NodePtr Tree::RemoveNode (NodePtr Node)
{
NodePtr result = NULL;
if (Node == Root)
{
if (Leaves == 1)
{
Root = NULL;
Node->SetAnc (NULL);
Leaves = Internals = 0;
}
return result;
}
NodePtr p;
NodePtr Ancestor = Node->GetAnc();
if (Ancestor->GetDegree() == 2)
{
// ancestor is binary, so remove node and its ancestor
if (Node->IsTheChild ())
p = Node->GetSibling();
else
p = Ancestor->GetChild();
NodePtr q = Ancestor->GetAnc();
p->SetAnc (q);
if (q != NULL)
{
if (Ancestor->IsTheChild())
q->SetChild (p);
else
{
NodePtr r = Ancestor->LeftSiblingOf ();
r->SetSibling (p);
}
p->SetSibling (Ancestor->GetSibling());
result = p;
}
else
{
// Ancestor is the root
Root = p;
p->SetSibling (NULL);
result = p;
}
delete Ancestor;
Internals--;
if (Node->IsLeaf())
Leaves--;
Node->SetAnc (NULL);
Node->SetSibling (NULL);
}
else
{
// polytomy, just remove node
NodePtr q;
if (Node->IsTheChild())
{
Ancestor->SetChild (Node->GetSibling());
q = Node->GetSibling ();
}
else
{
q = Node->LeftSiblingOf ();
q->SetSibling (Node->GetSibling ());
}
Node->SetSibling (NULL);
Node->SetAnc (NULL);
if (Node->IsLeaf())
Leaves--;
Ancestor->SetDegree (Ancestor->GetDegree() - 1);
result = q;
}
}
