Five Interviews:

• Talked about a past project and deep-dived into my thinking about it.
• Designed a probabilistic English language word tokenizer.
• Designed a data processing infrastructure for petabytes of data and estimated the cost & performance characteristics of the system.
• Permutated ways to count up to a number using a set of potential constituents.
• Explained how to efficiently choose numbers from a set and proved that the solution is the Big-O optimal solution.

I was asked to mathematically prove the Big-O bounds of an algorithm. I was a little rusty with my math, but my interviewer helped me, and I got it.