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// Copyright (C) 2002 Graydon Hoare <graydon@pobox.com>
//
// This program is made available under the GNU GPL version 2.0 or
// greater. See the accompanying file COPYING for details.
//
// This program is distributed WITHOUT ANY WARRANTY; without even the
// implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE.
#ifndef __CYCLE_DETECTOR_HH__
#define __CYCLE_DETECTOR_HH__
#include "vector.hh"
#include <stack>
#include <set>
#include "quick_alloc.hh"
#include "sanity.hh"
template <typename T>
struct cycle_detector
{
typedef std::vector< T > edge_vec;
typedef std::vector <edge_vec > edge_map;
typedef std::pair <typename edge_vec::const_iterator,
typename edge_vec::const_iterator> state;
typedef std::stack <state > edge_stack;
edge_map edges;
edge_stack stk;
std::set<T> global_in_edges;
void put_edge (T const & src, T const & dst)
{
if (src >= edges.size())
edges.resize(src + 1);
edge_vec & src_edges = edges.at(src);
for (typename edge_vec::const_iterator i = src_edges.begin();
i != src_edges.end(); ++i)
if (*i == dst)
return;
src_edges.push_back(dst);
global_in_edges.insert(dst);
}
bool edge_makes_cycle(T const & src, T const & dst)
{
if (src == dst)
return true;
if (dst >= edges.size() || edges.at(dst).empty())
return false;
if (global_in_edges.find(src) == global_in_edges.end())
return false;
while (!stk.empty())
stk.pop();
stk.push(make_pair(edges.at(dst).begin(),
edges.at(dst).end()));
std::set<T> visited;
while (!stk.empty())
{
bool pushed = false;
for (state & curr = stk.top(); curr.first != curr.second && !pushed; ++curr.first)
{
T val = *(curr.first);
if (val == src)
{
return true;
}
if (val < edges.size() && ! edges.at(val).empty()
&& visited.find(val) == visited.end())
{
visited.insert(val);
stk.push(make_pair(edges.at(val).begin(),
edges.at(val).end()));
pushed = true;
}
}
if (!pushed)
stk.pop();
}
return false;
}
};
#endif // __CYCLE_DETECTOR_HH__
// Local Variables:
// mode: C++
// fill-column: 76
// c-file-style: "gnu"
// indent-tabs-mode: nil
// End:
// vim: et:sw=2:sts=2:ts=2:cino=>2s,{s,\:s,+s,t0,g0,^-2,e-2,n-2,p2s,(0,=s:
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