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ng_undirected: avoid parallel edge at construction

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(Rather than using setS for out edges)
This commit is contained in:
Justin Viiret 2017-03-21 12:37:52 +11:00 committed by Matthew Barr
parent 9724f8c3cc
commit 4b3ff085d3
1 changed files with 17 additions and 5 deletions
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18
src/nfagraph/ng_undirected.h
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@ -52,11 +52,11 @@ namespace ue2 {
* of parallel edges. The only vertex property constructed is \a
* vertex_index_t.
*/
using NFAUndirectedGraph =
boost::adjacency_list<boost::setS, // out edges
using NFAUndirectedGraph = boost::adjacency_list<
boost::listS, // out edges
boost::listS, // vertices
boost::undirectedS, // graph is undirected
boost::property<boost::vertex_index_t, size_t>>;
boost::property<boost::vertex_index_t, size_t>>; // vertex properties
using NFAUndirectedVertex = NFAUndirectedGraph::vertex_descriptor;
@ -95,6 +95,14 @@ NFAUndirectedGraph createUnGraph(const Graph &g,
boost::put(boost::vertex_index, ug, nuv, idx++);
}
// Track seen edges so that we don't insert parallel edges.
using Vertex = typename Graph::vertex_descriptor;
unordered_set<std::pair<Vertex, Vertex>> seen;
seen.reserve(num_edges(g));
auto make_ordered_edge = [](Vertex a, Vertex b) {
return std::make_pair(std::min(a, b), std::max(a, b));
};
for (const auto &e : ue2::edges_range(g)) {
auto u = source(e, g);
auto v = target(e, g);
@ -109,6 +117,10 @@ NFAUndirectedGraph createUnGraph(const Graph &g,
continue;
}
if (!seen.emplace(make_ordered_edge(u, v)).second) {
continue; // skip parallel edge.
}
NFAUndirectedVertex new_u = old2new.at(u);
NFAUndirectedVertex new_v = old2new.at(v);