Solution: Find Duplicates in an Array with No Repetition

using System;
class Program
{
    /// <summary>
    /// Method to find duplicates in a given array.
    /// </summary>
    /// <param name="arr">An array of integers.</param>
    /// <returns>An array of duplicate integers with no repetition.</returns>
    public static int[] FindDuplicates(int[] arr)
    {
        int[] result = new int[arr.Length];  // An array to store duplicates
        int resultIndex = 0;
        for (int i = 0; i < arr.Length; i++)
        {
            for (int j = i + 1; j < arr.Length; j++) // Starting from i + 1
            {
                if (arr[i] == arr[j])
                {
                    bool alreadyExists = false;
                    for (int k = 0; k < resultIndex; k++)
                    {
                        if (result[k] == arr[i])
                        {
                            alreadyExists = true;
                            break;
                        }
                    }
                    if (!alreadyExists)
                    {
                        result[resultIndex] = arr[i];
                        resultIndex++;
                    }
                }
            }
        }
        int[] finalResult = new int[resultIndex];
        Array.Copy(result, finalResult, resultIndex);  // Copy to a new array with correct size
        return finalResult;
    }
    // Driver to test above code
    static void Main()
    {
        int[] arr = { 1, 2, 5, 1, 4, 2, 1, 1 };
        int[] result = FindDuplicates(arr);
        Console.WriteLine("[" + string.Join(", ", result) + "]");
    }
}