1
/* ========================================================================== **
4
* Copyright (C) 1993-1998 by Christopher R. Hertel
6
* Email: crh@ubiqx.mn.org
7
* -------------------------------------------------------------------------- **
9
* This module implements "splay" trees. Splay trees are binary trees
10
* that are rearranged (splayed) whenever a node is accessed. The
11
* splaying process *tends* to make the tree bushier (improves balance),
12
* and the nodes that are accessed most frequently *tend* to be closer to
15
* References: "Self-Adjusting Binary Search Trees", by Daniel Sleator and
16
* Robert Tarjan. Journal of the Association for Computing
17
* Machinery Vol 32, No. 3, July 1985 pp. 652-686
19
* See also: http://www.cs.cmu.edu/~sleator/
21
* -------------------------------------------------------------------------- **
23
* This library is free software; you can redistribute it and/or
24
* modify it under the terms of the GNU Library General Public
25
* License as published by the Free Software Foundation; either
26
* version 2 of the License, or (at your option) any later version.
28
* This library is distributed in the hope that it will be useful,
29
* but WITHOUT ANY WARRANTY; without even the implied warranty of
30
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
31
* Library General Public License for more details.
33
* You should have received a copy of the GNU Library General Public
34
* License along with this library; if not, write to the Free
35
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
37
* -------------------------------------------------------------------------- **
39
* Log: ubi_SplayTree.c,v
40
* Revision 4.5 2000/01/08 23:26:49 crh
41
* Added ubi_trSplay() macro, which does a type cast for us.
43
* Revision 4.4 1998/06/04 21:29:27 crh
44
* Upper-cased defined constants (eg UBI_BINTREE_H) in some header files.
45
* This is more "standard", and is what people expect. Weird, eh?
47
* Revision 4.3 1998/06/03 17:45:05 crh
48
* Further fiddling with sys_include.h. It's now in ubi_BinTree.h which is
49
* included by all of the binary tree files.
51
* Also fixed some warnings produced by lint on Irix 6.2, which doesn't seem
52
* to like syntax like this:
56
* The fix was to change lines like the above to:
60
* Which means the same thing.
62
* Reminder: Some of the ubi_tr* macros in ubi_BinTree.h are redefined in
63
* ubi_AVLtree.h and ubi_SplayTree.h. This allows easy swapping
64
* of tree types by simply changing a header. Unfortunately, the
65
* macro redefinitions in ubi_AVLtree.h and ubi_SplayTree.h will
66
* conflict if used together. You must either choose a single tree
67
* type, or use the underlying function calls directly. Compare
68
* the two header files for more information.
70
* Revision 4.2 1998/06/02 01:29:14 crh
71
* Changed ubi_null.h to sys_include.h to make it more generic.
73
* Revision 4.1 1998/05/20 04:37:54 crh
74
* The C file now includes ubi_null.h. See ubi_null.h for more info.
76
* Revision 4.0 1998/03/10 03:41:33 crh
77
* Minor comment changes. The revision number is now 4.0 to match the
78
* BinTree and AVLtree modules.
80
* Revision 2.7 1998/01/24 06:37:08 crh
81
* Added a URL for more information.
83
* Revision 2.6 1997/12/23 04:01:12 crh
84
* In this version, all constants & macros defined in the header file have
85
* the ubi_tr prefix. Also cleaned up anything that gcc complained about
86
* when run with '-pedantic -fsyntax-only -Wall'.
88
* Revision 2.5 1997/07/26 04:15:42 crh
89
* + Cleaned up a few minor syntax annoyances that gcc discovered for me.
90
* + Changed ubi_TRUE and ubi_FALSE to ubi_trTRUE and ubi_trFALSE.
92
* Revision 2.4 1997/06/03 04:42:21 crh
93
* Changed TRUE and FALSE to ubi_TRUE and ubi_FALSE to avoid causing
96
* Revision 2.3 1995/10/03 22:19:07 CRH
98
* Also, added the function ubi_sptSplay().
100
* Revision 2.1 95/03/09 23:54:42 CRH
101
* Added the ModuleID static string and function. These modules are now
104
* Revision 2.0 95/02/27 22:34:46 CRH
105
* This module was updated to match the interface changes made to the
106
* ubi_BinTree module. In particular, the interface to the Locate() function
107
* has changed. See ubi_BinTree for more information on changes and new
110
* The revision number was also upped to match ubi_BinTree.
112
* Revision 1.1 93/10/18 20:35:16 CRH
113
* I removed the hard-coded logical device names from the include file
114
* specifications. CRH
116
* Revision 1.0 93/10/15 23:00:15 CRH
117
* With this revision, I have added a set of #define's that provide a single,
118
* standard API to all existing tree modules. Until now, each of the three
119
* existing modules had a different function and typedef prefix, as follows:
123
* ubi_AVLtree ubi_avl
124
* ubi_SplayTree ubi_spt
126
* To further complicate matters, only those portions of the base module
127
* (ubi_BinTree) that were superceeded in the new module had the new names.
128
* For example, if you were using ubi_SplayTree, the locate function was
129
* called "ubi_sptLocate", but the next and previous functions remained
130
* "ubi_btNext" and "ubi_btPrev".
132
* This was not too terrible if you were familiar with the modules and knew
133
* exactly which tree model you wanted to use. If you wanted to be able to
134
* change modules (for speed comparisons, etc), things could get messy very
137
* So, I have added a set of defined names that get redefined in any of the
138
* descendant modules. To use this standardized interface in your code,
139
* simply replace all occurances of "ubi_bt", "ubi_avl", and "ubi_spt" with
140
* "ubi_tr". The "ubi_tr" names will resolve to the correct function or
141
* datatype names for the module that you are using. Just remember to
142
* include the header for that module in your program file. Because these
143
* names are handled by the preprocessor, there is no added run-time
146
* Note that the original names do still exist, and can be used if you wish
147
* to write code directly to a specific module. This should probably only be
148
* done if you are planning to implement a new descendant type, such as
149
* red/black trees. CRH
151
* Revision 0.1 93/04/25 22:03:32 CRH
152
* Simply changed the <exec/types.h> #include reference the .c file to
153
* use <stdlib.h> instead. The latter is portable, the former is not.
155
* Revision 0.0 93/04/21 23:05:52 CRH
156
* Initial version, written by Christopher R. Hertel.
157
* This module implements Splay Trees using the ubi_BinTree module as a basis.
159
* ========================================================================== **
162
#include "ubi_SplayTree.h" /* Header for THIS module. */
164
/* ========================================================================== **
168
static char ModuleID[] = "ubi_SplayTree\n\
170
\tDate: 2000/01/08 23:26:49 \n\
174
/* ========================================================================== **
175
* Private functions...
178
static void Rotate( ubi_btNodePtr p )
179
/* ------------------------------------------------------------------------ **
180
* This function performs a single rotation, moving node *p up one level
183
* Input: p - a pointer to an ubi_btNode in a tree.
187
* Notes: This implements a single rotation in either direction (left
188
* or right). This is the basic building block of all splay
190
* ------------------------------------------------------------------------ **
193
ubi_btNodePtr parentp;
198
parentp = p->Link[ubi_trPARENT]; /* Find parent. */
200
if( parentp ) /* If no parent, then we're already the root. */
203
revway = ubi_trRevWay(way);
204
tmp = p->Link[(int)revway];
206
parentp->Link[(int)way] = tmp;
209
tmp->Link[ubi_trPARENT] = parentp;
213
tmp = parentp->Link[ubi_trPARENT];
214
p->Link[ubi_trPARENT] = tmp;
215
p->gender = parentp->gender;
217
tmp->Link[(int)(p->gender)] = p;
219
parentp->Link[ubi_trPARENT] = p;
220
parentp->gender = revway;
221
p->Link[(int)revway] = parentp;
225
static ubi_btNodePtr Splay( ubi_btNodePtr SplayWithMe )
226
/* ------------------------------------------------------------------------ **
227
* Move the node indicated by SplayWithMe to the root of the tree by
230
* Input: SplayWithMe - A pointer to an ubi_btNode within a tree.
232
* Output: A pointer to the root of the splay tree (i.e., the same as
234
* ------------------------------------------------------------------------ **
237
ubi_btNodePtr parent;
239
while( NULL != (parent = SplayWithMe->Link[ubi_trPARENT]) )
241
if( parent->gender == SplayWithMe->gender ) /* Zig-Zig */
245
if( ubi_trEQUAL != parent->gender ) /* Zig-Zag */
246
Rotate( SplayWithMe );
248
Rotate( SplayWithMe ); /* Zig */
250
return( SplayWithMe );
253
/* ========================================================================== **
254
* Exported utilities.
257
ubi_trBool ubi_sptInsert( ubi_btRootPtr RootPtr,
258
ubi_btNodePtr NewNode,
259
ubi_btItemPtr ItemPtr,
260
ubi_btNodePtr *OldNode )
261
/* ------------------------------------------------------------------------ **
262
* This function uses a non-recursive algorithm to add a new element to the
265
* Input: RootPtr - a pointer to the ubi_btRoot structure that indicates
266
* the root of the tree to which NewNode is to be added.
267
* NewNode - a pointer to an ubi_btNode structure that is NOT
269
* ItemPtr - A pointer to the sort key that is stored within
270
* *NewNode. ItemPtr MUST point to information stored
271
* in *NewNode or an EXACT DUPLICATE. The key data
272
* indicated by ItemPtr is used to place the new node
274
* OldNode - a pointer to an ubi_btNodePtr. When searching
275
* the tree, a duplicate node may be found. If
276
* duplicates are allowed, then the new node will
277
* be simply placed into the tree. If duplicates
278
* are not allowed, however, then one of two things
280
* 1) if overwritting *is not* allowed, this
281
* function will return FALSE (indicating that
282
* the new node could not be inserted), and
283
* *OldNode will point to the duplicate that is
285
* 2) if overwritting *is* allowed, then this
286
* function will swap **OldNode for *NewNode.
287
* In this case, *OldNode will point to the node
288
* that was removed (thus allowing you to free
290
* ** If you are using overwrite mode, ALWAYS **
291
* ** check the return value of this parameter! **
292
* Note: You may pass NULL in this parameter, the
293
* function knows how to cope. If you do this,
294
* however, there will be no way to return a
295
* pointer to an old (ie. replaced) node (which is
296
* a problem if you are using overwrite mode).
298
* Output: a boolean value indicating success or failure. The function
299
* will return FALSE if the node could not be added to the tree.
300
* Such failure will only occur if duplicates are not allowed,
301
* nodes cannot be overwritten, AND a duplicate key was found
303
* ------------------------------------------------------------------------ **
306
ubi_btNodePtr OtherP;
311
if( ubi_btInsert( RootPtr, NewNode, ItemPtr, OldNode ) )
313
RootPtr->root = Splay( NewNode );
314
return( ubi_trTRUE );
317
/* Splay the unreplacable, duplicate keyed, unique, old node. */
318
RootPtr->root = Splay( (*OldNode) );
319
return( ubi_trFALSE );
320
} /* ubi_sptInsert */
322
ubi_btNodePtr ubi_sptRemove( ubi_btRootPtr RootPtr, ubi_btNodePtr DeadNode )
323
/* ------------------------------------------------------------------------ **
324
* This function removes the indicated node from the tree.
326
* Input: RootPtr - A pointer to the header of the tree that contains
327
* the node to be removed.
328
* DeadNode - A pointer to the node that will be removed.
330
* Output: This function returns a pointer to the node that was removed
331
* from the tree (ie. the same as DeadNode).
333
* Note: The node MUST be in the tree indicated by RootPtr. If not,
334
* strange and evil things will happen to your trees.
335
* ------------------------------------------------------------------------ **
340
(void)Splay( DeadNode ); /* Move dead node to root. */
341
if( NULL != (p = DeadNode->Link[ubi_trLEFT]) )
342
{ /* If left subtree exists... */
343
ubi_btNodePtr q = DeadNode->Link[ubi_trRIGHT];
345
p->Link[ubi_trPARENT] = NULL; /* Left subtree node becomes root.*/
346
p->gender = ubi_trPARENT;
347
p = ubi_btLast( p ); /* Find rightmost left node... */
348
p->Link[ubi_trRIGHT] = q; /* ...attach right tree. */
350
q->Link[ubi_trPARENT] = p;
351
RootPtr->root = Splay( p ); /* Resplay at p. */
355
if( NULL != (p = DeadNode->Link[ubi_trRIGHT]) )
356
{ /* No left, but right subtree exists... */
357
p->Link[ubi_trPARENT] = NULL; /* Right subtree root becomes... */
358
p->gender = ubi_trPARENT; /* ...overall tree root. */
362
RootPtr->root = NULL; /* No subtrees => empty tree. */
365
(RootPtr->count)--; /* Decrement node count. */
366
return( DeadNode ); /* Return pointer to pruned node. */
367
} /* ubi_sptRemove */
369
ubi_btNodePtr ubi_sptLocate( ubi_btRootPtr RootPtr,
370
ubi_btItemPtr FindMe,
371
ubi_trCompOps CompOp )
372
/* ------------------------------------------------------------------------ **
373
* The purpose of ubi_btLocate() is to find a node or set of nodes given
374
* a target value and a "comparison operator". The Locate() function is
375
* more flexible and (in the case of trees that may contain dupicate keys)
376
* more precise than the ubi_btFind() function. The latter is faster,
377
* but it only searches for exact matches and, if the tree contains
378
* duplicates, Find() may return a pointer to any one of the duplicate-
382
* RootPtr - A pointer to the header of the tree to be searched.
383
* FindMe - An ubi_btItemPtr that indicates the key for which to
385
* CompOp - One of the following:
386
* CompOp Return a pointer to the node with
387
* ------ ---------------------------------
388
* ubi_trLT - the last key value that is less
390
* ubi_trLE - the first key matching FindMe, or
391
* the last key that is less than
393
* ubi_trEQ - the first key matching FindMe.
394
* ubi_trGE - the first key matching FindMe, or the
395
* first key greater than FindMe.
396
* ubi_trGT - the first key greater than FindMe.
398
* A pointer to the node matching the criteria listed above under
399
* CompOp, or NULL if no node matched the criteria.
402
* In the case of trees with duplicate keys, Locate() will behave as
406
* Keys: 1 2 2 2 3 3 3 3 3 4 4 Keys: 1 1 2 2 2 4 4 5 5 5 6
410
* That is, when returning a pointer to a node with a key that is LESS
411
* THAN the target key (FindMe), Locate() will return a pointer to the
412
* LAST matching node.
413
* When returning a pointer to a node with a key that is GREATER
414
* THAN the target key (FindMe), Locate() will return a pointer to the
415
* FIRST matching node.
417
* See Also: ubi_btFind(), ubi_btFirstOf(), ubi_btLastOf().
418
* ------------------------------------------------------------------------ **
423
p = ubi_btLocate( RootPtr, FindMe, CompOp );
425
RootPtr->root = Splay( p );
427
} /* ubi_sptLocate */
429
ubi_btNodePtr ubi_sptFind( ubi_btRootPtr RootPtr,
430
ubi_btItemPtr FindMe )
431
/* ------------------------------------------------------------------------ **
432
* This function performs a non-recursive search of a tree for any node
433
* matching a specific key.
436
* RootPtr - a pointer to the header of the tree to be searched.
437
* FindMe - a pointer to the key value for which to search.
440
* A pointer to a node with a key that matches the key indicated by
441
* FindMe, or NULL if no such node was found.
443
* Note: In a tree that allows duplicates, the pointer returned *might
444
* not* point to the (sequentially) first occurance of the
445
* desired key. In such a tree, it may be more useful to use
447
* ------------------------------------------------------------------------ **
452
p = ubi_btFind( RootPtr, FindMe );
454
RootPtr->root = Splay( p );
458
void ubi_sptSplay( ubi_btRootPtr RootPtr,
459
ubi_btNodePtr SplayMe )
460
/* ------------------------------------------------------------------------ **
461
* This function allows you to splay the tree at a given node, thus moving
462
* the node to the top of the tree.
465
* RootPtr - a pointer to the header of the tree to be splayed.
466
* SplayMe - a pointer to a node within the tree. This will become
470
* Notes: This is an uncharacteristic function for this group of modules
471
* in that it provides access to the internal balancing routines,
472
* which would normally be hidden.
473
* Splaying the tree will not damage it (assuming that I've done
474
* *my* job), but there is overhead involved. I don't recommend
475
* that you use this function unless you understand the underlying
476
* Splay Tree principles involved.
477
* ------------------------------------------------------------------------ **
480
RootPtr->root = Splay( SplayMe );
483
int ubi_sptModuleID( int size, char *list[] )
484
/* ------------------------------------------------------------------------ **
485
* Returns a set of strings that identify the module.
487
* Input: size - The number of elements in the array <list>.
488
* list - An array of pointers of type (char *). This array
489
* should, initially, be empty. This function will fill
490
* in the array with pointers to strings.
491
* Output: The number of elements of <list> that were used. If this value
492
* is less than <size>, the values of the remaining elements are
495
* Notes: Please keep in mind that the pointers returned indicate strings
496
* stored in static memory. Don't free() them, don't write over
497
* them, etc. Just read them.
498
* ------------------------------------------------------------------------ **
505
return( 1 + ubi_btModuleID( --size, &(list[1]) ) );
509
} /* ubi_sptModuleID */
511
/* ================================ The End ================================= */