func (bst *BST) Root() *Node {
	return bst.root
}
Root returns the root node of a BST.
package bst
import "fmt"
type Node struct {
	Val                 int
	Parent, Left, Right *Node
}
type BST struct {
	root *Node
	size int
}
func NewBST() *BST {
	return &BST{size: 0}
}
func (bst *BST) Cardinality() int {
	return bst.size
}
func (bst *BST) IsEmpty() bool {
	return bst.Cardinality() == 0
}