[英]How do I change the edge weight in a graph using the Boost Graph Library?
我使用Boost圖庫定義了一個Graph,
typedef boost::property<boost::edge_weight_t, int> EdgeWeightProperty;
typedef boost::adjacency_list<boost::listS, boost::vecS,boost::undirectedS,boost::no_property,EdgeWeightProperty> Graph;
使用添加邊緣相當簡單
boost::add_edge(vertice1, vertice2, weight, graph);
我還沒有弄清楚如何設置邊緣重量。 一種可能的解決方案是刪除邊緣並使用更新的權重值重新添加它,但是,這看起來有點過分。
一種解決方案是執行以下操作
typedef boost::adjacency_list<boost::setS, boost::vecS, boost::undirectedS,boost::no_property,EdgeWeightProperty> Graph;
typedef Graph::edge_descriptor Edge;
Graph g;
std::pair<Edge, bool> ed = boost::edge(v1,v2,g);
int weight = get(boost::edge_weight_t(), g, ed.first);
int weightToAdd = 10;
boost::put(boost::edge_weight_t(), g, ed.first, weight+weightToAdd);
另一種解決方案是使用屬性映射。 這是一個例子。
// Edge weight.
typedef boost::property<boost::edge_weight_t, int> EdgeWeightProperty;
// Graph.
typedef boost::adjacency_list< boost::listS,
boost::vecS,
boost::undirectedS,
boost::no_property,
EdgeWeightProperty > Graph;
// Vertex descriptor.
typedef typename boost::graph_traits<Graph>::vertex_descriptor Vertex;
// The Graph object
Graph g;
// Populates the graph.
Vertex v1 = boost::add_vertex(g);
Vertex v2 = boost::add_vertex(g);
Vertex v3 = boost::add_vertex(g);
boost::add_edge(v1, v2, EdgeWeightProperty(2), g);
boost::add_edge(v1, v3, EdgeWeightProperty(4), g);
boost::add_edge(v2, v3, EdgeWeightProperty(5), g);
// The property map associated with the weights.
boost::property_map < Graph,
boost::edge_weight_t >::type EdgeWeightMap = get(boost::edge_weight, g);
// Loops over all edges and add 10 to their weight.
boost::graph_traits< Graph >::edge_iterator e_it, e_end;
for(std::tie(e_it, e_end) = boost::edges(g); e_it != e_end; ++e_it)
{
EdgeWeightMap[*e_it] += 10;
}
// Prints the weighted edgelist.
for(std::tie(e_it, e_end) = boost::edges(g); e_it != e_end; ++e_it)
{
std::cout << boost::source(*e_it, g) << " "
<< boost::target(*e_it, g) << " "
<< EdgeWeightMap[*e_it] << std::endl;
}
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