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Splay the left and right subtrees on min - 1 and max + 1, respectively,

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before trying to coalesce. Forgetting to splay caused us to miss many
opportunities for coalescing.
This commit is contained in:
Tim J. Robbins 2004-07-14 08:33:14 +00:00
parent 6897c4aef7
commit cfab3bdd89
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=132142
1 changed files with 20 additions and 34 deletions
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54
usr.bin/tr/cset.c
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@ -93,29 +93,13 @@ cset_add(struct cset *cs, wchar_t ch)
csn = cs->cs_root = cset_splay(cs->cs_root, ch);
/*
* Easy cases where we can avoid allocating a new node:
* (a) node already exists.
* (b) we can lower the extent's "min" to accomodate this
* character without having to coalesce.
* (c) we can raise the extent's "max" without having
* to coalesce.
* Avoid adding duplicate nodes.
*/
if (cset_rangecmp(csn, ch) == 0)
return (true);
if (ch + 1 == csn->csn_min && (csn->csn_left == NULL ||
ch > csn->csn_left->csn_max + 1)) {
csn->csn_min--;
return (true);
}
if (ch == csn->csn_max + 1 && (csn->csn_right == NULL ||
ch + 1 < csn->csn_right->csn_min)) {
csn->csn_max++;
return (true);
}
/*
* Allocate a new node and link it into the tree as a direct
* child of the root.
* Allocate a new node and make it the new root.
*/
ncsn = malloc(sizeof(*ncsn));
if (ncsn == NULL)
@ -133,24 +117,26 @@ cset_add(struct cset *cs, wchar_t ch)
cs->cs_root = ncsn;
/*
* Splay to bring the newly inserted node to the root, then
* coalesce with left and right neighbours if possible.
* Coalesce with left and right neighbours if possible.
*/
csn = cs->cs_root = cset_splay(cs->cs_root, ch);
if (csn->csn_left != NULL &&
csn->csn_left->csn_max + 1 == csn->csn_min) {
oval = csn->csn_left->csn_min;
cs->cs_root = cset_delete(cs->cs_root,
csn->csn_left->csn_min);
ncsn->csn_min = oval;
if (ncsn->csn_left != NULL) {
ncsn->csn_left = cset_splay(ncsn->csn_left, ncsn->csn_min - 1);
if (ncsn->csn_left->csn_max == ncsn->csn_min - 1) {
oval = ncsn->csn_left->csn_min;
ncsn->csn_left = cset_delete(ncsn->csn_left,
ncsn->csn_left->csn_min);
ncsn->csn_min = oval;
}
}
csn = cs->cs_root = cset_splay(cs->cs_root, ch);
if (csn->csn_right != NULL &&
csn->csn_right->csn_min - 1 == csn->csn_max) {
oval = csn->csn_right->csn_max;
cs->cs_root = cset_delete(cs->cs_root,
csn->csn_right->csn_min);
ncsn->csn_max = oval;
if (ncsn->csn_right != NULL) {
ncsn->csn_right = cset_splay(ncsn->csn_right,
ncsn->csn_max + 1);
if (ncsn->csn_right->csn_min == ncsn->csn_max + 1) {
oval = ncsn->csn_right->csn_max;
ncsn->csn_right = cset_delete(ncsn->csn_right,
ncsn->csn_right->csn_min);
ncsn->csn_max = oval;
}
}
return (true);