public void DuplicatesWithRecursion_ThreeSetsChar()
        {
            DuplicatesWithRecursion recursion = new DuplicatesWithRecursion();
            string res = recursion.Dedup("mississipie");

            Assert.Equal("mpie", res);
        }
        public void DuplicatesWithRecursion_ThreeCharDups()
        {
            DuplicatesWithRecursion recursion = new DuplicatesWithRecursion();
            string res = recursion.Dedup("mxxxy");

            Assert.Equal("my", res);
        }
        public void DuplicatesWithRecursion_OneChar()
        {
            DuplicatesWithRecursion recursion = new DuplicatesWithRecursion();
            string res = recursion.Dedup("m");

            Assert.Equal("m", res);
        }
        public void DuplicatesWithRecursion_OnlyDups()
        {
            DuplicatesWithRecursion recursion = new DuplicatesWithRecursion();
            string res = recursion.Dedup("ississippi");

            Assert.Equal("", res);
        }