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#ifndef BLISS_ORBIT_HH
#define BLISS_ORBIT_HH
/*
Copyright (c) 2006-2011 Tommi Junttila
Released under the GNU General Public License version 3.
This file is part of bliss.
bliss is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License version 3
as published by the Free Software Foundation.
bliss 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.
You should have received a copy of the GNU General Public License
along with Foobar. If not, see <http://www.gnu.org/licenses/>.
*/
namespace bliss {
/** \internal
* \brief A class for representing orbit information.
*
* Given a set {0,...,N-1} of N elements, represent equivalence
* classes (that is, unordered partitions) of the elements.
* Supports only equivalence class merging, not splitting.
* Merging two classes requires time O(k), where k is the number of
* the elements in the smaller of the merged classes.
* Getting the smallest representative in a class (and thus testing
* whether two elements belong to the same class) is a constant time operation.
*/
class Orbit
{
class OrbitEntry
{
public:
unsigned int element;
OrbitEntry *next;
unsigned int size;
};
OrbitEntry *orbits;
OrbitEntry **in_orbit;
unsigned int nof_elements;
unsigned int _nof_orbits;
void merge_orbits(OrbitEntry *o1, OrbitEntry *o2);
public:
/**
* Create a new orbit information object.
* The init() function must be called next to actually initialize
* the object.
*/
Orbit();
~Orbit();
/**
* Initialize the orbit information to consider sets of \a N elements.
* It is required that \a N > 0.
* The orbit information is reset so that each element forms
* an orbit of its own.
* Time complexity is O(N).
* \sa reset()
*/
void init(const unsigned int N);
/**
* Reset the orbits so that each element forms an orbit of its own.
* Time complexity is O(N).
*/
void reset();
/**
* Merge the orbits of the elements \a e1 and \a e2.
* Time complexity is O(k), where k is the number of elements in
* the smaller of the merged orbits.
*/
void merge_orbits(unsigned int e1, unsigned int e2);
/**
* Is the element \a e the smallest element in its orbit?
* Time complexity is O(1).
*/
bool is_minimal_representative(unsigned int e) const;
/**
* Get the smallest element in the orbit of the element \a e.
* Time complexity is O(1).
*/
unsigned int get_minimal_representative(unsigned int e) const;
/**
* Get the number of elements in the orbit of the element \a e.
* Time complexity is O(1).
*/
unsigned int orbit_size(unsigned int e) const;
/**
* Get the number of orbits.
* Time complexity is O(1).
*/
unsigned int nof_orbits() const {return _nof_orbits; }
};
} // namespace bliss
#endif
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