2
* Copyright (C) 2008 Apple Inc. All rights reserved.
4
* Based on Abstract AVL Tree Template v1.5 by Walt Karas
5
* <http://geocities.com/wkaras/gen_cpp/avl_tree.html>.
7
* Redistribution and use in source and binary forms, with or without
8
* modification, are permitted provided that the following conditions
11
* 1. Redistributions of source code must retain the above copyright
12
* notice, this list of conditions and the following disclaimer.
13
* 2. Redistributions in binary form must reproduce the above copyright
14
* notice, this list of conditions and the following disclaimer in the
15
* documentation and/or other materials provided with the distribution.
16
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
17
* its contributors may be used to endorse or promote products derived
18
* from this software without specific prior written permission.
20
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
21
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
22
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
23
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
24
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
25
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
26
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
27
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35
#include <wtf/Assertions.h>
36
#include <wtf/FixedArray.h>
40
// Here is the reference class for BSet.
50
// void operator = (bool b);
53
// // Does not have to initialize bits.
56
// // Must return a valid value for index when 0 <= index < maxDepth
57
// ANY_bitref operator [] (unsigned index);
59
// // Set all bits to 1.
62
// // Set all bits to 0.
66
template<unsigned maxDepth>
67
class AVLTreeDefaultBSet {
69
bool& operator[](unsigned i) { ASSERT(i < maxDepth); return m_data[i]; }
70
void set() { for (unsigned i = 0; i < maxDepth; ++i) m_data[i] = true; }
71
void reset() { for (unsigned i = 0; i < maxDepth; ++i) m_data[i] = false; }
74
FixedArray<bool, maxDepth> m_data;
77
// How to determine maxDepth:
78
// d Minimum number of nodes
124
// E.g., if, in a particular instantiation, the maximum number of nodes in a tree instance is 1,000,000, the maximum depth should be 28.
125
// You pick 28 because MN(28) is 832,039, which is less than or equal to 1,000,000, and MN(29) is 1,346,268, which is strictly greater than 1,000,000.
127
template <class Abstractor, unsigned maxDepth = 32, class BSet = AVLTreeDefaultBSet<maxDepth> >
131
typedef typename Abstractor::key key;
132
typedef typename Abstractor::handle handle;
133
typedef typename Abstractor::size size;
139
LESS_EQUAL = EQUAL | LESS,
140
GREATER_EQUAL = EQUAL | GREATER
144
Abstractor& abstractor() { return abs; }
146
inline handle insert(handle h);
148
inline handle search(key k, SearchType st = EQUAL);
149
inline handle search_least();
150
inline handle search_greatest();
152
inline handle remove(key k);
154
inline handle subst(handle new_node);
156
void purge() { abs.root = null(); }
158
bool is_empty() { return abs.root == null(); }
160
AVLTree() { abs.root = null(); }
165
// Initialize depth to invalid value, to indicate iterator is
166
// invalid. (Depth is zero-base.)
167
Iterator() { depth = ~0U; }
169
void start_iter(AVLTree &tree, key k, SearchType st = EQUAL)
171
// Mask of high bit in an int.
172
const int MASK_HIGH_BIT = (int) ~ ((~ (unsigned) 0) >> 1);
174
// Save the tree that we're going to iterate through in a
179
handle h = tree_->abs.root;
189
// Key can be greater than key of starting node.
191
else if (st & GREATER)
192
// Key can be less than key of starting node.
195
// Key must be same as key of starting node.
202
// Equal node was sought and found as starting node.
207
} else if (target_cmp != 0) {
208
if (!((cmp ^ target_cmp) & MASK_HIGH_BIT)) {
209
// cmp and target_cmp are both negative or both positive.
213
h = cmp < 0 ? get_lt(h) : get_gt(h);
221
void start_iter_least(AVLTree &tree)
225
handle h = tree_->abs.root;
231
while (h != null()) {
239
void start_iter_greatest(AVLTree &tree)
243
handle h = tree_->abs.root;
249
while (h != null()) {
262
return depth == 0 ? tree_->abs.root : path_h[depth - 1];
268
handle h = get_gt(**this);
276
} while (branch[depth]);
278
branch[depth] = true;
284
branch[depth] = false;
294
handle h = get_lt(**this);
302
} while (!branch[depth]);
304
branch[depth] = false;
310
branch[depth] = true;
317
void operator++(int) { ++(*this); }
318
void operator--(int) { --(*this); }
322
// Tree being iterated over.
325
// Records a path into the tree. If branch[n] is true, indicates
326
// take greater branch from the nth node in the path, otherwise
327
// take the less branch. branch[0] gives branch from root, and
331
// Zero-based depth of path into tree.
334
// Handles of nodes in path from root to current node (returned by *).
335
handle path_h[maxDepth - 1];
337
int cmp_k_n(key k, handle h) { return tree_->abs.compare_key_node(k, h); }
338
int cmp_n_n(handle h1, handle h2) { return tree_->abs.compare_node_node(h1, h2); }
339
handle get_lt(handle h) { return tree_->abs.get_less(h); }
340
handle get_gt(handle h) { return tree_->abs.get_greater(h); }
341
handle null() { return tree_->abs.null(); }
344
template<typename fwd_iter>
345
bool build(fwd_iter p, size num_nodes)
347
if (num_nodes == 0) {
352
// Gives path to subtree being built. If branch[N] is false, branch
353
// less from the node at depth N, if true branch greater.
356
// If rem[N] is true, then for the current subtree at depth N, it's
357
// greater subtree has one more node than it's less subtree.
360
// Depth of root node of current subtree.
363
// Number of nodes in current subtree.
364
size num_sub = num_nodes;
366
// The algorithm relies on a stack of nodes whose less subtree has
367
// been built, but whose right subtree has not yet been built. The
368
// stack is implemented as linked list. The nodes are linked
369
// together by having the "greater" handle of a node set to the
370
// next node in the list. "less_parent" is the handle of the first
372
handle less_parent = null();
374
// h is root of current subtree, child is one of its children.
378
while (num_sub > 2) {
379
// Subtract one for root of subtree.
381
rem[depth] = !!(num_sub & 1);
382
branch[depth++] = false;
387
// Build a subtree with two nodes, slanting to greater.
388
// I arbitrarily chose to always have the extra node in the
389
// greater subtree when there is an odd number of nodes to
390
// split between the two subtrees.
396
set_lt(child, null());
397
set_gt(child, null());
402
} else { // num_sub == 1
403
// Build a subtree with one node.
415
// We've completed a less subtree.
418
// We've completed a greater subtree, so attach it to
419
// its parent (that is less than it). We pop the parent
420
// off the stack of less parents.
423
less_parent = get_gt(h);
425
// num_sub = 2 * (num_sub - rem[depth]) + rem[depth] + 1
427
num_sub += 1 - rem[depth];
428
if (num_sub & (num_sub - 1))
429
// num_sub is not a power of 2
432
// num_sub is a power of 2
436
if (num_sub == num_nodes)
437
// We've completed the full tree.
440
// The subtree we've completed is the less subtree of the
441
// next node in the sequence.
448
// Put h into stack of less parents.
449
set_gt(h, less_parent);
452
// Proceed to creating greater than subtree of h.
453
branch[depth] = true;
454
num_sub += rem[depth++];
465
friend class Iterator;
467
// Create a class whose sole purpose is to take advantage of
468
// the "empty member" optimization.
469
struct abs_plus_root : public Abstractor {
470
// The handle of the root element in the AVL tree.
477
handle get_lt(handle h) { return abs.get_less(h); }
478
void set_lt(handle h, handle lh) { abs.set_less(h, lh); }
480
handle get_gt(handle h) { return abs.get_greater(h); }
481
void set_gt(handle h, handle gh) { abs.set_greater(h, gh); }
483
int get_bf(handle h) { return abs.get_balance_factor(h); }
484
void set_bf(handle h, int bf) { abs.set_balance_factor(h, bf); }
486
int cmp_k_n(key k, handle h) { return abs.compare_key_node(k, h); }
487
int cmp_n_n(handle h1, handle h2) { return abs.compare_node_node(h1, h2); }
489
handle null() { return abs.null(); }
493
// Balances subtree, returns handle of root node of subtree
495
handle balance(handle bal_h)
499
// Either the "greater than" or the "less than" subtree of
500
// this node has to be 2 levels deeper (or else it wouldn't
503
if (get_bf(bal_h) > 0) {
504
// "Greater than" subtree is deeper.
506
deep_h = get_gt(bal_h);
508
if (get_bf(deep_h) < 0) {
509
handle old_h = bal_h;
510
bal_h = get_lt(deep_h);
512
set_gt(old_h, get_lt(bal_h));
513
set_lt(deep_h, get_gt(bal_h));
514
set_lt(bal_h, old_h);
515
set_gt(bal_h, deep_h);
517
int bf = get_bf(bal_h);
532
set_gt(bal_h, get_lt(deep_h));
533
set_lt(deep_h, bal_h);
534
if (get_bf(deep_h) == 0) {
544
// "Less than" subtree is deeper.
546
deep_h = get_lt(bal_h);
548
if (get_bf(deep_h) > 0) {
549
handle old_h = bal_h;
550
bal_h = get_gt(deep_h);
551
set_lt(old_h, get_gt(bal_h));
552
set_gt(deep_h, get_lt(bal_h));
553
set_gt(bal_h, old_h);
554
set_lt(bal_h, deep_h);
556
int bf = get_bf(bal_h);
571
set_lt(bal_h, get_gt(deep_h));
572
set_gt(deep_h, bal_h);
573
if (get_bf(deep_h) == 0) {
589
template <class Abstractor, unsigned maxDepth, class BSet>
590
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
591
AVLTree<Abstractor, maxDepth, BSet>::insert(handle h)
597
if (abs.root == null())
600
// Last unbalanced node encountered in search for insertion point.
601
handle unbal = null();
602
// Parent of last unbalanced node.
603
handle parent_unbal = null();
604
// Balance factor of last unbalanced node.
607
// Zero-based depth in tree.
608
unsigned depth = 0, unbal_depth = 0;
610
// Records a path into the tree. If branch[n] is true, indicates
611
// take greater branch from the nth node in the path, otherwise
612
// take the less branch. branch[0] gives branch from root, and
616
handle hh = abs.root;
617
handle parent = null();
621
if (get_bf(hh) != 0) {
623
parent_unbal = parent;
626
cmp = cmp_n_n(h, hh);
631
hh = cmp < 0 ? get_lt(hh) : get_gt(hh);
632
branch[depth++] = cmp > 0;
633
} while (hh != null());
635
// Add node to insert as leaf of tree.
646
cmp = branch[depth++] ? 1 : -1;
647
unbal_bf = get_bf(unbal);
652
hh = cmp < 0 ? get_lt(unbal) : get_gt(unbal);
653
if ((unbal_bf != -2) && (unbal_bf != 2)) {
654
// No rebalancing of tree is necessary.
655
set_bf(unbal, unbal_bf);
662
cmp = branch[depth++] ? 1 : -1;
672
if (unbal != null()) {
673
unbal = balance(unbal);
674
if (parent_unbal == null())
677
depth = unbal_depth - 1;
678
cmp = branch[depth] ? 1 : -1;
680
set_lt(parent_unbal, unbal);
682
set_gt(parent_unbal, unbal);
690
template <class Abstractor, unsigned maxDepth, class BSet>
691
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
692
AVLTree<Abstractor, maxDepth, BSet>::search(key k, typename AVLTree<Abstractor, maxDepth, BSet>::SearchType st)
694
const int MASK_HIGH_BIT = (int) ~ ((~ (unsigned) 0) >> 1);
697
handle match_h = null();
702
else if (st & GREATER)
707
while (h != null()) {
715
} else if (target_cmp != 0)
716
if (!((cmp ^ target_cmp) & MASK_HIGH_BIT))
717
// cmp and target_cmp are both positive or both negative.
719
h = cmp < 0 ? get_lt(h) : get_gt(h);
725
template <class Abstractor, unsigned maxDepth, class BSet>
726
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
727
AVLTree<Abstractor, maxDepth, BSet>::search_least()
729
handle h = abs.root, parent = null();
731
while (h != null()) {
739
template <class Abstractor, unsigned maxDepth, class BSet>
740
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
741
AVLTree<Abstractor, maxDepth, BSet>::search_greatest()
743
handle h = abs.root, parent = null();
745
while (h != null()) {
753
template <class Abstractor, unsigned maxDepth, class BSet>
754
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
755
AVLTree<Abstractor, maxDepth, BSet>::remove(key k)
757
// Zero-based depth in tree.
758
unsigned depth = 0, rm_depth;
760
// Records a path into the tree. If branch[n] is true, indicates
761
// take greater branch from the nth node in the path, otherwise
762
// take the less branch. branch[0] gives branch from root, and
767
handle parent = null(), child;
768
int cmp, cmp_shortened_sub_with_path = 0;
772
// No node in tree with given key.
776
// Found node to remove.
779
h = cmp < 0 ? get_lt(h) : get_gt(h);
780
branch[depth++] = cmp > 0;
781
cmp_shortened_sub_with_path = cmp;
784
handle parent_rm = parent;
787
// If the node to remove is not a leaf node, we need to get a
788
// leaf node, or a node with a single leaf as its child, to put
789
// in the place of the node to remove. We will get the greatest
790
// node in the less subtree (of the node to remove), or the least
791
// node in the greater subtree. We take the leaf node from the
792
// deeper subtree, if there is one.
796
branch[depth] = false;
800
branch[depth] = true;
805
if (child != null()) {
812
branch[depth] = false;
815
branch[depth] = true;
818
} while (child != null());
821
// Only went through do loop once. Deleted node will be replaced
822
// in the tree structure by one of its immediate children.
823
cmp_shortened_sub_with_path = -cmp;
825
cmp_shortened_sub_with_path = cmp;
827
// Get the handle of the opposite child, which may not be null.
828
child = cmp > 0 ? get_lt(h) : get_gt(h);
831
if (parent == null())
832
// There were only 1 or 2 nodes in this tree.
834
else if (cmp_shortened_sub_with_path < 0)
835
set_lt(parent, child);
837
set_gt(parent, child);
839
// "path" is the parent of the subtree being eliminated or reduced
840
// from a depth of 2 to 1. If "path" is the node to be removed, we
841
// set path to the node we're about to poke into the position of the
842
// node to be removed.
843
handle path = parent == rm ? h : parent;
846
// Poke in the replacement for the node to be removed.
847
set_lt(h, get_lt(rm));
848
set_gt(h, get_gt(rm));
849
set_bf(h, get_bf(rm));
850
if (parent_rm == null())
853
depth = rm_depth - 1;
855
set_gt(parent_rm, h);
857
set_lt(parent_rm, h);
861
if (path != null()) {
862
// Create a temporary linked list from the parent of the path node
868
if (branch[depth++]) {
879
// Climb from the path node to the root node using the linked
880
// list, restoring the tree structure and rebalancing as necessary.
881
bool reduced_depth = true;
883
cmp = cmp_shortened_sub_with_path;
891
if ((bf == -2) || (bf == 2)) {
896
reduced_depth = (bf == 0);
898
if (parent == null())
902
cmp = branch[--depth] ? 1 : -1;
917
template <class Abstractor, unsigned maxDepth, class BSet>
918
inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
919
AVLTree<Abstractor, maxDepth, BSet>::subst(handle new_node)
922
handle parent = null();
925
/* Search for node already in tree with same key. */
928
/* No node in tree with same key as new node. */
930
cmp = cmp_n_n(new_node, h);
932
/* Found the node to substitute new one for. */
936
h = cmp < 0 ? get_lt(h) : get_gt(h);
939
/* Copy tree housekeeping fields from node in tree to new node. */
940
set_lt(new_node, get_lt(h));
941
set_gt(new_node, get_gt(h));
942
set_bf(new_node, get_bf(h));
944
if (parent == null())
945
/* New node is also new root. */
948
/* Make parent point to new node. */
950
set_lt(parent, new_node);
952
set_gt(parent, new_node);