Practicing on LeetCode

I have been reading the Computer Science Careers subreddit recently. There is a lot of talk about how to prepare for job interviews. Many people mention doing problems on LeetCode. I have never heard of that site. I want to interview for another job. Maybe I should be doing practice problems on there too.

So I created an account. Seems like I could proceed without paying for a developer subscription. I went to problem number one. The site was preconfigured to use C++ as the programming language. Does the site just use that because it is a popular language? Or did it figure out I know C++ from my profile?

Had some trouble getting my first entry to compile. The error messages were a bit cryptic. No trouble. I know how to debug, isolating the faults. Got my code to return the correct result for the sample inputs. Then I submitted my solution.

Was a bit disappointed that, although my solution was accepted, 95% of the other solutions executed faster than mine. Nobody told me we would be graded on speed. Next time I will have to optimize my solution.