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/****************************************************************************
* VCGLib o o *
* Visual and Computer Graphics Library o o *
* _ O _ *
* Copyright(C) 2004 \/)\/ *
* Visual Computing Lab /\/| *
* ISTI - Italian National Research Council | *
* \ *
* All rights reserved. *
* *
* 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 of the License, or *
* (at your option) any later version. *
* *
* 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 (http://www.gnu.org/licenses/gpl.txt) *
* for more details. *
* *
****************************************************************************/
#ifndef VCG_MATH_UNIONSET_H
#define VCG_MATH_UNIONSET_H
// some stuff for portable hashes...
#ifdef WIN32
#ifndef __MINGW32__
#include <hash_map>
#include <hash_set>
#define STDEXT stdext
#else
#include <ext/hash_map>
#include <ext/hash_set>
#define STDEXT __gnu_cxx
#endif
#else
#include <ext/hash_map>
#include <ext/hash_set>
#define STDEXT __gnu_cxx
// It's terrible but gnu's hash_map needs an instantiation of hash() for
// every key type! So we cast the pointer to void*
namespace __gnu_cxx
{
template <> class hash<void *>: private hash<unsigned long>
{
public:
size_t operator()(const void *ptr) const { return hash<unsigned long>::operator()((unsigned long)ptr); }
};
}
#endif
#include <vector>
#include <assert.h>
namespace vcg
{
/*!
* Given a set of elements, it is often useful to break them up or partition them into a number of separate, nonoverlapping groups.
* A disjoint-set data structure is a data structure that keeps track of such a partitioning. See
* <a href="http://en.wikipedia.org/wiki/Disjoint-set_data_structure">Diskoint-set data structure on Wikipedia </a> for more details.
*/
template<class OBJECT_TYPE>
class DisjointSet
{
/*************************************************
* Inner class definitions
**************************************************/
struct DisjointSetNode
{
DisjointSetNode(OBJECT_TYPE *x) {obj=x; parent=obj; rank=0;}
OBJECT_TYPE *obj;
OBJECT_TYPE *parent;
int rank;
};
typedef OBJECT_TYPE* ObjectPointer;
typedef std::pair< ObjectPointer, int > hPair;
struct SimpleObjHashFunc{
inline size_t operator ()(const ObjectPointer &p) const {return size_t(p);}
};
#ifdef _MSC_VER
STDEXT::hash_map< OBJECT_TYPE*, int > inserted_objects;
typedef typename STDEXT::hash_map< ObjectPointer, int >::iterator hIterator;
#else
STDEXT::hash_map< OBJECT_TYPE*, int, SimpleObjHashFunc > inserted_objects;
typedef typename STDEXT::hash_map< ObjectPointer, int, SimpleObjHashFunc >::iterator hIterator;
#endif
typedef std::pair< hIterator, bool > hInsertResult;
public:
/*!
* Default constructor
*/
DisjointSet() {}
/*!
* Makes a group containing only a given element (a singleton).
*/
void MakeSet(OBJECT_TYPE *x)
{
int object_count = int(inserted_objects.size());
assert(inserted_objects.find(x)==inserted_objects.end()); //the map mustn't already contain the object x
nodes.push_back(DisjointSetNode(x));
inserted_objects.insert( hPair(x,object_count) );
}
/*!
* Combine or merge two groups into a single group.
*/
void Union(OBJECT_TYPE *x, OBJECT_TYPE *y)
{
OBJECT_TYPE *s0 = FindSet(x);
OBJECT_TYPE *s1 = FindSet(y);
Link(s0, s1);
}
/*!
* Determine which group a particular element is in.
*/
OBJECT_TYPE* FindSet(OBJECT_TYPE *x)
{
hIterator pos = inserted_objects.find(x);
assert(pos!=inserted_objects.end());
DisjointSetNode *node = &nodes[pos->second];
if (node->parent!=x)
node->parent = FindSet(node->parent);
return node->parent;
}
private:
/*
*/
void Link(OBJECT_TYPE *x, OBJECT_TYPE *y)
{
hIterator xPos = inserted_objects.find(x);
hIterator yPos = inserted_objects.find(y);
assert(xPos!=inserted_objects.end() && yPos!=inserted_objects.end());
DisjointSetNode *xNode = &nodes[xPos->second];
DisjointSetNode *yNode = &nodes[yPos->second];
if (xNode->rank>yNode->rank)
xNode->parent = y;
else
{
yNode->parent = x;
if (xNode->rank==yNode->rank)
yNode->rank++;
}
}
protected:
std::vector< DisjointSetNode > nodes;
};
};// end of namespace vcg
#endif //VCG_MATH_UNIONSET_H
|
