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510 lines
21 KiB
C
510 lines
21 KiB
C
/* ========================================================================== **
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* ubi_SplayTree.c
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*
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* Copyright (C) 1993-1998 by Christopher R. Hertel
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*
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* Email: crh@ubiqx.mn.org
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* -------------------------------------------------------------------------- **
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*
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* This module implements "splay" trees. Splay trees are binary trees
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* that are rearranged (splayed) whenever a node is accessed. The
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* splaying process *tends* to make the tree bushier (improves balance),
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* and the nodes that are accessed most frequently *tend* to be closer to
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* the top.
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*
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* References: "Self-Adjusting Binary Search Trees", by Daniel Sleator and
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* Robert Tarjan. Journal of the Association for Computing
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* Machinery Vol 32, No. 3, July 1985 pp. 652-686
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*
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* See also: http://www.cs.cmu.edu/~sleator/
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*
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* -------------------------------------------------------------------------- **
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* -------------------------------------------------------------------------- **
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*
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* Log: ubi_SplayTree.c,v
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* Revision 4.4 1998/06/04 21:29:27 crh
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* Upper-cased defined constants (eg UBI_BINTREE_H) in some header files.
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* This is more "standard", and is what people expect. Weird, eh?
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*
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* Revision 4.3 1998/06/03 17:45:05 crh
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* Further fiddling with sys_include.h. It's now in ubi_BinTree.h which is
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* included by all of the binary tree files.
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*
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* Also fixed some warnings produced by lint on Irix 6.2, which doesn't seem
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* to like syntax like this:
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*
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* if( (a = b) )
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*
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* The fix was to change lines like the above to:
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*
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* if( 0 != (a=b) )
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*
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* Which means the same thing.
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*
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* Reminder: Some of the ubi_tr* macros in ubi_BinTree.h are redefined in
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* ubi_AVLtree.h and ubi_SplayTree.h. This allows easy swapping
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* of tree types by simply changing a header. Unfortunately, the
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* macro redefinitions in ubi_AVLtree.h and ubi_SplayTree.h will
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* conflict if used together. You must either choose a single tree
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* type, or use the underlying function calls directly. Compare
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* the two header files for more information.
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*
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* Revision 4.2 1998/06/02 01:29:14 crh
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* Changed ubi_null.h to sys_include.h to make it more generic.
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*
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* Revision 4.1 1998/05/20 04:37:54 crh
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* The C file now includes ubi_null.h. See ubi_null.h for more info.
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*
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* Revision 4.0 1998/03/10 03:41:33 crh
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* Minor comment changes. The revision number is now 4.0 to match the
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* BinTree and AVLtree modules.
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*
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* Revision 2.7 1998/01/24 06:37:08 crh
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* Added a URL for more information.
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*
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* Revision 2.6 1997/12/23 04:01:12 crh
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* In this version, all constants & macros defined in the header file have
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* the ubi_tr prefix. Also cleaned up anything that gcc complained about
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* when run with '-pedantic -fsyntax-only -Wall'.
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*
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* Revision 2.5 1997/07/26 04:15:42 crh
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* + Cleaned up a few minor syntax annoyances that gcc discovered for me.
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* + Changed ubi_TRUE and ubi_FALSE to ubi_trTRUE and ubi_trFALSE.
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*
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* Revision 2.4 1997/06/03 04:42:21 crh
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* Changed TRUE and FALSE to ubi_TRUE and ubi_FALSE to avoid causing
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* problems.
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*
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* Revision 2.3 1995/10/03 22:19:07 CRH
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* Ubisized!
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* Also, added the function ubi_sptSplay().
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*
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* Revision 2.1 95/03/09 23:54:42 CRH
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* Added the ModuleID static string and function. These modules are now
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* self-identifying.
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*
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* Revision 2.0 95/02/27 22:34:46 CRH
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* This module was updated to match the interface changes made to the
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* ubi_BinTree module. In particular, the interface to the Locate() function
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* has changed. See ubi_BinTree for more information on changes and new
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* functions.
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*
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* The revision number was also upped to match ubi_BinTree.
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*
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* Revision 1.1 93/10/18 20:35:16 CRH
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* I removed the hard-coded logical device names from the include file
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* specifications. CRH
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*
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* Revision 1.0 93/10/15 23:00:15 CRH
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* With this revision, I have added a set of #define's that provide a single,
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* standard API to all existing tree modules. Until now, each of the three
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* existing modules had a different function and typedef prefix, as follows:
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*
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* Module Prefix
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* ubi_BinTree ubi_bt
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* ubi_AVLtree ubi_avl
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* ubi_SplayTree ubi_spt
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*
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* To further complicate matters, only those portions of the base module
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* (ubi_BinTree) that were superceeded in the new module had the new names.
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* For example, if you were using ubi_SplayTree, the locate function was
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* called "ubi_sptLocate", but the next and previous functions remained
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* "ubi_btNext" and "ubi_btPrev".
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*
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* This was not too terrible if you were familiar with the modules and knew
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* exactly which tree model you wanted to use. If you wanted to be able to
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* change modules (for speed comparisons, etc), things could get messy very
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* quickly.
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*
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* So, I have added a set of defined names that get redefined in any of the
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* descendant modules. To use this standardized interface in your code,
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* simply replace all occurances of "ubi_bt", "ubi_avl", and "ubi_spt" with
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* "ubi_tr". The "ubi_tr" names will resolve to the correct function or
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* datatype names for the module that you are using. Just remember to
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* include the header for that module in your program file. Because these
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* names are handled by the preprocessor, there is no added run-time
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* overhead.
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*
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* Note that the original names do still exist, and can be used if you wish
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* to write code directly to a specific module. This should probably only be
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* done if you are planning to implement a new descendant type, such as
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* red/black trees. CRH
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*
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* Revision 0.1 93/04/25 22:03:32 CRH
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* Simply changed the <exec/types.h> #include reference the .c file to
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* use <stdlib.h> instead. The latter is portable, the former is not.
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*
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* Revision 0.0 93/04/21 23:05:52 CRH
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* Initial version, written by Christopher R. Hertel.
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* This module implements Splay Trees using the ubi_BinTree module as a basis.
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*
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* ========================================================================== **
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*/
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#include "ubi_SplayTree.h" /* Header for THIS module. */
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/* ========================================================================== **
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* Static data.
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*/
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static char ModuleID[] = "ubi_SplayTree\n\
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\tRevision: 4.4 \n\
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\tDate: 1998/06/04 21:29:27 \n\
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\tAuthor: crh \n";
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/* ========================================================================== **
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* Private functions...
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*/
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static void Rotate( ubi_btNodePtr p )
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/* ------------------------------------------------------------------------ **
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* This function performs a single rotation, moving node *p up one level
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* in the tree.
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*
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* Input: p - a pointer to an ubi_btNode in a tree.
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*
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* Output: None.
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*
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* Notes: This implements a single rotation in either direction (left
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* or right). This is the basic building block of all splay
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* tree rotations.
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr parentp;
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ubi_btNodePtr tmp;
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char way;
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char revway;
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parentp = p->Link[ubi_trPARENT]; /* Find parent. */
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if( parentp ) /* If no parent, then we're already the root. */
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{
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way = p->gender;
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revway = ubi_trRevWay(way);
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tmp = p->Link[(int)revway];
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parentp->Link[(int)way] = tmp;
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if( tmp )
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{
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tmp->Link[ubi_trPARENT] = parentp;
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tmp->gender = way;
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}
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tmp = parentp->Link[ubi_trPARENT];
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p->Link[ubi_trPARENT] = tmp;
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p->gender = parentp->gender;
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if( tmp )
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tmp->Link[(int)(p->gender)] = p;
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parentp->Link[ubi_trPARENT] = p;
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parentp->gender = revway;
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p->Link[(int)revway] = parentp;
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}
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} /* Rotate */
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static ubi_btNodePtr Splay( ubi_btNodePtr SplayWithMe )
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/* ------------------------------------------------------------------------ **
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* Move the node indicated by SplayWithMe to the root of the tree by
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* splaying the tree.
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*
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* Input: SplayWithMe - A pointer to an ubi_btNode within a tree.
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*
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* Output: A pointer to the root of the splay tree (i.e., the same as
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* SplayWithMe).
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr parent;
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while( NULL != (parent = SplayWithMe->Link[ubi_trPARENT]) )
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{
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if( parent->gender == SplayWithMe->gender ) /* Zig-Zig */
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Rotate( parent );
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else
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{
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if( ubi_trEQUAL != parent->gender ) /* Zig-Zag */
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Rotate( SplayWithMe );
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}
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Rotate( SplayWithMe ); /* Zig */
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} /* while */
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return( SplayWithMe );
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} /* Splay */
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/* ========================================================================== **
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* Exported utilities.
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*/
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ubi_trBool ubi_sptInsert( ubi_btRootPtr RootPtr,
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ubi_btNodePtr NewNode,
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ubi_btItemPtr ItemPtr,
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ubi_btNodePtr *OldNode )
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/* ------------------------------------------------------------------------ **
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* This function uses a non-recursive algorithm to add a new element to the
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* splay tree.
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*
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* Input: RootPtr - a pointer to the ubi_btRoot structure that indicates
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* the root of the tree to which NewNode is to be added.
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* NewNode - a pointer to an ubi_btNode structure that is NOT
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* part of any tree.
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* ItemPtr - A pointer to the sort key that is stored within
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* *NewNode. ItemPtr MUST point to information stored
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* in *NewNode or an EXACT DUPLICATE. The key data
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* indicated by ItemPtr is used to place the new node
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* into the tree.
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* OldNode - a pointer to an ubi_btNodePtr. When searching
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* the tree, a duplicate node may be found. If
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* duplicates are allowed, then the new node will
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* be simply placed into the tree. If duplicates
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* are not allowed, however, then one of two things
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* may happen.
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* 1) if overwritting *is not* allowed, this
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* function will return FALSE (indicating that
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* the new node could not be inserted), and
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* *OldNode will point to the duplicate that is
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* still in the tree.
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* 2) if overwritting *is* allowed, then this
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* function will swap **OldNode for *NewNode.
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* In this case, *OldNode will point to the node
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* that was removed (thus allowing you to free
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* the node).
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* ** If you are using overwrite mode, ALWAYS **
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* ** check the return value of this parameter! **
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* Note: You may pass NULL in this parameter, the
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* function knows how to cope. If you do this,
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* however, there will be no way to return a
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* pointer to an old (ie. replaced) node (which is
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* a problem if you are using overwrite mode).
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*
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* Output: a boolean value indicating success or failure. The function
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* will return FALSE if the node could not be added to the tree.
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* Such failure will only occur if duplicates are not allowed,
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* nodes cannot be overwritten, AND a duplicate key was found
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* within the tree.
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr OtherP;
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if( !(OldNode) )
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OldNode = &OtherP;
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if( ubi_btInsert( RootPtr, NewNode, ItemPtr, OldNode ) )
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{
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RootPtr->root = Splay( NewNode );
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return( ubi_trTRUE );
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}
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/* Splay the unreplacable, duplicate keyed, unique, old node. */
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RootPtr->root = Splay( (*OldNode) );
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return( ubi_trFALSE );
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} /* ubi_sptInsert */
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ubi_btNodePtr ubi_sptRemove( ubi_btRootPtr RootPtr, ubi_btNodePtr DeadNode )
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/* ------------------------------------------------------------------------ **
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* This function removes the indicated node from the tree.
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*
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* Input: RootPtr - A pointer to the header of the tree that contains
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* the node to be removed.
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* DeadNode - A pointer to the node that will be removed.
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*
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* Output: This function returns a pointer to the node that was removed
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* from the tree (ie. the same as DeadNode).
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*
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* Note: The node MUST be in the tree indicated by RootPtr. If not,
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* strange and evil things will happen to your trees.
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr p;
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(void)Splay( DeadNode ); /* Move dead node to root. */
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if( NULL != (p = DeadNode->Link[ubi_trLEFT]) )
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{ /* If left subtree exists... */
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ubi_btNodePtr q = DeadNode->Link[ubi_trRIGHT];
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p->Link[ubi_trPARENT] = NULL; /* Left subtree node becomes root.*/
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p->gender = ubi_trPARENT;
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p = ubi_btLast( p ); /* Find rightmost left node... */
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p->Link[ubi_trRIGHT] = q; /* ...attach right tree. */
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if( q )
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q->Link[ubi_trPARENT] = p;
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RootPtr->root = Splay( p ); /* Resplay at p. */
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}
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else
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{
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if( NULL != (p = DeadNode->Link[ubi_trRIGHT]) )
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{ /* No left, but right subtree exists... */
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p->Link[ubi_trPARENT] = NULL; /* Right subtree root becomes... */
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p->gender = ubi_trPARENT; /* ...overall tree root. */
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RootPtr->root = p;
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}
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else
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RootPtr->root = NULL; /* No subtrees => empty tree. */
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}
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(RootPtr->count)--; /* Decrement node count. */
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return( DeadNode ); /* Return pointer to pruned node. */
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} /* ubi_sptRemove */
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ubi_btNodePtr ubi_sptLocate( ubi_btRootPtr RootPtr,
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ubi_btItemPtr FindMe,
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ubi_trCompOps CompOp )
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/* ------------------------------------------------------------------------ **
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* The purpose of ubi_btLocate() is to find a node or set of nodes given
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* a target value and a "comparison operator". The Locate() function is
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* more flexible and (in the case of trees that may contain dupicate keys)
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* more precise than the ubi_btFind() function. The latter is faster,
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* but it only searches for exact matches and, if the tree contains
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* duplicates, Find() may return a pointer to any one of the duplicate-
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* keyed records.
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*
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* Input:
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* RootPtr - A pointer to the header of the tree to be searched.
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* FindMe - An ubi_btItemPtr that indicates the key for which to
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* search.
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* CompOp - One of the following:
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* CompOp Return a pointer to the node with
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* ------ ---------------------------------
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* ubi_trLT - the last key value that is less
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* than FindMe.
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* ubi_trLE - the first key matching FindMe, or
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* the last key that is less than
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* FindMe.
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* ubi_trEQ - the first key matching FindMe.
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* ubi_trGE - the first key matching FindMe, or the
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* first key greater than FindMe.
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* ubi_trGT - the first key greater than FindMe.
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* Output:
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* A pointer to the node matching the criteria listed above under
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* CompOp, or NULL if no node matched the criteria.
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*
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* Notes:
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* In the case of trees with duplicate keys, Locate() will behave as
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* follows:
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*
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* Find: 3 Find: 3
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* Keys: 1 2 2 2 3 3 3 3 3 4 4 Keys: 1 1 2 2 2 4 4 5 5 5 6
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* ^ ^ ^ ^ ^
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* LT EQ GT LE GE
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*
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* That is, when returning a pointer to a node with a key that is LESS
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* THAN the target key (FindMe), Locate() will return a pointer to the
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* LAST matching node.
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* When returning a pointer to a node with a key that is GREATER
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* THAN the target key (FindMe), Locate() will return a pointer to the
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* FIRST matching node.
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*
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* See Also: ubi_btFind(), ubi_btFirstOf(), ubi_btLastOf().
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr p;
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p = ubi_btLocate( RootPtr, FindMe, CompOp );
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if( p )
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RootPtr->root = Splay( p );
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return( p );
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} /* ubi_sptLocate */
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ubi_btNodePtr ubi_sptFind( ubi_btRootPtr RootPtr,
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ubi_btItemPtr FindMe )
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/* ------------------------------------------------------------------------ **
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* This function performs a non-recursive search of a tree for any node
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* matching a specific key.
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*
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* Input:
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* RootPtr - a pointer to the header of the tree to be searched.
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* FindMe - a pointer to the key value for which to search.
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*
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* Output:
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* A pointer to a node with a key that matches the key indicated by
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* FindMe, or NULL if no such node was found.
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*
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* Note: In a tree that allows duplicates, the pointer returned *might
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* not* point to the (sequentially) first occurance of the
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* desired key. In such a tree, it may be more useful to use
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* ubi_sptLocate().
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* ------------------------------------------------------------------------ **
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*/
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{
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ubi_btNodePtr p;
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p = ubi_btFind( RootPtr, FindMe );
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if( p )
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RootPtr->root = Splay( p );
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return( p );
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} /* ubi_sptFind */
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void ubi_sptSplay( ubi_btRootPtr RootPtr,
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ubi_btNodePtr SplayMe )
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/* ------------------------------------------------------------------------ **
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* This function allows you to splay the tree at a given node, thus moving
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* the node to the top of the tree.
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*
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* Input:
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* RootPtr - a pointer to the header of the tree to be splayed.
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* SplayMe - a pointer to a node within the tree. This will become
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* the new root node.
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* Output: None.
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*
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* Notes: This is an uncharacteristic function for this group of modules
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* in that it provides access to the internal balancing routines,
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* which would normally be hidden.
|
|
* Splaying the tree will not damage it (assuming that I've done
|
|
* *my* job), but there is overhead involved. I don't recommend
|
|
* that you use this function unless you understand the underlying
|
|
* Splay Tree principles involved.
|
|
* ------------------------------------------------------------------------ **
|
|
*/
|
|
{
|
|
RootPtr->root = Splay( SplayMe );
|
|
} /* ubi_sptSplay */
|
|
|
|
int ubi_sptModuleID( int size, char *list[] )
|
|
/* ------------------------------------------------------------------------ **
|
|
* Returns a set of strings that identify the module.
|
|
*
|
|
* Input: size - The number of elements in the array <list>.
|
|
* list - An array of pointers of type (char *). This array
|
|
* should, initially, be empty. This function will fill
|
|
* in the array with pointers to strings.
|
|
* Output: The number of elements of <list> that were used. If this value
|
|
* is less than <size>, the values of the remaining elements are
|
|
* not guaranteed.
|
|
*
|
|
* Notes: Please keep in mind that the pointers returned indicate strings
|
|
* stored in static memory. Don't free() them, don't write over
|
|
* them, etc. Just read them.
|
|
* ------------------------------------------------------------------------ **
|
|
*/
|
|
{
|
|
if( size > 0 )
|
|
{
|
|
list[0] = ModuleID;
|
|
if( size > 1 )
|
|
return( 1 + ubi_btModuleID( --size, &(list[1]) ) );
|
|
return( 1 );
|
|
}
|
|
return( 0 );
|
|
} /* ubi_sptModuleID */
|
|
|
|
/* ================================ The End ================================= */
|
|
|