func (t *AvlTree) lookupNode(lt c.LookupType, data c.Comparable) (*avlNode, bool) {
if t.root == nil {
return nil, false
}
cn := t.root
for {
r := data.CompareTo(cn.data)
if r == 0 {
return cn, true
}
if r < 0 {
if cn.l == nil {
if lt == c.GTE {
return cn, false
}
return cn.prv, false
}
cn = cn.l
} else {
if cn.r == nil {
if lt == c.LTE {
return cn, false
}
return cn.nxt, false
}
cn = cn.r
}
}
}
func Pair(c1, c2 c.Comparable) Set {
r := c1.CompareTo(c2)
if r == 0 {
return Singleton(c1)
}
if r < 0 {
return &pairSet{x: c1, y: c2}
} else {
return &pairSet{x: c2, y: c1}
}
}
// Insert adds or replaces a value in the tree. If there is already an equal value,
// it is replaced and the old value returned. Otherwise, nil is returned.
func (t *AvlTree) Insert(data c.Comparable) c.Comparable {
if t.root == nil {
t.root = &avlNode{
data: data,
}
t.size++
t.head = t.root
t.tail = t.root
return nil
}
cn := t.root
var r int8
for {
r = data.CompareTo(cn.data)
if r == 0 {
break
}
if r < 0 {
if cn.l == nil {
break
}
cn = cn.l
} else {
if cn.r == nil {
break
}
cn = cn.r
}
}
if r == 0 {
oldData := cn.data
cn.data = data
return oldData
}
nn := &avlNode{
data: data,
p: cn,
}
if r < 0 {
nn.prv = cn.prv
nn.nxt = cn
if cn.prv != nil {
cn.prv.nxt = nn
} else {
t.head = nn
}
cn.prv = nn
cn.l = nn
cn.balance--
} else {
nn.nxt = cn.nxt
nn.prv = cn
if cn.nxt != nil {
cn.nxt.prv = nn
} else {
t.tail = nn
}
cn.nxt = nn
cn.r = nn
cn.balance++
}
t.size++
for {
switch cn.balance {
case 0:
{
// Depth did not increase, we are done.
return nil
}
case -1:
fallthrough
case 1:
{
// Depth increased, propagate.
if cn.p != nil {
if cn.p.l == cn {
cn.p.balance--
} else {
cn.p.balance++
}
cn = cn.p
} else {
return nil // At root, done.
}
}
case -2:
fallthrough
case 2:
{
np, changed := t.rebalanceAtNode(cn)
if changed {
// Change offset the insertion height change, we're done.
return nil
}
cn = np
}
}
}
}
