public void StandardTests()
        {
            var input = new LinkedListNode<int>(1, 2, 3, 4, 5, 6);

            Assert.AreEqual(input.GetKthToLast(0).Value, 6);
            Assert.AreEqual(input.GetKthToLast(1).Value, 5);
            Assert.AreEqual(input.GetKthToLast(2).Value, 4);
            Assert.AreEqual(input.GetKthToLast(3).Value, 3);
            Assert.AreEqual(input.GetKthToLast(4).Value, 2);
            Assert.AreEqual(input.GetKthToLast(5).Value, 1);
        }
        public void LengthLessThanKTests()
        {
            var input = new LinkedListNode<int>(1, 2, 3, 4, 5, 6);

            Assert.IsNull(input.GetKthToLast(6));
        }