public static void Main()
{
// Create a new doubly linked list of type int.
DoublyLinkedList <int> dll = new DoublyLinkedList <int>();
Console.WriteLine("Populate new doubly linked list that is NOT a palindrome...");
dll.AddFirst(3);
dll.AddLast(5);
dll.AddLast(7);
dll.AddLast(9);
Console.WriteLine("Print:");
dll.Print();
Console.WriteLine("Print Reverse:");
dll.PrintReverse();
// The IsPalindrome contains 3 methods:
// IsPalindrome: O(2n)
// ReverseAndCopy: O(n), with O(n) space.
// IsEqual: O(n)
// Runtime for IsPalindrome method execution: O(2n) -> O(n)
// with O(n) extra memory.
// Still trying to work in generics, only accepts type int right now.
Console.WriteLine($"Is linked list a palindrome: {dll.IsPalindrome(dll.Head)}");
Console.WriteLine();
Console.WriteLine("Clear linked list.");
dll.Clear();
Console.WriteLine($"Linked list is Empty: {dll.IsEmpty()}");
Console.WriteLine();
Console.WriteLine("Populate new doubly linked list that IS a palindrome...");
dll.AddFirst(3);
dll.AddLast(5);
dll.AddLast(7);
dll.AddLast(5);
dll.AddLast(3);
Console.WriteLine("Print:");
dll.Print();
Console.WriteLine("Print Reverse:");
dll.PrintReverse();
Console.WriteLine($"Is linked list a palindrome: {dll.IsPalindrome(dll.Head)}");
}