Ask HN: Is Facebook interview is all random

Here is the text from one of the interviewer who clear the fb interview "The second interview was very hard they asked me a leetcode hard question and I was only able to solve it because I did the exact question before. Complete luck there. Personally I think it was unreasonable to expect someone to solve that difficult of a question in 30 minutes. The overall acceptance rate on the question on Leetcode is around 20%." https://leetcode.com/discuss/interview-question/563659/facebook-ml-engineer-santa-monica-pending