I approached an Nvidia representative during a campus career fair.

I was asked a couple of systems-related questions on the spot.

A few months later, I was contacted by a recruiter, and we set up a phone interview.

The interview had two rounds: the first one was pretty easy, while the second one was much harder.

I didn't get the job, but it was a really valuable experience, and the recruiter was really nice.

Given an array of numbers, in which all numbers except one occur twice (e.g., 1 2 3 2 3), find the unique number.