public static void Main()
{
// Declare new doubly linked list of type int, using Generics<T>.
// Big Oh notated below in Main.
DoublyLinkedList <int> ll = new DoublyLinkedList <int>();
Console.WriteLine("Populate new linked list using AddFirst, AddLast and AddBefore.");
// O(1)
ll.AddFirst(3);
// Create new node to insert.
var n = new Node <int>(7);
// AddLast by node, O(1).
ll.AddLast(n);
// Insert 5 before the 7 node, O(n).
ll.AddBefore(n, 5);
// AddLast by value, O(1).
ll.AddLast(9);
Console.WriteLine("Print:");
ll.Print(); // O(n)
Console.WriteLine("Print Reverse:");
// Print Reverse
ll.PrintReverse(); // O(n)
Console.WriteLine("Remove nodes using RemoveFirst, RemoveLast, Remove(value) methods.");
ll.Remove(7); // O(n)
ll.Print();
ll.RemoveFirst(); // O(1)
ll.Print();
ll.RemoveLast(); // O(1)
ll.Print();
ll.Clear(); // O(1)
Console.WriteLine("Clear linked list.");
Console.WriteLine($"Linked list is Empty: {ll.IsEmpty()}"); // O(1)
}