Question

Please write in C#

Write a method in C# int[]GetDuplicatesIndices(int[]array), which takes an array of integers and returns an array that holds the indices of all the duplicates.

Example if the array has the following value 10, 5, 3, 7, 5, 11, 15, 13, 11, 6, 3, 19 then note that the value 5 has duplicate at index 4, value 3 has a duplicate at index 11, and value 7 has a duplicate at index 6. So the method should return an array containing 4, 11, 6.

Answer 1

using System;

public class DuplicatesIndices
{
    public static int[] GetDuplicatesIndices(int[] array)
    {
        int count = 0;
        for (int i = 0; i < array.Length; i++)
        {
            for (int j = 0; j < i; j++)
            {
                if (array[i]==array[j])
                {
                    count++;
                    break;
                }
            }
        }
        
        int[] indices = new int[count];
        int index = 0;
        for (int i = 0; i < array.Length; i++)
        {
            for (int j = 0; j < i; j++)
            {
                if (array[i]==array[j])
                {
                    indices[index++] = i;
                    break;
                }
            }
        }

        return indices;
    }
    
    public static void Main(string[] args)
    {
        int[] arr = {10, 5, 3, 7, 5, 11, 15, 13, 11, 6, 3, 19};
        int[] indices = GetDuplicatesIndices(arr);
        for (int i = 0; i < indices.Length; i++)
        {
            Console.Write(indices[i] + " ");
        }

        Console.WriteLine();
    }
}