I just got the OA online test, and it seems from their team not for the specific HR. The difficulty of OA testing is very high, with three questions in 90 minutes, which has already covered most of the difficult questions in LeetCode. For example, String Transformation has a very large amount of code, and it is basically difficult to complete these questions in an hour and a half, unless you have prepared some OA questions shared by others a long time ago in advance, or you are already a skilled LeetCode answering expert. Even if I finished all the questions, there would be no follow-up. It can be said that unfortunately I am.