godot/core/math/disjoint_set.h
2021-05-05 15:02:01 +02:00

155 lines
5.2 KiB
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/*************************************************************************/
/* disjoint_set.h */
/*************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/*************************************************************************/
/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur. */
/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md). */
/* */
/* 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 */
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/*************************************************************************/
#ifndef DISJOINT_SET_H
#define DISJOINT_SET_H
#include "core/map.h"
#include "core/vector.h"
/**
@author Marios Staikopoulos <marios@staik.net>
*/
/* This DisjointSet class uses Find with path compression and Union by rank */
template <typename T, class C = Comparator<T>, class AL = DefaultAllocator>
class DisjointSet {
struct Element {
T object;
Element *parent = nullptr;
int rank = 0;
};
typedef Map<T, Element *, C, AL> 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, class C, class AL>
DisjointSet<T, C, AL>::~DisjointSet() {
for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
memdelete_allocator<Element, AL>(itr->value());
}
}
template <typename T, class C, class AL>
typename DisjointSet<T, C, AL>::Element *DisjointSet<T, C, AL>::get_parent(Element *element) {
if (element->parent != element) {
element->parent = get_parent(element->parent);
}
return element->parent;
}
template <typename T, class C, class AL>
typename DisjointSet<T, C, AL>::Element *DisjointSet<T, C, AL>::insert_or_get(T object) {
typename MapT::Element *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, class C, class AL>
void DisjointSet<T, 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, class C, class AL>
void DisjointSet<T, C, AL>::get_representatives(Vector<T> &out_representatives) {
for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
Element *element = itr->value();
if (element->parent == element) {
out_representatives.push_back(element->object);
}
}
}
template <typename T, class C, class AL>
void DisjointSet<T, C, AL>::get_members(Vector<T> &out_members, T representative) {
typename MapT::Element *rep_itr = elements.find(representative);
ERR_FAIL_COND(rep_itr == nullptr);
Element *rep_element = rep_itr->value();
ERR_FAIL_COND(rep_element->parent != rep_element);
for (typename MapT::Element *itr = elements.front(); itr != nullptr; itr = itr->next()) {
Element *parent = get_parent(itr->value());
if (parent == rep_element) {
out_members.push_back(itr->key());
}
}
}
#endif