AVLNode RotateR(AVLNode u)
{
var v = u.Left;
Replace(u, v);
u.Left = v.Right;
v.Right.Parent = u;
v.Right = u;
u.Parent = v;
u.Adjust();
v.Adjust();
return(v);
}
AVLNode RotateL(AVLNode v)
{
var u = v.Right;
Replace(v, u);
v.Right = u.Left;
u.Left.Parent = v;
u.Left = v;
v.Parent = u;
v.Adjust();
u.Adjust();
return(u);
}