quadtree.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  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
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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*/
 
 
# ifndef QUADTREE_H
# define QUADTREE_H
 
# include <quadnode.H>
 
class QuadTree 
{
public:
  using Node = QuadNode;
 
private:
  Node * root;  
 
  size_t max_num_points_per_node;
 
  [[nodiscard]] static Node * make_root(
      const Geom_Number & min_x, const Geom_Number & max_x,
      const Geom_Number & min_y, const Geom_Number & max_y,
      const size_t capacity)
  {
    ah_domain_error_if(capacity == 0)
      << "QuadTree leaf capacity must be greater than zero";
    return new Node(min_x, max_x, min_y, max_y);
  }
 
  [[nodiscard]] static bool contains_only(Node * node, const Point & p)
  {
    assert(node != nullptr and node->is_leaf());
    for (const Point & point : node->get_points_set())
      if (point != p)
        return false;
    return true;
  }
 
  [[nodiscard]] static bool has_four_leaf_children(Node * node) noexcept
  {
    return node != nullptr and not node->is_leaf() and
           NW_CHILD(node) != nullptr and NW_CHILD(node)->is_leaf() and
           NE_CHILD(node) != nullptr and NE_CHILD(node)->is_leaf() and
           SW_CHILD(node) != nullptr and SW_CHILD(node)->is_leaf() and
           SE_CHILD(node) != nullptr and SE_CHILD(node)->is_leaf();
  }
 
  [[nodiscard]] static size_t leaf_children_size(Node * node) noexcept
  {
    assert(has_four_leaf_children(node));
    return NW_CHILD(node)->get_points_set().size() +
           NE_CHILD(node)->get_points_set().size() +
           SW_CHILD(node)->get_points_set().size() +
           SE_CHILD(node)->get_points_set().size();
  }
 
  void split(Node * node)
  {
    assert(node->is_leaf()); // Only applies to leaf nodes
 
    size_t next_level = LEVEL(node) + 1;
 
    NW_CHILD(node) =
      new QuadNode(node->get_min_x(), node->get_mid_x(),
                    node->get_min_y(), node->get_mid_y(), node);
    LEVEL(NW_CHILD(node)) = next_level; 
 
    NE_CHILD(node) =
      new QuadNode(node->get_mid_x(), node->get_max_x(),
                    node->get_min_y(), node->get_mid_y(), node);
    LEVEL(NE_CHILD(node)) = next_level;
 
    SW_CHILD(node) =
      new QuadNode(node->get_min_x(), node->get_mid_x(),
                    node->get_mid_y(), node->get_max_y(), node);
    LEVEL(SW_CHILD(node)) = next_level;
 
    SE_CHILD(node) =
      new QuadNode(node->get_mid_x(), node->get_max_x(),
                    node->get_mid_y(), node->get_max_y(), node);
    LEVEL(SE_CHILD(node)) = next_level;
 
    COLOR(node) = Node::Color::Gray;
 
    DynList<Point> & points = node->get_points_set();
    
    while (not points.is_empty())
      {
        Point point = points.remove_first();
 
        QuadNode * child = node->get_child_to(point);
 
        child->add_point(point);
      }
  }
 
  void join(Node * node)
  {
    assert(not node->is_leaf()); // node is not a leaf
    // All four children of node must be leaves
    assert(NW_CHILD(node)->is_leaf());
    assert(NE_CHILD(node)->is_leaf());
    assert(SW_CHILD(node)->is_leaf());
    assert(SE_CHILD(node)->is_leaf());
 
    DynList<Point> & points = node->get_points_set();
 
    DynList<Point> & nw_points = NW_CHILD(node)->get_points_set();
 
    while(not nw_points.is_empty())
      points.append(nw_points.remove_first());
 
    auto & ne_points = NE_CHILD(node)->get_points_set();
 
    while(not ne_points.is_empty())
      points.append(ne_points.remove_first());
 
    auto & sw_points = SW_CHILD(node)->get_points_set();
 
    while(not sw_points.is_empty())
      points.append(sw_points.remove_first());
 
    auto & se_points = SE_CHILD(node)->get_points_set();
 
    while(not se_points.is_empty())
      points.append(se_points.remove_first());
 
    delete NW_CHILD(node);
    NW_CHILD(node) = nullptr;
  
    delete NE_CHILD(node);
    NE_CHILD(node) = nullptr;
 
    delete SW_CHILD(node);
    SW_CHILD(node) = nullptr;
 
    delete SE_CHILD(node);
    SE_CHILD(node) = nullptr;
 
    COLOR(node) = points.is_empty() ? Node::Color::White : Node::Color::Black;
  }
 
  Point * insert(Node *& r, const Point & p)
  {
    assert(r->contains(p));
 
    if (r->is_leaf())
      {
        if (r->get_points_set().size() < max_num_points_per_node or
            contains_only(r, p))
          return &r->add_point(p);
 
        split(r);
      }
  
    Node * node = r->get_child_to(p);
 
    return insert(node, p);
  }
 
  void empty(Node *& r) noexcept
  {
    if (r == nullptr)
      return;
 
    empty(NW_CHILD(r));
    empty(NE_CHILD(r));
    empty(SW_CHILD(r));
    empty(SE_CHILD(r));
 
    delete r;
    r = nullptr;
  }
 
  template <class Op>
  void operate_on_nodes(Node * r, Op & op)
  {
    if (r == nullptr)
      return;
 
    op(r);
 
    operate_on_nodes<Op> (NW_CHILD(r), op);
    operate_on_nodes<Op> (NE_CHILD(r), op);
    operate_on_nodes<Op> (SW_CHILD(r), op);
    operate_on_nodes<Op> (SE_CHILD(r), op);
  }
 
  void copy_tree(QuadNode * src, QuadNode *& tgt,
                 QuadNode * tgt_parent = nullptr)
  {
    if (src == nullptr)
      return;
 
    if (src->get_min_x() < src->get_max_x() and
        src->get_min_y() < src->get_max_y())
      tgt = new QuadNode(src->get_min_x(), src->get_max_x(),
                         src->get_min_y(), src->get_max_y(), tgt_parent);
    else
      {
        // Preserve the explicitly uninitialized state of a default tree.
        tgt = new QuadNode;
        PARENT(tgt) = tgt_parent;
      }
 
    tgt->get_points_set() = src->get_points_set();
 
    COLOR(tgt) = COLOR(src);
    LEVEL(tgt) = LEVEL(src);
 
    copy_tree(NW_CHILD(src), NW_CHILD(tgt), tgt);
    copy_tree(NE_CHILD(src), NE_CHILD(tgt), tgt);
    copy_tree(SW_CHILD(src), SW_CHILD(tgt), tgt);
    copy_tree(SE_CHILD(src), SE_CHILD(tgt), tgt);
  }
 
public:
 
  QuadTree()
    : root(new Node), max_num_points_per_node(1)
  {
    // Empty
  }
  
  QuadTree(const Geom_Number & min_x, const Geom_Number & max_x,
     const Geom_Number & min_y, const Geom_Number & max_y,
     const size_t & _max_num_points_per_node = 1)
    : root(make_root(min_x, max_x, min_y, max_y,
                     _max_num_points_per_node)),
      max_num_points_per_node(_max_num_points_per_node)
  {
    // Empty
  }
  
  QuadTree(const QuadTree & tree)
    : root(nullptr), max_num_points_per_node(tree.max_num_points_per_node)
  {
    copy_tree(tree.root, root);
  }
 
  QuadTree(QuadTree && tree) noexcept
    : root(tree.root), max_num_points_per_node(tree.max_num_points_per_node)
  {
    tree.root = nullptr;
  }
 
  QuadTree & operator = (const QuadTree & tree)
  {
    if (this == &tree)
      return *this;
 
    empty(root);
    max_num_points_per_node = tree.max_num_points_per_node;
    copy_tree(tree.root, root);
 
    return *this;
  }
 
  QuadTree & operator = (QuadTree && tree) noexcept
  {
    if (this != &tree)
      {
        empty(root);
        root = tree.root;
        max_num_points_per_node = tree.max_num_points_per_node;
        tree.root = nullptr;
      }
    return *this;
  }
 
  ~QuadTree()
  {
    empty(root);
  }
 
  [[nodiscard]] Node * get_root() noexcept
  {
    return root;
  }
 
  [[nodiscard]] const Node * get_root() const noexcept
  {
    return root;
  }
 
  void set_max_num_points_per_node(const size_t & _max_num_points_per_node)
  {
    ah_domain_error_if(_max_num_points_per_node == 0)
      << "QuadTree leaf capacity must be greater than zero";
    max_num_points_per_node = _max_num_points_per_node;
  }
 
  [[nodiscard]] size_t get_max_num_points_per_node() const noexcept
  {
    return max_num_points_per_node;
  }
 
  [[nodiscard]] bool contains(const Point & p) const noexcept
  {
    return root != nullptr and root->contains(p);
  }
 
  Point * insert(const Point & p)
  {
    if (root == nullptr or not root->contains(p))
      return nullptr;
 
    return insert(root, p);
  }
 
  Point * insert(const Geom_Number & x, const Geom_Number & y)
  {
    return insert(Point(x, y));
  }
  
  [[nodiscard]] Point * search(const Point & p) noexcept
  {
    if (root == nullptr or not root->contains(p))
      return nullptr;
 
    Node * aux = root;
 
    while (not aux->is_leaf())
      aux = aux->get_child_to(p);
 
    return aux->search_point(p);
  }
 
  [[nodiscard]] Node * search_container_node(const Point & p) noexcept
  {
    if (root == nullptr or not root->contains(p))
      return nullptr;
 
    Node * aux = root;
 
    while (not aux->is_leaf())
      aux = aux->get_child_to(p);
 
    if (aux->search_point(p) == nullptr)
      return nullptr;
 
    return aux;
  }
 
  void remove(const Point & p)
  {
    if (root == nullptr or not root->contains(p))
      return;
 
    Node * aux = root;
 
    while (not aux->is_leaf())
      aux = aux->get_child_to(p);
 
    if (not aux->remove_point(p))
      return;
 
    Node * parent = PARENT(aux);
    while (parent != nullptr and has_four_leaf_children(parent) and
           leaf_children_size(parent) <= max_num_points_per_node)
      {
        Node * grandparent = PARENT(parent);
        join(parent);
        parent = grandparent;
      }
  }
 
  void empty()
  {
    if (root == nullptr)
      return;
 
    empty(NW_CHILD(root));
    empty(NE_CHILD(root));
    empty(SW_CHILD(root));
    empty(SE_CHILD(root));
    root->empty();
  }
 
  void clear() { empty(); }
 
  template <class Op>
  void for_each(Op & op)
  {
    operate_on_nodes <Op> (root, op);
  }
 
  template <class Op>
  void for_each(Op && op = Op())
  { 
    operate_on_nodes <Op> (root, op);
  }
};
 
# endif // QUADTREE_H