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Happy new year to the wonderful Godot community!
2020 has been a tough year for most of us personally, but a good year for
Godot development nonetheless with a huge amount of work done towards Godot
4.0 and great improvements backported to the long-lived 3.2 branch.
We've had close to 400 contributors to engine code this year, authoring near
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Here's to a great year 2021 for all Godot users 🎆
154 lines
5.2 KiB
C++
154 lines
5.2 KiB
C++
/*************************************************************************/
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/* disjoint_set.h */
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/*************************************************************************/
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/* This file is part of: */
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/* GODOT ENGINE */
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/* https://godotengine.org */
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/*************************************************************************/
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur. */
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/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md). */
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/* */
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/* Permission is hereby granted, free of charge, to any person obtaining */
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/* a copy of this software and associated documentation files (the */
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/* "Software"), to deal in the Software without restriction, including */
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/* without limitation the rights to use, copy, modify, merge, publish, */
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/* distribute, sublicense, and/or sell copies of the Software, and to */
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/* permit persons to whom the Software is furnished to do so, subject to */
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/* the following conditions: */
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/* */
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/* The above copyright notice and this permission notice shall be */
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/* included in all copies or substantial portions of the Software. */
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/* */
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/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
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/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
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/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
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/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
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/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
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/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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/*************************************************************************/
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#ifndef DISJOINT_SET_H
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#define DISJOINT_SET_H
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#include "core/templates/map.h"
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#include "core/templates/vector.h"
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/**
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@author Marios Staikopoulos <marios@staik.net>
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*/
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/* This DisjointSet class uses Find with path compression and Union by rank */
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template <typename T, class C = Comparator<T>, class AL = DefaultAllocator>
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class DisjointSet {
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struct Element {
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T object;
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Element *parent = nullptr;
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int rank = 0;
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};
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typedef Map<T, Element *, C, AL> MapT;
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MapT elements;
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Element *get_parent(Element *element);
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_FORCE_INLINE_ Element *insert_or_get(T object);
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public:
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~DisjointSet();
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_FORCE_INLINE_ void insert(T object) { (void)insert_or_get(object); }
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void create_union(T a, T b);
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void get_representatives(Vector<T> &out_roots);
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void get_members(Vector<T> &out_members, T representative);
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};
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/* FUNCTIONS */
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template <typename T, class C, class AL>
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DisjointSet<T, C, AL>::~DisjointSet() {
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for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
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memdelete_allocator<Element, AL>(itr->value());
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}
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}
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template <typename T, class C, class AL>
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typename DisjointSet<T, C, AL>::Element *DisjointSet<T, C, AL>::get_parent(Element *element) {
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if (element->parent != element) {
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element->parent = get_parent(element->parent);
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}
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return element->parent;
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}
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template <typename T, class C, class AL>
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typename DisjointSet<T, C, AL>::Element *DisjointSet<T, C, AL>::insert_or_get(T object) {
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typename MapT::Element *itr = elements.find(object);
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if (itr != nullptr) {
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return itr->value();
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}
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Element *new_element = memnew_allocator(Element, AL);
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new_element->object = object;
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new_element->parent = new_element;
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elements.insert(object, new_element);
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return new_element;
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}
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template <typename T, class C, class AL>
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void DisjointSet<T, C, AL>::create_union(T a, T b) {
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Element *x = insert_or_get(a);
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Element *y = insert_or_get(b);
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Element *x_root = get_parent(x);
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Element *y_root = get_parent(y);
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// Already in the same set
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if (x_root == y_root) {
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return;
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}
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// Not in the same set, merge
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if (x_root->rank < y_root->rank) {
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SWAP(x_root, y_root);
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}
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// Merge y_root into x_root
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y_root->parent = x_root;
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if (x_root->rank == y_root->rank) {
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++x_root->rank;
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}
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}
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template <typename T, class C, class AL>
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void DisjointSet<T, C, AL>::get_representatives(Vector<T> &out_representatives) {
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for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
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Element *element = itr->value();
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if (element->parent == element) {
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out_representatives.push_back(element->object);
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}
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}
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}
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template <typename T, class C, class AL>
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void DisjointSet<T, C, AL>::get_members(Vector<T> &out_members, T representative) {
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typename MapT::Element *rep_itr = elements.find(representative);
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ERR_FAIL_COND(rep_itr == nullptr);
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Element *rep_element = rep_itr->value();
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ERR_FAIL_COND(rep_element->parent != rep_element);
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for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
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Element *parent = get_parent(itr->value());
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if (parent == rep_element) {
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out_members.push_back(itr->key());
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}
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}
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}
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#endif // DISJOINT_SET_H
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