//My Code School solution public bool IsBST(BSTNode <int> root) => IsBSTUtil(root, int.MinValue, int.MaxValue);
public void AddNodeRecursive(int x) { var refNode = Root; Root = AddNode(x, refNode); }
public bool IsBinarySearchTree(BSTNode <int> root) { int _value = int.MinValue; return(IsBST(root, ref _value)); }