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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* $URL$
* $Id$
*
*/
#ifndef SCI_ENGINE_AATREE_H
#define SCI_ENGINE_AATREE_H
#include "common/func.h"
namespace Sci {
// Andersson tree implementation.
template<typename Key>
struct AATreeNode {
AATreeNode() : _left(this), _right(this), _level(0) { }
AATreeNode(const Key &key, AATreeNode *left, AATreeNode *right, int level) : _key(key), _left(left), _right(right), _level(level) { }
Key _key;
AATreeNode *_left, *_right;
int _level;
};
template<typename Key, class LessFunc = Common::Less<Key> >
class AATree {
public:
AATree() {
_bottom = new AATreeNode<Key>;
_root = _bottom;
}
AATree(const AATree<Key, LessFunc> &tree) {
_bottom = new AATreeNode<Key>;
_root = copyTree(tree._root, tree._bottom);
}
const AATree<Key, LessFunc> &operator=(const AATree<Key, LessFunc> &tree) {
if (this != &tree) {
freeNode(_root);
_root = copyTree(tree._root, tree._bottom);
}
return *this;
}
~AATree() {
freeNode(_root);
delete _bottom;
}
void insert(const Key &key) {
insertNode(key, _root);
}
bool remove(const Key &key) {
return removeNode(key, _root);
}
// Returns a pointer to the smallest Key or NULL if the tree is empty.
const Key *findSmallest() const {
AATreeNode<Key> *node = _root;
if (node == _bottom)
return NULL;
while (node->_left != _bottom)
node = node->_left;
return &node->_key;
}
private:
AATreeNode<Key> *_root;
AATreeNode<Key> *_bottom;
LessFunc _less;
private:
void freeNode(AATreeNode<Key> *node) {
if (node == _bottom)
return;
freeNode(node->_left);
freeNode(node->_right);
delete node;
}
void skew(AATreeNode<Key> *&node) {
if (node->_left->_level == node->_level) {
// Rotate right
AATreeNode<Key> *temp = node;
node = node->_left;
temp->_left = node->_right;
node->_right = temp;
}
}
void split(AATreeNode<Key> *&node) {
if (node->_right->_right->_level == node->_level) {
// Rotate left
AATreeNode<Key> *temp = node;
node = node->_right;
temp->_right = node->_left;
node->_left = temp;
node->_level++;
}
}
bool removeNode(const Key &key, AATreeNode<Key> *&node) {
bool ok = false;
static AATreeNode<Key> *last, *deleted = _bottom;
if (node != _bottom) {
// Search down the tree and set pointers last and deleted
last = node;
if (_less(key, node->_key))
ok = removeNode(key, node->_left);
else {
deleted = node;
ok = removeNode(key, node->_right);
}
if ((node == last) && (deleted != _bottom) && !_less(key, deleted->_key) && !_less(deleted->_key, key)) {
// At the bottom of the tree we remove the element (if it is present)
deleted->_key = node->_key;
deleted = _bottom;
node = node->_right;
delete last;
return true;
}
if ((node->_left->_level < node->_level - 1) || (node->_right->_level < node->_level - 1)) {
// On the way back, we rebalance
node->_level--;
if (node->_right->_level > node->_level)
node->_right->_level = node->_level;
skew(node);
skew(node->_right);
skew(node->_right->_right);
split(node);
split(node->_right);
}
}
return ok;
}
void insertNode(const Key &key, AATreeNode<Key> *&node) {
if (node == _bottom) {
node = new AATreeNode<Key>(key, _bottom, _bottom, 1);
assert(node);
return;
}
if (_less(key, node->_key))
insertNode(key, node->_left);
else if (_less(node->_key, key))
insertNode(key, node->_right);
skew(node);
split(node);
}
AATreeNode<Key> *copyTree(AATreeNode<Key> *node, const AATreeNode<Key> *bottom) {
if (node == bottom)
return _bottom;
return new AATreeNode<Key>(node->_key, copyTree(node->_left, bottom), copyTree(node->_right, bottom), node->_level);
}
};
} // End of namespace Sci
#endif // SCI_ENIGNE_AATREE_H
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