pattern recognition for data partition

using System;
using System.Collections.Generic;
using System.Text;
namespace ConsoleApplication612
{
    class Program
    {
        private class ValueSort : IComparer<int[]>
        {
            public int Compare(int[] x, int[] y)
            {
                if (x[1] > y[1])
                    return -1;
                else if (x[1] < y[1])
                    return 1;
                else
                    return 0;
            }
        }
        private class IndexSort : IComparer<int[]>
        {
            public int Compare(int[] x, int[] y)
            {
                if (x[0] > y[0])
                    return 1;
                else if (x[0] < y[0])
                    return -1;
                else
                    return 0;
            }
        }
        static void Main2(string[] args)
        {
            int[] data = new int[] { 1, 2, 1, 3, 2, 4, 5, 11, 10, 12, 10, 12, 13, 25, 21, 24, 20, 4, 5, 2, 3 };
            int[][] delta = new int[data.Length][];
            delta[0] = new int[2];
            delta[0][0] = 0;
            delta[0][1] = 0;
            for (int i = 0; i < data.Length - 1; i++)
            {
                delta[i + 1] = new int[2];
                delta[i + 1][0] = i + 1;
                delta[i + 1][1] = Math.Abs(data[i + 1] - data[i]);
            }
            Array.Sort(delta, new ValueSort());
            int groups = 4;
            int[][] topDelta = new int[groups - 1][];
            for (int i = 0; i < topDelta.Length; i++)
            {
                topDelta[i] = delta[i];
            }
            Array.Sort(topDelta, new IndexSort());
            List<List<int>> output = new List<List<int>>();
            int index = 0;
            for (int i = 0; i < topDelta.Length; i++)
            {
                List<int> group = new List<int>();
                for (int j = index; j < topDelta[i][0]; j++)
                {
                    group.Add(data[j]);
                }
                index = topDelta[i][0] + 1;
                output.Add(group);
            }
            List<int> group2 = new List<int>();
            for (int j = topDelta[topDelta.Length - 1][0]; j < data.Length; j++)
            {
                group2.Add(data[j]);
            }
            output.Add(group2);
            for (int i = 0; i < output.Count; i++)
            {
                Console.Write("Group" + i + ":");
                foreach (int value in output[i])
                {
                    Console.Write(value + ",");
                }
                Console.WriteLine();
            }
        }
    }
}