/* Rebalance sub-tree whose left branch has become short because of deletion */
AVLNode *
AVL_RebalanceShorterLeft(AVLNode * self, int *height_changed)
{
#ifndef __CXC__
AVLNode *p = self;
#else
AVLNode *p;
p = self;
#endif
switch (p->balance) {
case Equal:
p->balance = RightHigh;
*height_changed = 0;
break;
case LeftHigh:
/* taller (left) subtree was shortened */
p->balance = Equal;
break;
case RightHigh:
{
/*
* shorter (left) subtree was shortened, violating
* AVL rules
*/
AVLNode *q;
q = p->right;
switch (q->balance) {
case Equal:
*height_changed = 0;
q->balance = LeftHigh;
p = AVL_RotateLeft(p);
break;
case RightHigh:
p->balance = q->balance = Equal;
p = AVL_RotateLeft(p);
break;
case LeftHigh:
p = AVL_DoubleRotateLeft(p);
break;
}
break;
}
}
return p;
}
treenode *AVL_RightBalance(treenode * r)
{
treenode *x;
treenode *w;
x = r->Rchild;
switch (x->bf) {
case RH:
r->bf = EH;
x->bf = EH;
r = AVL_RotateLeft(r);
break;
#ifdef AVL_DEBUG
case EH:
Error(5);
break;
#endif
case LH:
w = x->Lchild;
switch (w->bf) {
case EH:
r->bf = EH;
x->bf = EH;
break;
case LH:
r->bf = EH;
x->bf = RH;
break;
case RH:
r->bf = LH;
x->bf = EH;
break;
}
w->bf = EH;
x = AVL_RotateRight(x);
r->Rchild = x;
r = AVL_RotateLeft(r);
}
return r;
}
/*
* Rebalance sub-tree whose right branch has become heavier because of
* insertion
*/
AVLNode *
AVL_RebalanceHeavierRight(AVLNode * self, int *height_changed)
{
#ifndef __CXC__
AVLNode *root = self;
#else
AVLNode *root;
root = self;
#endif
/* right-subtree has grown by one level */
switch (root->balance) {
case LeftHigh:
root->balance = Equal;
*height_changed = 0;
break;
case Equal:
root->balance = RightHigh;
break;
case RightHigh:
{
#ifndef __CXC__
AVLNode *rt = self->right;
#else
AVLNode *rt;
rt = self->right;
#endif
switch (rt->balance) {
case RightHigh:
self->balance = Equal;
rt->balance = Equal;
root = AVL_RotateLeft(self);
break;
case LeftHigh:
root = AVL_DoubleRotateLeft(self);
break;
default:
break;
}
*height_changed = 0;
break;
}
}
return root;
}
/* doubly rotate sub-tree and return new root (change balance as needed) */
AVLNode *
AVL_DoubleRotateLeft(AVLNode * self)
{
#ifndef __CXC__
AVLNode *rt = self->right;
AVLNode *lf = rt->left;
AVLNode *root;
#else
AVLNode *rt;
AVLNode *lf;
AVLNode *root;
rt = self->right;
lf = rt->left;
#endif
switch (lf->balance) {
case RightHigh:
self->balance = LeftHigh;
rt->balance = Equal;
break;
case Equal:
self->balance = rt->balance = Equal;
break;
case LeftHigh:
self->balance = Equal;
rt->balance = RightHigh;
break;
}
lf->balance = Equal;
AVL_SetRight(self, AVL_RotateRight(rt));
root = AVL_RotateLeft(self);
return root;
}
