I passed a HackerRank phone screen and received an offer for an on-site interview.

As other reviewers have mentioned, the on-site interview process is very disorganized. I didn't even get an email about the schedule for the day.

This might, in fact, be intentional, since your interviewer escorts you out early after the first two technical interviews if you don't pass. I never even got a chance to speak to anyone in HR during the entire day.

Sure, you might make your interview process slightly more efficient by doing this, but at the cost of alienating those whom you've judged through only two imperfect interviews. It makes you think about how they treat their employees here.

Reverse a string.

Find islands in a grid.

Design a data structure that stores counts of words in a text file, as well as counts for every line.