1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/****************************************************************************
* VCGLib o o *
* Visual and Computer Graphics Library o o *
* _ O _ *
* Copyright(C) 2004-2016 \/)\/ *
* 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
#include <unordered_map>
#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);}
};
std::unordered_map< OBJECT_TYPE*, int > inserted_objects;
typedef typename std::unordered_map< OBJECT_TYPE*, int >::iterator hIterator;
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
|
