于我的应用程序，顶点和边的类型必须是boost::listS。我尝试了以下代码，但无法编译。但是，如果我将顶点和边类型更改为boost::vecS，代码就可以正常工作。关于如何修复代码的任何想法？

#include <iostream>
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/connected_components.hpp>
typedef boost::adjacency_list<boost::listS,boost::listS,boost::undirectedS> Cluster;
int main() {
    using namespace boost;
    Cluster A;
    add_vertex(A);
    add_vertex(A);
    add_vertex(A);
    add_vertex(A); // add 4 vertex to the graph

    for (int i=0; i<2; i++){
        for (int j=(i+1); j<3; j++){
            std::cout<<i<<"  "<<j<<"\n";
            add_edge(vertex(i,A), vertex(j,A), A);
        }
    } // add edge between 0-1, 0-2, 1-2.

    std::vector<int> subclusters(num_vertices(A));
    int nclusters=boost::connected_components(A, &subclusters[0]); // find the connected components
}

【问题讨论】：

标签： c++ boost graph

【解决方案1】：

docs say¹ 组件映射需要使用键 vertex_descriptor 对可写属性映射进行建模，并将组件 ID 存储为值。

您可能应该将make_assoc_property_map 与地图一起使用：

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std::map<Cluster::vertex_descriptor, int> subclusters;
int nclusters = boost::connected_components(A, boost::make_assoc_property_map(subclusters)); // find the connected components


for (auto& p : subclusters) {
    std::cout << "Vertex " << boost::get(boost::vertex_index, A, p.first) << " is in cluster " << p.second << "\n";
}

打印：

0 -- 1
0 -- 2
1 -- 2
Vertex 0 is in cluster 0
Vertex 1 is in cluster 0
Vertex 2 is in cluster 0
Vertex 3 is in cluster 1

但我想要一个向量

如果您坚持，您仍然可以使用向量，但您必须提供从顶点描述符到完整顶点 id 的映射：

typedef boost::adjacency_list<
        boost::listS,
        boost::listS,
        boost::undirectedS,
        boost::property<boost::vertex_index_t, int>
    > Cluster;

现在，您也必须填写该属性：

Cluster A;
add_vertex(0, A);
add_vertex(1, A);
add_vertex(2, A);
add_vertex(3, A);

然后你必须改用make_iterator_property_map，为间接提供一个顶点索引属性映射：

std::vector<int> subclusters(4);
auto comp_map = make_iterator_property_map(subclusters.begin(), get(boost::vertex_index, A));
int nclusters = connected_components(A, comp_map); // find the connected components

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

typedef boost::adjacency_list<
        boost::listS,
        boost::listS,
        boost::undirectedS,
        boost::property<boost::vertex_index_t, int>
    > Cluster;

int main() {
    Cluster A;
    add_vertex(0, A);
    add_vertex(1, A);
    add_vertex(2, A);
    add_vertex(3, A);

    for (int i = 0; i < 2; i++) {
        for (int j = (i + 1); j < 3; j++) {
            std::cout << i << " -- " << j << "\n";
            add_edge(vertex(i, A), vertex(j, A), A);
        }
    } // add edge between 0-1, 0-2, 1-2.

    // NOTE: 4, not "num_vertices", but enough to accomodate the highest value
    // of the `vertex_index` property
    std::vector<int> subclusters(4);
    auto comp_map = make_iterator_property_map(subclusters.begin(), get(boost::vertex_index, A));
    int nclusters = connected_components(A, comp_map); // find the connected components

    for (size_t id = 0; id < subclusters.size(); ++id) {
        std::cout << "Vertex id " << id << " is in cluster " << subclusters.at(id) << "\n";
    }
}

打印

0 -- 1
0 -- 2
1 -- 2
Vertex id 0 is in cluster 0
Vertex id 1 is in cluster 0
Vertex id 2 is in cluster 0
Vertex id 3 is in cluster 1

【讨论】：

完美运行！非常感谢。