The whole process was pretty awful. The engineer didn't start with any introduction or resume, directly went into coding exercise. The screen question was not hard. It was "Leetcode.com" medium question. But I didn't know the optimal solution. I started with the brutal force solution. I asked the engineer if I need to implement it. He agreed to it. After that, I was working the optimization. He hinted me afterwards. I figured it out and coded it up. Then he asked me for optimization to NO extra space. I couldn't figure it out. And then he hinted condescendingly. But the algorithm requires constant space. I asked that the requirements are different from what you asked me before. And he said, "hmmm, but it's still better than yours". At that time, I knew that I fell the screening. I coded it up and then finished the interview off. I don't like the toxic comments from an interviewer. The interview was to show off how awesome the Facebook employees.