Google Software Engineer - L3 interview questions

3 rounds: 1st - Online Assessment, 2nd, online - 2 interviews (1 behavioral and 1 dsa), 3rd onsite - 2 interviews (both dsa). i was expected to go from brute force to optimal soln and explain tradeoffs, edge cases and time-space complexity

Technical round 1, was asked a simple array question, then how to optimise it, code in python, what is a generator, how to use yield to flatten the iterator of an array. Follow up was a deep nested array, how to flatten it, I use DFS, then interviewer ask how to use yield, and generator to solve this question