using System;

using System.Collections.Generic;

public class Program

{

    public static int Main()

    {       

        int[] nums = new int[]{0,0,1,1,1,2,2,3,3,4};

        int length = 1;

        if (nums.Length == 1)

            return nums.Length;

        else

        {

            Do (nums[0]);       

            for (int i = 0; i < nums.Length; i++)

            {

                for (int j = 0; j < nums.Length; j++)

                {

                    if (list.Contains(nums[i]))

                        break;

                    else 

                    {                   

                        Do(nums[i]);

                        length++;

                    }

                }

            }

            Console.WriteLine(length);

            Mix(list, nums, length);

            foreach (var c in nums)

                Console.Write(c + " ");

            return length;

        }

    }

    static List<int> list = new List<int>();

    static void Do (int k)

    {

        list.Add(k);

    }

    static void Mix(List<int> list, int[] nums, int length)

    {

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

        {

            nums[i] = list[i];

        }

    }

}

​

​