To add insult to the injury: he will probably not pass the Facebook coding interview. I tried (for a different position) and failed, due to a bullshit reason. It was a coding interview with two problems, 1-hour time limit, and an interviewer who watches how you enter code into their online editor without the possibility to run anything.
The problems were not that hard, the real difficulty was due to the time limit.
During my previous experience as a software developer I have acquired a habit to write an obviously-correct but non-optimized solution to every problem, to use as something to compare a better solution to, i.e. as a test factory. So, I had only enough time to solve the first problem correctly, and to implement a wasteful solution to the second one. In retrospect, implementing the "obviously correct" but wasteful solution would not have helped, because I could not compare the results anyway.
In my opinion, the test selects for people who are lucky enough to discover and implement the non-obvious optimization correctly from the first attempt. Or, as I have discovered later, who have bought all books on programming interview preparation, because the problems were actually non-unique.