Question

I was proud that I figured out the answer myself but then I read the question again and noticed the signature:

Write a method findDuplicates that will return an array consisting of all duplicate values that were found in a given array. For example, if given an array consisting of the values {1, 7, 3, 7, 3, 4, 1, 3, 2} the method would return an array consisting of the values {1,7,3}.

          public static int[] findDuplicates(int[] naVals)

What I have:

   public static int findDuplicates(int[] naVals)
   {
   Arrays.sort(naVals);
   for (int i = 1; i < naVals.length; i++)
   {
   if (naVals[i] == naVals[i-1])
   {
   return naVals[i];
   }
   }

   return -1;
   }
   }

and the test method:

@Test
   public void testQ7()
   {
       int[] naExpected1 = {1, 7, 3};
       int[] naTest1 = { 1, 7,3,7,9,4,1,3,7, 3,2};
      
       assertArrayEquals(naExpected1, Q7.findDuplicates(naTest1));
   }

Answer 1

public static int[] findDuplicates(int[] naVals)
{
    ArrayList<Integer> duplicates=new ArrayList<Integer>();
    for(int i=0;i<naVals.length;i++)
    {
      for(int j=i+1;j<naVals.length;j++)
      if(naVals[i]==naVals[j] && !(duplicates.contains(naVals[i]))) //element is not present in arraylist
      duplicates.add(naVals[i]); //add duplicate element
    }
    //convert ArrayList to array
    int[] a=new int[duplicates.size()];
    for(int i=0;i<duplicates.size();++i)
    a[i]=duplicates.get(i);
    return a;
}