02. Friendlist Maintenance

using System;
using System.Collections.Generic;
using System.Linq;

namespace _02._Friendlist_Maintenance
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> list = Console.ReadLine().Split(", ").ToList();

            List<string> list1 = new List<string>();
            List<string> command = new List<string>();
            command.Add("");
            int numBL = 0;
            int numLost = 0;
            bool flag = true;

            while (command[0] != "Report")
            {
                command = Console.ReadLine()
                    .Split()
                    .ToList();
                if(command[0] == "Report")
                {
                    break;
                }

                switch (command[0])
                {
                    case "Blacklist":
                        list1 = list;
                        list = Blacklist(list, command[1]);
                        flag = list1.SequenceEqual(list); // Има ли промяна в листа
                        if (!flag)
                        {
                            numBL++; // ако има промяна, увеличавам брояча
                        }
                        break;
                    case "Error":
                        list1 = list;
                        list = Error(list, command[1]);
                        flag = list1.SequenceEqual(list); // Има ли промяна в листа
                        if (!flag)
                        {
                            numLost++;  // ако има промяна, увеличавам брояча
                        }
                        break;
                    case "Change":
                        list = Change(list, command[1], command[2]);
                        break;
                }
            }
            Console.WriteLine($"Blacklisted names: {numBL}");
            Console.WriteLine($"Lost names: {numLost}");
            Console.WriteLine(string.Join(" ",list));
        }

        private static List<string> Change(List<string> arr, string v1, string name)
        {
            int index = int.Parse(v1);

            if (index >= 0 && index < arr.Count)
            {
                Console.WriteLine($"{arr[index]} changed his username to {name}.");
                arr[index] = name;
            }
            return arr;
        }

        private static List<string> Error(List<string> arr, string v)
        {
            int index = int.Parse(v);
            List<string> arrNew = new List<string>();

            for (int i = 0; i < arr.Count; i++)
                {
                    arrNew.Add(arr[i]);
                }

            if (index >= 0 && index < arr.Count)
            {
                if (arr[index] != "Blacklisted" && arr[index] != "Lost")
                {
                    Console.WriteLine($"{arr[index]} was lost due to an error.");
                    arrNew[index] = "Lost";
                }
            }
            return arrNew;
        }

        private static List<string> Blacklist(List<string> arr, string name)
        {
            List<string> arrNew = new List<string>();

            for (int i = 0; i < arr.Count; i++)
            {
                arrNew.Add(arr[i]);
            }

            if (arr.Contains(name))
            {
                int index = arr.IndexOf(name);
                Console.WriteLine($"{name} was blacklisted.");
                arrNew[index] = "Blacklisted";
            }
            else
            {
                Console.WriteLine($"{name} was not found.");
            }
            return arrNew;
        }
    }
}