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/* Copyright (c) 1997-2015
Ewgenij Gawrilow, Michael Joswig (Technische Universitaet Berlin, Germany)
http://www.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.
--------------------------------------------------------------------------------
*/
#ifndef POLYMAKE_GRAPH_CONNECTED_H
#define POLYMAKE_GRAPH_CONNECTED_H
#include "polymake/graph/BFSiterator.h"
#include "polymake/PowerSet.h"
namespace polymake { namespace graph {
/// Determine whether a graph is connected.
template <typename Graph>
bool is_connected(const GenericGraph<Graph>& G)
{
if (!G.nodes()) return true;
BFSiterator<Graph> it(G.top(), nodes(G).front());
while (!it.at_end()) {
if (it.unvisited_nodes()==0) return true;
++it;
}
return false;
}
template <typename Graph>
class connected_components_iterator : protected BFSiterator< Graph, Visitor< BoolNodeVisitor<true> > > {
protected:
typedef BFSiterator< Graph, Visitor< BoolNodeVisitor<true> > > BFS;
Set<int> component;
void fill()
{
do {
component+=this->queue.front();
BFS::operator++();
} while (!BFS::at_end());
}
void next()
{
const int n=this->visitor.get_visited_nodes().front();
this->queue.push_back(n);
this->visitor.add(n);
--this->unvisited;
}
public:
typedef std::forward_iterator_tag iterator_category;
typedef Set<int> value_type;
typedef value_type reference;
typedef const value_type* pointer;
typedef ptrdiff_t difference_type;
typedef connected_components_iterator iterator;
typedef iterator const_iterator;
connected_components_iterator() {}
connected_components_iterator(const Graph& graph_arg)
: BFS(graph_arg, graph_arg.nodes() ? nodes(graph_arg).front() : -1)
{
if (this->unvisited>=0) fill();
}
reference operator* () const { return component; }
pointer operator-> () const { return &component; }
iterator& operator++ ()
{
component.clear();
if (BFS::unvisited>0) { next(); fill(); }
return *this;
}
const iterator operator++ (int) { iterator copy(*this); operator++(); return copy; }
bool operator== (const iterator& it) const { return component==it.component; }
bool operator!= (const iterator& it) const { return !operator==(it); }
bool at_end() const { return component.empty(); }
void rewind()
{
if (this->graph->nodes()) {
BFS::reset(nodes(*this->graph).front());
component.clear();
fill();
}
}
};
/// Compute the connected components
template <typename Graph> inline
pm::GraphComponents<const Graph&, connected_components_iterator>
connected_components(const GenericGraph<Graph>& G) { return G.top(); }
namespace {
template<typename Container, typename E>
void add_to(Container& C, const E& e)
{
C.push_back(e);
}
template<typename E>
void add_to(Set<E>& C, const E& e)
{
C += e;
}
} // end anonymous namespace
// compute a spanning tree rooted at vertex root_node,
// optionally restricted to a support set
template<typename GraphType, typename DirType, typename Container>
void
connected_component(const GenericGraph<GraphType, DirType>& G,
Container& C,
int root_node=0,
const Set<int> support=Set<int>())
{
std::list<int> unprocessed_leaves;
Bitset marked; // nodes already included in the tree
unprocessed_leaves.push_back(root_node); // we start the tree at the given node
add_to(C, root_node);
marked.insert(root_node);
while ( !unprocessed_leaves.empty() ) {
const int current = unprocessed_leaves.front();
unprocessed_leaves.pop_front();
const Set<int> neighbours = G.top().adjacent_nodes(current);
for (Entire< Set< int > >::const_iterator v = entire(neighbours); !v.at_end(); ++v)
if ((!support.size() || support.contains(*v))
&& !marked.contains(*v)) {
unprocessed_leaves.push_back(*v);
marked.insert(*v);
add_to(C, *v);
}
}
}
} }
namespace pm {
template <typename Graph>
struct check_iterator_feature< polymake::graph::connected_components_iterator<Graph>, end_sensitive > : True {};
template <typename Graph>
struct check_iterator_feature< polymake::graph::connected_components_iterator<Graph>, rewindable > : True {};
template <typename GraphRef>
class generic_of_GraphComponents<GraphRef, polymake::graph::connected_components_iterator>
: public GenericSet< GraphComponents<GraphRef,polymake::graph::connected_components_iterator>, Set<int>, operations::cmp > {};
}
#endif // POLYMAKE_GRAPH_CONNECTED_H
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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