using System;

using System.Linq;

using System.Collections.Generic;

​

public class Item

{

  public int Start { get; set;}

  public int Stop { get; set;}

}

​

public class Program

{

    public static void Main()

    {       

        var items = new Item[]{new Item{Start=1,Stop=2},new Item{Start=2,Stop=5},new Item{Start=8,Stop=10},new Item{Start=10,Stop=20}};

        var seq = GetContiguousSequences3(items);

        foreach(var seqItem in seq)

        {

            foreach(var item in seqItem)

            {

                Console.WriteLine(item.Start + " - " + item.Stop);

            }

            Console.WriteLine("--- end of group --");

        }

    }

    public static List<Item[]> GetContiguousSequences2(Item []items)

    {

        var currIdx = 1;

        return items.Select( (item,index) =>  new {

                item = item,

                index = index == 0 || items[index-1].Stop == item.Start ? currIdx : ++currIdx

            })

            .GroupBy(x => x.index, x => x.item)

            .Select(x => x.ToArray())

            .ToList();      

    }

    public static List<Item[]> GetContiguousSequences3(Item []items)

    {

        var res = items.Aggregate(new {Result = new List<Item[]>(), Curr = new List<Item>()}, (agg, item) => {

                if(!agg.Curr.Any() || agg.Curr.Last().Stop == item.Start) {

                    agg.Curr.Add(item);

                } else {

                    agg.Result.Add(agg.Curr.ToArray());

                    agg.Curr.Clear();   

                    agg.Curr.Add(item);

                }

            return agg;

        });     

        res.Result.Add(res.Curr.ToArray());

        return res.Result;

    }

    public static List<Item[]> GetContiguousSequences(Item []items)

    {

            var ret = new List<Item[]>();

​

            var i1 = 0;

            for(var i2=1;i2<items.Length;++i2)

            {

                //discontinuity

                if(items[i2-1].Stop != items[i2].Start)

                {

                    var num = i2 - i1;

                    ret.Add(items.Skip(i1).Take(num).ToArray());

                    i1 = i2;

                }

            }

            //end of array

            ret.Add(items.Skip(i1).Take(items.Length-i1).ToArray());

​

            return ret;

    }

}