| /* | |
| 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 | |
| */ | |
| // 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--; | |
| } | |