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/*
Copyright (C) 2006 Pedro Felzenszwalb
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 for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef DISJOINT_SET
#define DISJOINT_SET
// disjoint-set forests using union-by-rank and path compression (sort of).
typedef struct {
int rank;
int p;
int size;
} uni_elt;
class universe {
public:
universe(int elements);
~universe();
int find(int x);
void join(int x, int y);
int size(int x) const { return elts[x].size; }
int num_sets() const { return num; }
private:
uni_elt *elts;
int num;
};
universe::universe(int elements) {
elts = new uni_elt[elements];
num = elements;
for (int i = 0; i < elements; i++) {
elts[i].rank = 0;
elts[i].size = 1;
elts[i].p = i;
}
}
universe::~universe() {
delete [] elts;
}
int universe::find(int x) {
int y = x;
while (y != elts[y].p)
y = elts[y].p;
elts[x].p = y;
return y;
}
void universe::join(int x, int y) {
if (elts[x].rank > elts[y].rank) {
elts[y].p = x;
elts[x].size += elts[y].size;
} else {
elts[x].p = y;
elts[y].size += elts[x].size;
if (elts[x].rank == elts[y].rank)
elts[y].rank++;
}
num--;
}
#endif
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