В таком коде:

private static int[] Split(List<int> list)
        {
            const int splitter = 0;
            const int startstop = 9;

            var result = new List<int>();
            var start = true;

            for (var pos = 0; pos < list.Count; pos++)
            {
                if (start)
                {
                    if (list[pos] == startstop)
                    {
                        start = false;
                    }

                    continue;
                }

                start = true;

                var k = 0;
                var index = list.FindIndex(pos, i => i == startstop);

                if (index + 1 < list.Count)
                {
                    if (list[index + 1] != splitter)
                    {
                        start = false;

                        continue;
                    }
                    else
                    {
                        k = 2;
                    }
                }

                result.Add(index + k);
            }

            return result.ToArray();
        }

Предлагает убрать else:



ReSharper 2022.2.2
Microsoft Visual Studio Professional 2022 (64-bit)
Version 17.3.3