Finding duplicate elements in an array without using nested loops

[Dev Choudhary]

I recently had an interview which consisted of following problem. Please help with possible solutions.

Write a function in Java to find duplicate elements in an integer array without using nested loops ( for/ while / do while, etc ) and without using library functions.

[Liutauras Vilda]

Hi,

First of all, in Java there are no functions. More correctly would be to ask to write a program or method.

I'd say you could solve that with recursion if there's no restriction to use it.

[Campbell Ritchie]

Would a Stream be permissible?

Remember in an interview it is not what you say so much as how you say it. The way you approach the question and the sort of questions you ask for clarification count as much as the actual solution you produce. Whether saying the producing such code in real life merits instant dismissal is a good idea, I am not sure.

[fred rosenberger]

it says no NESTED loops, right?

use a loop, and use each element as a key to map. for each one, first check to see if the key exists - if so, you have a duplicate. if not, insert it.

[Piet Souris]

If two sets are used, and looking at the return type when you insert
an element into a set, the solution can be very short. As Fred says,
you need just one loop.

Worrying though, is this requirement:

Dev Choudhary wrote:(...) and without using library functions.

Whatever that means...

Greetz,
Piet