Amazon Software Developer Intern interview questions

I applied on internet. A few days after, they sent me a program to write. The program was not very difficult. But what they wanted was a program which could be very fast with a huge amounts of data. The program: I had a file representing a binary tree. In the file, it was coded like that: B,C NULL,B C,A ... Null meant that B was the main uppest node. Then, C was the son of B and A the son of C. The program took a depth and the file in input and should give the node which were at this depth in alphabetical order. After that, I received a notification to go in London. I was in front of two ingeneers of Amazon and it was technical questions. The question was not difficult but I misunderstood the question bacause of my english and so I lost a lot of time.

I have submitted my Resume online through their career website. Got a e-mail to schedule telephonic interview , within a week span.