Bloomberg Financial Software Engineer Intern interview questions

I took an online test which was pretty easy and then I took the phone interview. I had a friend who had taken the phone interview a few weeks before me and the questions they asked him were pretty easy. They asked me pretty basic questions in the beginning and then asked me a difficult question. They asked me, what is the best way to find the duplicates within two intersecting linked list. The answer I gave was very inefficient so they gave me hints but I was really nervous and I wasn't able to figure it out. I havent heard from them yet so I doubt I will get accepted for the in-house interview.