static void Main(string[] args)
{
// 1
// 5 7
// 2 3 9 11
Node <int> root = new Node <int>(1,
new Node <int>(5,
new Node <int>(2),
new Node <int>(3)),
new Node <int>(7,
new Node <int>(9),
new Node <int>(11))
);
BinaryTree <int> tree = new BinaryTree <int>(root);
Console.WriteLine(tree.DFSPreorder(tree.Root, 0));
Console.WriteLine();
Console.WriteLine();
Console.WriteLine(tree.DFSInOrder(tree.Root, 0));
Console.WriteLine();
Console.WriteLine();
Console.WriteLine(tree.DFSPostorder(tree.Root, 0));
}