I applied for the job (and a couple others) on their website. A recruiter emailed me about this one within a few hours. We did a short phone screen, then set up a technical phone interview.

They called me a few days later. We used a link to Collab Edit so they could see what I was typing. I was asked a question. After I solved it, they wanted an optimized solution.

Given a set of numbers, determine if there exists a pair whose sum is 0.