[37] | 1 | /* |
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| 2 | Copyright (C) 2006 Pedro Felzenszwalb |
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| 3 | |
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| 4 | This program is free software; you can redistribute it and/or modify |
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| 5 | it under the terms of the GNU General Public License as published by |
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| 6 | the Free Software Foundation; either version 2 of the License, or |
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| 7 | (at your option) any later version. |
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| 8 | |
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| 9 | This program is distributed in the hope that it will be useful, |
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 12 | GNU General Public License for more details. |
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| 13 | |
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| 14 | You should have received a copy of the GNU General Public License |
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| 15 | along with this program; if not, write to the Free Software |
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| 16 | Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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| 17 | */ |
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| 18 | |
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| 19 | #ifndef DISJOINT_SET |
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| 20 | #define DISJOINT_SET |
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| 21 | |
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| 22 | // disjoint-set forests using union-by-rank and path compression (sort of). |
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| 23 | |
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| 24 | typedef struct { |
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| 25 | int rank; |
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| 26 | int p; |
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| 27 | int size; |
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| 28 | } uni_elt; |
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| 29 | |
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| 30 | class universe { |
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| 31 | public: |
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| 32 | universe(int elements); |
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| 33 | ~universe(); |
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| 34 | int find(int x); |
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| 35 | void join(int x, int y); |
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| 36 | int size(int x) const { return elts[x].size; } |
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| 37 | int num_sets() const { return num; } |
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| 38 | |
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| 39 | private: |
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| 40 | uni_elt *elts; |
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| 41 | int num; |
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| 42 | }; |
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| 43 | |
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| 44 | universe::universe(int elements) { |
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| 45 | elts = new uni_elt[elements]; |
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| 46 | num = elements; |
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| 47 | for (int i = 0; i < elements; i++) { |
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| 48 | elts[i].rank = 0; |
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| 49 | elts[i].size = 1; |
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| 50 | elts[i].p = i; |
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| 51 | } |
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| 52 | } |
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| 53 | |
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| 54 | universe::~universe() { |
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| 55 | delete [] elts; |
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| 56 | } |
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| 57 | |
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| 58 | int universe::find(int x) { |
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| 59 | int y = x; |
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| 60 | while (y != elts[y].p) |
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| 61 | y = elts[y].p; |
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| 62 | elts[x].p = y; |
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| 63 | return y; |
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| 64 | } |
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| 65 | |
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| 66 | void universe::join(int x, int y) { |
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| 67 | if (elts[x].rank > elts[y].rank) { |
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| 68 | elts[y].p = x; |
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| 69 | elts[x].size += elts[y].size; |
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| 70 | } else { |
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| 71 | elts[x].p = y; |
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| 72 | elts[y].size += elts[x].size; |
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| 73 | if (elts[x].rank == elts[y].rank) |
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| 74 | elts[y].rank++; |
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| 75 | } |
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| 76 | num--; |
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| 77 | } |
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| 78 | |
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| 79 | #endif |
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