using System.Collections.Generic;
namespace ConsoleApp10
{
    public static class RemoveDuplicates
    {
        public static void Remove(int[] array)
        {
            var hashSet = new HashSet<int>();
            var j = 0;
            for (var i = 0; i < array.Length; i++)
            {
                if (!hashSet.Contains(array[i]))
                {
                    hashSet.Add(array[i]);
                    array[j++] = array[i];
                }
            }
            //set -1 for removed duplicates
            while (j < array.Length)
            {
                array[j++] = -1;
            }
        }
    }
}