using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Linq;

​

​

​

public class Program

{

    public static void Main()

    {

        var r = new Random((int)DateTime.Now.Ticks);

            const int size = 100;

            var arr = new int[size];

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

                arr[i] = r.Next(2);

         const int n = 100;

            var t = Stopwatch.StartNew();

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

                theFirstMethod(arr);

            t.Stop();

            Console.WriteLine("Elapsed: {0}ms", t.Elapsed.TotalMilliseconds);

​

            t = Stopwatch.StartNew();

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

                theSecondMethod(arr);

            t.Stop();

            Console.WriteLine("Elapsed: {0}ms", t.Elapsed.TotalMilliseconds);

​

            t = Stopwatch.StartNew();

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

                theThirdMethod(arr);

            t.Stop();

            Console.WriteLine("Elapsed: {0}ms", t.Elapsed.TotalMilliseconds);

    }

    static int[] theSecondMethod(int[] arr)

        {

            return new HashSet<int>(arr).ToArray();

        }

​

        static int[] theThirdMethod(int[] arr)

        {

            return arr.Distinct().ToArray();

        }

​

        static int[] theFirstMethod(int[] arr)

        {

            var length = arr.Length;

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

            {

                for (int j = i + 1; j < length;)

                {

                    if (arr[i] == arr[j])

                    {

                        for (int k = j; k < length - 1; k++)

                        {

                            arr[k] = arr[k + 1];

                        }

                        length--;

​

                    }

                    else

                        j++;

                }

            }

​

            int[] res = new int[length];

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

            {

                res[i] = arr[i];

            }

            return res;

        }

}

​

​