using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Globalization;

using System.Collections;

​

public class Program

{

    public static void Main(string[] args)

    {       

        var list = new List<string> { "[", "1", "2", "3", "]", "[", "2", "2", "]", "[", "3", "]" };

        int index=0;

        list.Select(item=> new { item=item, index= item=="]"? ++index : index })

                          .Where(c => !(c.item == "[" || c.item =="]"))

                          .GroupBy(g=>g.index)

                          .Select(e=> e.Select(c=>c.item)).Dump();

    }

}

​