agregate.cs

static int Proc(int[] A)
        {
            if (A.Length < 3)
            {
                return A.Length;
            }
            var seed = new Tuple<int, int, int, int>(A[0], A[1], 2, 2);
            return A.Aggregate(seed,
                (a, b) =>
                {
                    var x = a.Item1;
                    var y = a.Item2;
                    var curr = a.Item3;
                    var max = a.Item4;
                    if (x == y && b == y && b == x)
                    {
                        curr = 1;
                        max = Math.Max(curr, max);
                        return new Tuple<int, int, int, int>(x, y, 1, max);
                    }
                    else if (b != x && b != y)
                    {
                        curr = 2;
                        x = y;
                        y = b;
                        max = Math.Max(curr, max);
                        return new Tuple<int, int, int, int>(x, y, 2, max);
                    }
                    else
                    {
                        curr++;
                        max = Math.Max(curr, max);
                        return new Tuple<int, int, int, int>(x, y, curr, max);
                    }
                },
                (a) =>
                {
                    return a.Item4;
                });
        }