Java + Count duplicates from int array without using any Collection or another intermediate Array

Question

As a part of the Java interview question paper I have got following issue to solve. But I am bit wonder whether how can I implement it without any Collection or intermediate

Answer 1

This is the simplest solution I can think of. I just added an extra counter so that integers with two or more repetitions still in the array are ignored.

static int findNumber(int[] arr) 
{  
    int duplicateCounter = 0;

    System.out.print("Duplicates: ");

    for(int i = 0; i < arr.length; i++)
    {
        boolean duplicate = false;
        int numOfOccurrences = 1;

        for (int j = (i+1); j < arr.length; j++)
        {
            if (arr[i] == arr[j])
            {
                numOfOccurrences++;
                duplicate = true;
            }
        }
        if(numOfOccurrences == 2 && duplicate == true)
        {
            duplicateCounter++;
            System.out.print(arr[i] + " ");
        }
    }

    return duplicateCounter;
}

My test run: Test run

Input: 1, 2, 3, 4, 2, 4, 1, 1, 1

Duplicates: 2 4 1

Number of duplicates: 3