public void MissingNumberTest_1()
        {
            var solution = new _0268_MissingNumber();
            var result   = solution.MissingNumber(new int[] { 3, 0, 1 });

            Assert.AreEqual(2, result);
        }
        public void MissingNumberTest_3()
        {
            var solution = new _0268_MissingNumber();
            var result   = solution.MissingNumber(new int[] { 9, 6, 4, 2, 3, 5, 7, 0, 1 });

            Assert.AreEqual(8, result);
        }