using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

​

public class Program

{

    private static Random _rand = new Random();

    public static List<string> ListofSimpleString(int scale)

    {

        return Enumerable.Range(0, scale).Select(x => Enumerable.Range(0, 10).Select(y => (char)_rand.Next(255)).ToString()).ToList();

    }

​

    public static List<string> ListofSimpleString2(int scale)

    {

        return Enumerable.Range(0, scale).Select(x => Enumerable.Range(0, 10).Select(y => (char)_rand.Next(48, 95)).ToString()).ToList();

    }

​

    public static List<string> ListofSimpleString3(int scale)

    {

        return Enumerable.Range(0, scale).Select(x => _rand.Next(1000).ToString()).ToList();

    }

​

    public static List<string> ListofSimpleString4(int scale)

    {

        return Enumerable.Range(0, scale).Select(x => _rand.Next(10000).ToString()).ToList();

    }

​

    public static List<string> ListofSimpleString5(int scale)

    {

        return Enumerable.Range(0, scale).Select(x => "duplicate value").ToList();

    }

​

    public static IEnumerable<string> GetDuplicatesDictionary(IEnumerable<string> original)

    {

        var dict = new Dictionary<string, bool>();

        bool isReturnedDupl;

        foreach (var s in original)

            if (dict.TryGetValue(s, out isReturnedDupl))

            {

                if (isReturnedDupl)

                    continue;

                dict[s] = true;

                yield return s;

            }

            else

                dict.Add(s, false);

    }

​

    public static IEnumerable<string> GetDuplicatesHashSet(IEnumerable<string> original)

    {

        var hs = new HashSet<string>();

        foreach (var item in original)

        {

            if (!hs.Add(item))

            {

                yield return item;

            }

        }

    }

​

    public static void Main()

    {

        long total = 0;

        var data = ListofSimpleString5(10000);

        for (int i = 0; i < 10; i++)

        {

            var sw = new Stopwatch();

            sw.Start();

            var result = GetDuplicatesHashSet(data).ToList();

            sw.Stop();

            total += sw.ElapsedMilliseconds;

        }

​

        Console.WriteLine("HashSet " + total / (decimal)10);

        total = 0;

        for (int i = 0; i < 10; i++)

        {

            var sw = new Stopwatch();

            sw.Start();

            var result = GetDuplicatesDictionary(data).ToList();

            sw.Stop();

            total += sw.ElapsedMilliseconds;

        }

​

        data = ListofSimpleString4(10000);

        Console.WriteLine("Dictionary " + total / (decimal)10);

        for (int i = 0; i < 10; i++)

        {

            var sw = new Stopwatch();

            sw.Start();

            var result = GetDuplicatesHashSet(data).ToList();

            sw.Stop();

            total += sw.ElapsedMilliseconds;

        }

​

        Console.WriteLine("HashSet " + total / (decimal)10);

        total = 0;

        for (int i = 0; i < 10; i++)

        {

            var sw = new Stopwatch();

            sw.Start();

            var result = GetDuplicatesDictionary(data).ToList();

            sw.Stop();

            total += sw.ElapsedMilliseconds;

        }

​

        Console.WriteLine("Dictionary " + total / (decimal)10);

    }

}