public void NumDistinctTest()
        {
            var solution = new _115_DistinctSubsequences();
            var result   = solution.NumDistinct("rabbbit", "rabbit");

            Assert.AreEqual(3, result);
        }
        public void NumDistinctTest_SEmptyString()
        {
            var solution = new _115_DistinctSubsequences();
            var result   = solution.NumDistinct("", "abc");

            Assert.AreEqual(0, result);
        }
        public void NumDistinctTest_NoMatch_2()
        {
            var solution = new _115_DistinctSubsequences();
            var result   = solution.NumDistinct("abcd", "de");

            Assert.AreEqual(0, result);
        }
        public void NumDistinctTest_2()
        {
            var solution = new _115_DistinctSubsequences();
            var result   = solution.NumDistinct("babgbag", "bag");

            Assert.AreEqual(5, result);
        }