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Replace avl_insert/delete with iterative version
This commit is contained in:
Howard Chu
parent
53833c6ae6
commit
dee98ccd47
@ -27,6 +27,7 @@
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* This work was originally developed by the University of Michigan
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* (as part of U-MICH LDAP). Additional significant contributors
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* include:
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* Howard Y. Chu
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* Hallvard B. Furuseth
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* Kurt D. Zeilenga
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*/
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@ -47,170 +48,7 @@
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#define AVL_INTERNAL
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#include "avl.h"
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#define ROTATERIGHT(x) { \
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Avlnode *tmp;\
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if ( *(x) == NULL || (*(x))->avl_left == NULL ) {\
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(void) fputs("RR error\n", stderr); exit( EXIT_FAILURE ); \
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}\
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tmp = (*(x))->avl_left;\
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(*(x))->avl_left = tmp->avl_right;\
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tmp->avl_right = *(x);\
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*(x) = tmp;\
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}
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#define ROTATELEFT(x) { \
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Avlnode *tmp;\
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if ( *(x) == NULL || (*(x))->avl_right == NULL ) {\
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(void) fputs("RL error\n", stderr); exit( EXIT_FAILURE ); \
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}\
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tmp = (*(x))->avl_right;\
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(*(x))->avl_right = tmp->avl_left;\
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tmp->avl_left = *(x);\
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*(x) = tmp;\
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}
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/*
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* ravl_insert - called from avl_insert() to do a recursive insert into
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* and balance of an avl tree.
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*/
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static int
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ravl_insert(
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Avlnode **iroot,
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void* data,
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int *taller,
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AVL_CMP fcmp, /* comparison function */
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AVL_DUP fdup, /* function to call for duplicates */
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int depth
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)
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{
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int rc, cmp, tallersub;
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Avlnode *l, *r;
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if ( *iroot == 0 ) {
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if ( (*iroot = (Avlnode *) ber_memalloc( sizeof( Avlnode ) ))
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== NULL ) {
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return( -1 );
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}
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(*iroot)->avl_left = 0;
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(*iroot)->avl_right = 0;
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(*iroot)->avl_bf = 0;
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(*iroot)->avl_data = data;
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*taller = 1;
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return( 0 );
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}
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cmp = (*fcmp)( data, (*iroot)->avl_data );
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/* equal - duplicate name */
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if ( cmp == 0 ) {
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*taller = 0;
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return( (*fdup)( (*iroot)->avl_data, data ) );
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}
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/* go right */
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else if ( cmp > 0 ) {
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rc = ravl_insert( &((*iroot)->avl_right), data, &tallersub,
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fcmp, fdup, depth );
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if ( tallersub )
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switch ( (*iroot)->avl_bf ) {
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case LH : /* left high - balance is restored */
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(*iroot)->avl_bf = EH;
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*taller = 0;
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break;
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case EH : /* equal height - now right heavy */
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(*iroot)->avl_bf = RH;
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*taller = 1;
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break;
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case RH : /* right heavy to start - right balance */
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r = (*iroot)->avl_right;
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switch ( r->avl_bf ) {
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case LH : /* double rotation left */
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l = r->avl_left;
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switch ( l->avl_bf ) {
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case LH : (*iroot)->avl_bf = EH;
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r->avl_bf = RH;
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break;
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case EH : (*iroot)->avl_bf = EH;
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r->avl_bf = EH;
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break;
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case RH : (*iroot)->avl_bf = LH;
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r->avl_bf = EH;
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break;
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}
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l->avl_bf = EH;
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ROTATERIGHT( (&r) )
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(*iroot)->avl_right = r;
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ROTATELEFT( iroot )
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*taller = 0;
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break;
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case EH : /* This should never happen */
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break;
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case RH : /* single rotation left */
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(*iroot)->avl_bf = EH;
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r->avl_bf = EH;
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ROTATELEFT( iroot )
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*taller = 0;
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break;
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}
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break;
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}
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else
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*taller = 0;
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}
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/* go left */
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else {
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rc = ravl_insert( &((*iroot)->avl_left), data, &tallersub,
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fcmp, fdup, depth );
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if ( tallersub )
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switch ( (*iroot)->avl_bf ) {
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case LH : /* left high to start - left balance */
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l = (*iroot)->avl_left;
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switch ( l->avl_bf ) {
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case LH : /* single rotation right */
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(*iroot)->avl_bf = EH;
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l->avl_bf = EH;
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ROTATERIGHT( iroot )
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*taller = 0;
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break;
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case EH : /* this should never happen */
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break;
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case RH : /* double rotation right */
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r = l->avl_right;
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switch ( r->avl_bf ) {
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case LH : (*iroot)->avl_bf = RH;
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l->avl_bf = EH;
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break;
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case EH : (*iroot)->avl_bf = EH;
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l->avl_bf = EH;
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break;
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case RH : (*iroot)->avl_bf = EH;
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l->avl_bf = LH;
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break;
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}
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r->avl_bf = EH;
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ROTATELEFT( (&l) )
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(*iroot)->avl_left = l;
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ROTATERIGHT( iroot )
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*taller = 0;
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break;
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}
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break;
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case EH : /* equal height - now left heavy */
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(*iroot)->avl_bf = LH;
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*taller = 1;
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break;
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case RH : /* right high - balance is restored */
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(*iroot)->avl_bf = EH;
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*taller = 0;
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break;
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}
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else
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*taller = 0;
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}
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return( rc );
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}
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static const int avl_bfs[] = {LH, RH};
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/*
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* avl_insert -- insert a node containing data data into the avl tree
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@ -227,245 +65,285 @@ ravl_insert(
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*
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* NOTE: this routine may malloc memory
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*/
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int
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avl_insert( Avlnode **root, void* data, AVL_CMP fcmp, AVL_DUP fdup )
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avl_insert( Avlnode ** root, void *data, AVL_CMP fcmp, AVL_DUP fdup )
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{
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int taller;
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Avlnode *t, *p, *s, *q, *r;
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int a, cmp, ncmp;
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return( ravl_insert( root, data, &taller, fcmp, fdup, 0 ) );
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}
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/*
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* right_balance() - called from delete when root's right subtree has
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* been shortened because of a deletion.
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*/
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static int
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right_balance( Avlnode **root )
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{
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int shorter = -1;
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Avlnode *r, *l;
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switch( (*root)->avl_bf ) {
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case RH: /* was right high - equal now */
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(*root)->avl_bf = EH;
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shorter = 1;
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break;
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case EH: /* was equal - left high now */
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(*root)->avl_bf = LH;
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shorter = 0;
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break;
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case LH: /* was right high - balance */
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l = (*root)->avl_left;
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switch ( l->avl_bf ) {
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case RH : /* double rotation left */
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r = l->avl_right;
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switch ( r->avl_bf ) {
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case RH :
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(*root)->avl_bf = EH;
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l->avl_bf = LH;
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break;
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case EH :
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(*root)->avl_bf = EH;
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l->avl_bf = EH;
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break;
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case LH :
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(*root)->avl_bf = RH;
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l->avl_bf = EH;
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break;
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}
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r->avl_bf = EH;
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ROTATELEFT( (&l) )
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(*root)->avl_left = l;
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ROTATERIGHT( root )
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shorter = 1;
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break;
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case EH : /* right rotation */
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(*root)->avl_bf = LH;
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l->avl_bf = RH;
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ROTATERIGHT( root );
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shorter = 0;
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break;
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case LH : /* single rotation right */
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(*root)->avl_bf = EH;
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l->avl_bf = EH;
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ROTATERIGHT( root )
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shorter = 1;
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break;
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if ( *root == NULL ) {
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if (( r = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
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return( -1 );
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}
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break;
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}
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r->avl_link[0] = r->avl_link[1] = NULL;
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r->avl_data = data;
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r->avl_bf = EH;
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*root = r;
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return( shorter );
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}
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/*
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* left_balance() - called from delete when root's left subtree has
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* been shortened because of a deletion.
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*/
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static int
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left_balance( Avlnode **root )
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{
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int shorter = -1;
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Avlnode *r, *l;
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switch( (*root)->avl_bf ) {
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case LH: /* was left high - equal now */
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(*root)->avl_bf = EH;
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shorter = 1;
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break;
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case EH: /* was equal - right high now */
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(*root)->avl_bf = RH;
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shorter = 0;
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break;
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case RH: /* was right high - balance */
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r = (*root)->avl_right;
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switch ( r->avl_bf ) {
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case LH : /* double rotation left */
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l = r->avl_left;
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switch ( l->avl_bf ) {
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case LH :
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(*root)->avl_bf = EH;
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r->avl_bf = RH;
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break;
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case EH :
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(*root)->avl_bf = EH;
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r->avl_bf = EH;
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break;
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case RH :
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(*root)->avl_bf = LH;
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r->avl_bf = EH;
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break;
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}
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l->avl_bf = EH;
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ROTATERIGHT( (&r) )
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(*root)->avl_right = r;
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ROTATELEFT( root )
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shorter = 1;
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break;
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case EH : /* single rotation left */
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(*root)->avl_bf = RH;
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r->avl_bf = LH;
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ROTATELEFT( root );
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shorter = 0;
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break;
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case RH : /* single rotation left */
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(*root)->avl_bf = EH;
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r->avl_bf = EH;
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ROTATELEFT( root )
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shorter = 1;
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break;
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}
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break;
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}
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return( shorter );
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}
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/*
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* ravl_delete() - called from avl_delete to do recursive deletion of a
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* node from an avl tree. It finds the node recursively, deletes it,
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* and returns shorter if the tree is shorter after the deletion and
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* rebalancing.
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*/
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static void*
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ravl_delete( Avlnode **root, void* data, AVL_CMP fcmp, int *shorter )
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{
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int shortersubtree = 0;
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int cmp;
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void* savedata;
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Avlnode *minnode, *savenode;
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if ( *root == NULLAVL )
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return( 0 );
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cmp = (*fcmp)( data, (*root)->avl_data );
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/* found it! */
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if ( cmp == 0 ) {
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savenode = *root;
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savedata = savenode->avl_data;
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/* simple cases: no left child */
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if ( (*root)->avl_left == 0 ) {
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*root = (*root)->avl_right;
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*shorter = 1;
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ber_memfree( (char *) savenode );
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return( savedata );
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/* no right child */
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} else if ( (*root)->avl_right == 0 ) {
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*root = (*root)->avl_left;
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*shorter = 1;
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ber_memfree( (char *) savenode );
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return( savedata );
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}
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/*
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* avl_getmin will return to us the smallest node greater
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* than the one we are trying to delete. deleting this node
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* from the right subtree is guaranteed to end in one of the
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* simple cases above.
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*/
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minnode = (*root)->avl_right;
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while ( minnode->avl_left != NULLAVL )
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minnode = minnode->avl_left;
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/* swap the data */
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(*root)->avl_data = minnode->avl_data;
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minnode->avl_data = savedata;
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savedata = ravl_delete( &(*root)->avl_right, data, fcmp,
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&shortersubtree );
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if ( shortersubtree )
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*shorter = right_balance( root );
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else
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*shorter = 0;
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/* go left */
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} else if ( cmp < 0 ) {
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if ( (savedata = ravl_delete( &(*root)->avl_left, data, fcmp,
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&shortersubtree )) == 0 ) {
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*shorter = 0;
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return( 0 );
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}
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/* left subtree shorter? */
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if ( shortersubtree )
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*shorter = left_balance( root );
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else
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*shorter = 0;
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/* go right */
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} else {
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if ( (savedata = ravl_delete( &(*root)->avl_right, data, fcmp,
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&shortersubtree )) == 0 ) {
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*shorter = 0;
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return( 0 );
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}
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if ( shortersubtree )
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*shorter = right_balance( root );
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else
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*shorter = 0;
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}
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return( savedata );
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}
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t = NULL;
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s = p = *root;
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/*
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* avl_delete() - deletes the node containing data (according to fcmp) from
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* the avl tree rooted at root.
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*/
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/* find insertion point */
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while (1) {
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cmp = fcmp( data, p->avl_data );
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if ( cmp == 0 )
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return (*fdup)( p->avl_data, data );
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cmp = (cmp > 0);
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q = p->avl_link[cmp];
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if (q == NULL) {
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/* insert */
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if (( q = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
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return( -1 );
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}
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q->avl_link[0] = q->avl_link[1] = NULL;
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q->avl_data = data;
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q->avl_bf = EH;
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p->avl_link[cmp] = q;
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break;
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} else if ( q->avl_bf ) {
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t = p;
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s = q;
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}
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p = q;
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}
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/* adjust balance factors */
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cmp = fcmp( data, s->avl_data ) > 0;
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r = p = s->avl_link[cmp];
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a = avl_bfs[cmp];
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while ( p != q ) {
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cmp = fcmp( data, p->avl_data ) > 0;
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p->avl_bf = avl_bfs[cmp];
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p = p->avl_link[cmp];
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}
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/* checks and balances */
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if ( s->avl_bf == EH ) {
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s->avl_bf = a;
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return 0;
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} else if ( s->avl_bf == -a ) {
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s->avl_bf = EH;
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return 0;
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} else if ( s->avl_bf == a ) {
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cmp = (a > 0);
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ncmp = !cmp;
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if ( r->avl_bf == a ) {
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/* single rotation */
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p = r;
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s->avl_link[cmp] = r->avl_link[ncmp];
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r->avl_link[ncmp] = s;
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s->avl_bf = 0;
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r->avl_bf = 0;
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} else if ( r->avl_bf == -a ) {
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/* double rotation */
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p = r->avl_link[ncmp];
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r->avl_link[ncmp] = p->avl_link[cmp];
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p->avl_link[cmp] = r;
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s->avl_link[cmp] = p->avl_link[ncmp];
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p->avl_link[ncmp] = s;
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if ( p->avl_bf == a ) {
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s->avl_bf = -a;
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r->avl_bf = 0;
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} else if ( p->avl_bf == -a ) {
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s->avl_bf = 0;
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r->avl_bf = a;
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} else {
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s->avl_bf = 0;
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r->avl_bf = 0;
|
||||
}
|
||||
p->avl_bf = 0;
|
||||
}
|
||||
/* Update parent */
|
||||
if ( t == NULL )
|
||||
*root = p;
|
||||
else if ( s == t->avl_right )
|
||||
t->avl_right = p;
|
||||
else
|
||||
t->avl_left = p;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
void*
|
||||
avl_delete( Avlnode **root, void* data, AVL_CMP fcmp )
|
||||
{
|
||||
int shorter;
|
||||
Avlnode *p, *q, *r, *top;
|
||||
int side, side_bf, shorter, nside;
|
||||
|
||||
return( ravl_delete( root, data, fcmp, &shorter ) );
|
||||
/* parent stack */
|
||||
Avlnode *pptr[sizeof(void *)*8];
|
||||
unsigned char pdir[sizeof(void *)*8];
|
||||
int depth = 0;
|
||||
|
||||
if ( *root == NULL )
|
||||
return NULL;
|
||||
|
||||
p = *root;
|
||||
|
||||
while (1) {
|
||||
side = fcmp( data, p->avl_data );
|
||||
if ( !side )
|
||||
break;
|
||||
side = ( side > 0 );
|
||||
pdir[depth] = side;
|
||||
pptr[depth++] = p;
|
||||
|
||||
p = p->avl_link[side];
|
||||
if ( p == NULL )
|
||||
return p;
|
||||
}
|
||||
data = p->avl_data;
|
||||
|
||||
/* If this node has two children, swap so we are deleting a node with
|
||||
* at most one child.
|
||||
*/
|
||||
if ( p->avl_link[0] && p->avl_link[1] ) {
|
||||
|
||||
/* find the immediate predecessor <q> */
|
||||
q = p->avl_link[0];
|
||||
side = depth;
|
||||
pdir[depth++] = 0;
|
||||
while (q->avl_link[1]) {
|
||||
pdir[depth] = 1;
|
||||
pptr[depth++] = q;
|
||||
q = q->avl_link[1];
|
||||
}
|
||||
/* swap links */
|
||||
r = p->avl_link[0];
|
||||
p->avl_link[0] = q->avl_link[0];
|
||||
q->avl_link[0] = r;
|
||||
|
||||
q->avl_link[1] = p->avl_link[1];
|
||||
p->avl_link[1] = NULL;
|
||||
|
||||
q->avl_bf = p->avl_bf;
|
||||
|
||||
/* fix stack positions: old parent of p points to q */
|
||||
pptr[side] = q;
|
||||
if ( side ) {
|
||||
--side;
|
||||
r = pptr[side];
|
||||
r->avl_link[pdir[side]] = q;
|
||||
} else {
|
||||
*root = q;
|
||||
}
|
||||
/* new parent of p points to p */
|
||||
if ( depth > 1 ) {
|
||||
r = pptr[depth-1];
|
||||
r->avl_link[1] = p;
|
||||
} else {
|
||||
q->avl_link[0] = p;
|
||||
}
|
||||
}
|
||||
|
||||
/* now <p> has at most one child, get it */
|
||||
q = p->avl_link[0];
|
||||
|
||||
ber_memfree( p );
|
||||
|
||||
if ( !depth ) {
|
||||
*root = q;
|
||||
return data;
|
||||
}
|
||||
|
||||
/* set the child into p's parent */
|
||||
depth--;
|
||||
p = pptr[depth];
|
||||
side = pdir[depth];
|
||||
p->avl_link[side] = q;
|
||||
|
||||
top = NULL;
|
||||
shorter = 1;
|
||||
|
||||
while ( shorter ) {
|
||||
p = pptr[depth];
|
||||
side = pdir[depth];
|
||||
nside = !side;
|
||||
side_bf = avl_bfs[side];
|
||||
|
||||
/* case 1: height unchanged */
|
||||
if ( p->avl_bf == EH ) {
|
||||
/* Tree is now heavier on opposite side */
|
||||
p->avl_bf = avl_bfs[nside];
|
||||
shorter = 0;
|
||||
|
||||
} else if ( p->avl_bf == side_bf ) {
|
||||
/* case 2: taller subtree shortened, height reduced */
|
||||
p->avl_bf = EH;
|
||||
} else {
|
||||
/* case 3: shorter subtree shortened */
|
||||
if ( depth )
|
||||
top = pptr[depth-1]; /* p->parent; */
|
||||
else
|
||||
top = NULL;
|
||||
/* set <q> to the taller of the two subtrees of <p> */
|
||||
q = p->avl_link[nside];
|
||||
if ( q->avl_bf == EH ) {
|
||||
/* case 3a: height unchanged, single rotate */
|
||||
p->avl_link[nside] = q->avl_link[side];
|
||||
q->avl_link[side] = p;
|
||||
shorter = 0;
|
||||
q->avl_bf = side_bf;
|
||||
p->avl_bf = (- side_bf);
|
||||
|
||||
} else if ( q->avl_bf == p->avl_bf ) {
|
||||
/* case 3b: height reduced, single rotate */
|
||||
p->avl_link[nside] = q->avl_link[side];
|
||||
q->avl_link[side] = p;
|
||||
shorter = 1;
|
||||
q->avl_bf = EH;
|
||||
p->avl_bf = EH;
|
||||
|
||||
} else {
|
||||
/* case 3c: height reduced, balance factors opposite */
|
||||
r = q->avl_link[side];
|
||||
q->avl_link[side] = r->avl_link[nside];
|
||||
r->avl_link[nside] = q;
|
||||
|
||||
p->avl_link[nside] = r->avl_link[side];
|
||||
r->avl_link[side] = p;
|
||||
|
||||
if ( r->avl_bf == side_bf ) {
|
||||
q->avl_bf = (- side_bf);
|
||||
p->avl_bf = EH;
|
||||
} else if ( r->avl_bf == (- side_bf)) {
|
||||
q->avl_bf = EH;
|
||||
p->avl_bf = side_bf;
|
||||
} else {
|
||||
q->avl_bf = EH;
|
||||
p->avl_bf = EH;
|
||||
}
|
||||
r->avl_bf = EH;
|
||||
q = r;
|
||||
}
|
||||
/* a rotation has caused <q> (or <r> in case 3c) to become
|
||||
* the root. let <p>'s former parent know this.
|
||||
*/
|
||||
if ( top == NULL ) {
|
||||
*root = q;
|
||||
} else if (top->avl_link[0] == p) {
|
||||
top->avl_link[0] = q;
|
||||
} else {
|
||||
top->avl_link[1] = q;
|
||||
}
|
||||
/* end case 3 */
|
||||
p = q;
|
||||
}
|
||||
if ( !depth )
|
||||
break;
|
||||
depth--;
|
||||
} /* end while(shorter) */
|
||||
|
||||
return data;
|
||||
}
|
||||
|
||||
static int
|
||||
|
||||
Loading…
Reference in New Issue
Block a user