/// <summary>
/// This method removes duplicate from integer array
/// </summary>
/// <param name="a">input array</param>
/// <returns>integer array with no duplicate</returns>
public int[] RemoveUsingHash(int[] a)
{
	Hashtable ht = new Hashtable();
	for (int i = 0; i < a.Length; i++)
	{
		if (!ht.ContainsKey(a[i]))
		{
			ht.Add(a[i], a[i]);
		}
	}
	int[] output = new int[ht.Count];
	int j = 0;
	foreach (int item in ht.Keys)
	{
		output[j++] = item;
	}
	return output;
}

/// <summary>
/// This method uses array (bucket) of integer
/// </summary>
/// <param name="a">input integer array</param>
/// <returns>array of integers without duplicate content on it.</returns>
public int[] BucketRemove(int[] a)
{
	int[] bucket = new int[256];
	int count = 0;
	for (int i = 0; i < a.Length; i++)
	{
		if (bucket[a[i]] != 1)
		{
			bucket[a[i]] = 1;
			count++;
		}
	}
	int[] output = new int[count];
	int j = 0;
	for (int i = 0; i < bucket.Length; i++)
	{
		if (bucket[i] == 1)
		{
			output[j++] = i;
		}
	}
	return output;
}

/// <summary>
/// Removes duplicate in sorted array
/// </summary>
/// <param name="a">array of integers</param>
/// <returns>array of integers with no duplicate content (duplicate content moved to last part of array.)</returns>
public int[] RemoveDuplicate(int[] a)
{
	int j = 0;
	for (int i = 1; i < a.Length; i++)
	{
		if (a[j] != a[i])
		{
			a[++j] = a[i];
		}
	}
	return a;
}

int[] input = new int[] { 1, 2, 3, 4, 4, 5, 5, 6, 7 };
int[] a = BucketRemove(input);
foreach (int i in a)
{
	Console.Write(i + " ");
}
 
Console.WriteLine();
int[] b =RemoveUsingHash(input);
foreach (int i in a)
{
	Console.Write(i + " ");
}
 
Console.WriteLine();
int[] c = RemoveDuplicate(input);
foreach (int i in a)
{
	Console.Write(i + " ");
}

1 2 3 4 5 6 7
1 2 3 4 5 6 7
1 2 3 4 5 6 7