| /* |
| 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: |
| explicit 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 |