Campbell Barton
c434782e3a
Use a shorter/simpler license convention, stops the header taking so much space. Follow the SPDX license specification: https://spdx.org/licenses - C/C++/objc/objc++ - Python - Shell Scripts - CMake, GNUmakefile While most of the source tree has been included - `./extern/` was left out. - `./intern/cycles` & `./intern/atomic` are also excluded because they use different header conventions. doc/license/SPDX-license-identifiers.txt has been added to list SPDX all used identifiers. See P2788 for the script that automated these edits. Reviewed By: brecht, mont29, sergey Ref D14069
90 lines
1.8 KiB
C++
90 lines
1.8 KiB
C++
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#pragma once
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/** \file
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* \ingroup bli
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*
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* This implements the disjoint set data structure with path compression and union by rank.
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*/
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#include "BLI_array.hh"
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namespace blender {
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class DisjointSet {
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private:
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Array<int64_t> parents_;
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Array<int64_t> ranks_;
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public:
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/**
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* Create a new disjoint set with the given size. Initially, every element is in a separate set.
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*/
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DisjointSet(int64_t size) : parents_(size), ranks_(size, 0)
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{
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BLI_assert(size >= 0);
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for (int64_t i = 0; i < size; i++) {
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parents_[i] = i;
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}
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}
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/**
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* Join the sets containing elements x and y. Nothing happens when they have been in the same set
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* before.
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*/
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void join(int64_t x, int64_t y)
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{
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int64_t root1 = this->find_root(x);
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int64_t root2 = this->find_root(y);
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/* x and y are in the same set already. */
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if (root1 == root2) {
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return;
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}
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/* Implement union by rank heuristic. */
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if (ranks_[root1] < ranks_[root2]) {
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std::swap(root1, root2);
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}
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parents_[root2] = root1;
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if (ranks_[root1] == ranks_[root2]) {
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ranks_[root1]++;
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}
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}
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/**
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* Return true when x and y are in the same set.
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*/
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bool in_same_set(int64_t x, int64_t y)
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{
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int64_t root1 = this->find_root(x);
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int64_t root2 = this->find_root(y);
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return root1 == root2;
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}
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/**
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* Find the element that represents the set containing x currently.
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*/
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int64_t find_root(int64_t x)
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{
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/* Find root by following parents. */
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int64_t root = x;
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while (parents_[root] != root) {
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root = parents_[root];
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}
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/* Compress path. */
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while (parents_[x] != root) {
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int64_t parent = parents_[x];
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parents_[x] = root;
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x = parent;
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}
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return root;
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}
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};
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} // namespace blender
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