using System;

using System.Collections.Generic;

public class Program

{

    public static List<string> EmptyFile = new List<string>();

    public static List<string> OneLineFile = new List<string> {"1"};

    public static List<string> TwoLineFile = new List<string> {"1", "2"};

    public static List<string> BiggerFile = new List<string> {"1", "2", "3", "4"};

    public static void Main()

    {

        //empty file

        ProcessFile("anything", new List<string>());

        //one entry

        ProcessFile("notfound", new List<string> {"1"});

        ProcessFile("1", new List<string> {"1"});

        //two entiries

        ProcessFile("notfound", new List<string> {"1", "2"});

        ProcessFile("1", new List<string> {"1", "2"});

        ProcessFile("2", new List<string> {"1", "2"});

        //more than 2 entries

        ProcessFile("notfound", new List<string> {"1", "2", "3"});

        ProcessFile("1", new List<string> {"1", "2", "3"});

        ProcessFile("3", new List<string> {"1", "2", "3"});

        ProcessFile("2", new List<string> {"1", "2", "3"});     

    }

    public static void ProcessFile(string entry, List<string> file)

    {

        Console.WriteLine("------------------------------------");

        Console.WriteLine("entry: " + entry);

        Console.WriteLine("file:");

        foreach(var item in file)

            Console.WriteLine(item);

        Console.WriteLine(Environment.NewLine);

        int fileLength = file.Count;

        int linePointer = 0;

        int userLine = -1;

        //find user

        while(userLine < 0 && linePointer < fileLength)

        {

            if(file[linePointer] == entry)

            {

                userLine = linePointer;

            }

            linePointer++;

        }

        Console.WriteLine("user found: " + (userLine > -1).ToString());

        //only modify file if the user was found

        if(userLine > -1)

        {

            //traverse file until entry to remove

            linePointer = 0;

            while(linePointer < userLine)

            {

                linePointer++;

            }

            //remove line           

            file[linePointer] = "";         

            //backfill

            while(linePointer < fileLength - 1)

            {

                file[linePointer] = file[linePointer + 1];

                linePointer++;

            }

            //delete the last line

            file[fileLength - 1] = "";

        }

        Console.WriteLine("resulting file:");

        foreach(var item in file)

            Console.WriteLine(item);

        Console.WriteLine(Environment.NewLine);

        Console.WriteLine("------------------------------------");

        Console.WriteLine(Environment.NewLine);

    }

}