initial commit, 4.5 stable

core/math/disjoint_set.h

@@ -0,0 +1,147 @@
+/**************************************************************************/
+/*  disjoint_set.h                                                        */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#pragma once
+
+#include "core/templates/hash_map.h"
+#include "core/templates/vector.h"
+
+/* This DisjointSet class uses Find with path compression and Union by rank */
+template <typename T, typename H = HashMapHasherDefault, typename C = HashMapComparatorDefault<T>, typename AL = DefaultAllocator>
+class DisjointSet {
+	struct Element {
+		T object;
+		Element *parent = nullptr;
+		int rank = 0;
+	};
+
+	typedef HashMap<T, Element *, H, C> MapT;
+
+	MapT elements;
+
+	Element *get_parent(Element *element);
+
+	_FORCE_INLINE_ Element *insert_or_get(T object);
+
+public:
+	~DisjointSet();
+
+	_FORCE_INLINE_ void insert(T object) { (void)insert_or_get(object); }
+
+	void create_union(T a, T b);
+
+	void get_representatives(Vector<T> &out_roots);
+
+	void get_members(Vector<T> &out_members, T representative);
+};
+
+/* FUNCTIONS */
+
+template <typename T, typename H, typename C, typename AL>
+DisjointSet<T, H, C, AL>::~DisjointSet() {
+	for (KeyValue<T, Element *> &E : elements) {
+		memdelete_allocator<Element, AL>(E.value);
+	}
+}
+
+template <typename T, typename H, typename C, typename AL>
+typename DisjointSet<T, H, C, AL>::Element *DisjointSet<T, H, C, AL>::get_parent(Element *element) {
+	if (element->parent != element) {
+		element->parent = get_parent(element->parent);
+	}
+
+	return element->parent;
+}
+
+template <typename T, typename H, typename C, typename AL>
+typename DisjointSet<T, H, C, AL>::Element *DisjointSet<T, H, C, AL>::insert_or_get(T object) {
+	typename MapT::Iterator itr = elements.find(object);
+	if (itr != nullptr) {
+		return itr->value;
+	}
+
+	Element *new_element = memnew_allocator(Element, AL);
+	new_element->object = object;
+	new_element->parent = new_element;
+	elements.insert(object, new_element);
+
+	return new_element;
+}
+
+template <typename T, typename H, typename C, typename AL>
+void DisjointSet<T, H, C, AL>::create_union(T a, T b) {
+	Element *x = insert_or_get(a);
+	Element *y = insert_or_get(b);
+
+	Element *x_root = get_parent(x);
+	Element *y_root = get_parent(y);
+
+	// Already in the same set
+	if (x_root == y_root) {
+		return;
+	}
+
+	// Not in the same set, merge
+	if (x_root->rank < y_root->rank) {
+		SWAP(x_root, y_root);
+	}
+
+	// Merge y_root into x_root
+	y_root->parent = x_root;
+	if (x_root->rank == y_root->rank) {
+		++x_root->rank;
+	}
+}
+
+template <typename T, typename H, typename C, typename AL>
+void DisjointSet<T, H, C, AL>::get_representatives(Vector<T> &out_representatives) {
+	for (KeyValue<T, Element *> &E : elements) {
+		Element *element = E.value;
+		if (element->parent == element) {
+			out_representatives.push_back(element->object);
+		}
+	}
+}
+
+template <typename T, typename H, typename C, typename AL>
+void DisjointSet<T, H, C, AL>::get_members(Vector<T> &out_members, T representative) {
+	typename MapT::Iterator rep_itr = elements.find(representative);
+	ERR_FAIL_NULL(rep_itr);
+
+	Element *rep_element = rep_itr->value;
+	ERR_FAIL_COND(rep_element->parent != rep_element);
+
+	for (KeyValue<T, Element *> &E : elements) {
+		Element *parent = get_parent(E.value);
+		if (parent == rep_element) {
+			out_members.push_back(E.key);
+		}
+	}
+}