using System;

using System.Collections.Generic;

using System.Collections;

using System.Linq;

public class Program

    {

       public static void Main(string[] args)

        {

            List<List<string>> dutchOutput = new List<List<string>>();

           List<string> row = new List<string>();

           row.Add("1");

           row.Add("empty");

           row.Add("2");

           row.Add("empty");

           row.Add("3");

           row.Add("call");

           row.Add("4");

           row.Add("call");

           row.Add("5");

           row.Add("call");

           row.Add("6");

           row.Add("put");

           row.Add("7");

           row.Add("put");

           dutchOutput.Add(row);

           List<List<string>> finalOutput = new List<List<string>>();

           List<List<string>> skippedRows = new List<List<string>>();

           string currentCallPutValue = "";

           string lastCallPutValue = "";

           bool addAlternateRow = false;

           bool checkSkippedRows = false;

           foreach(var item in dutchOutput){

               currentCallPutValue = item[1]; //call or put

               if(currentCallPutValue == ""){

                    finalOutput.Add(item);   

               }

               else{

                   if(string.IsNullOrEmpty(lastCallPutValue))

                   {

                       finalOutput.Add(item);  

                   }

                   else if(!string.IsNullOrEmpty(currentCallPutValue) && !string.IsNullOrEmpty(lastCallPutValue) && currentCallPutValue == lastCallPutValue)

                   {

                       if(addAlternateRow && currentCallPutValue == "put")

                       {

                          var selectedRow = skippedRows.Where(f=>f[1] == "call").FirstOrDefault();

                           finalOutput.Add(selectedRow);

                           skippedRows.Remove(selectedRow);

                       }

                       skippedRows.Add(item);

                   }

                   else if(!string.IsNullOrEmpty(currentCallPutValue) && !string.IsNullOrEmpty(lastCallPutValue) && currentCallPutValue != lastCallPutValue)

                   {

                       addAlternateRow = true;

                       finalOutput.Add(item);  

                   }

               }

               lastCallPutValue = item[1];

           }

        }

    }

​