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/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
*/
#pragma once
#include "polymake/Graph.h"
namespace polymake { namespace graph {
namespace {
template <typename in_edge_iterator, typename out_edge_iterator>
bool stop_at(const in_edge_iterator&, const out_edge_iterator& out_edge_it, Directed)
{
return out_edge_it.at_end();
}
template <typename edge_iterator>
bool stop_at(const edge_iterator& edge1_it, const edge_iterator& edge2_it, Undirected)
{
return edge1_it == edge2_it;
}
}
template <typename Kind>
Graph<typename Kind::non_multi_type> line_graph(const Graph<Kind>& G)
{
G.enumerate_edges();
Graph<typename Kind::non_multi_type> result(G.edges());
for (auto node_it = nodes(G).begin(); !node_it.at_end(); ++node_it) {
for (auto in_edge_it = G.in_edges(*node_it).begin(); !in_edge_it.at_end(); ++in_edge_it) {
for (auto out_edge_it = G.out_edges(*node_it).begin();
!stop_at(in_edge_it, out_edge_it, typename Kind::non_multi_type());
++out_edge_it) {
result.edge(*in_edge_it, *out_edge_it);
}
}
}
return result;
}
} }
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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