Snap interview questions

I had only 1 video interview, but I didn't sign any NDA, so I can post all details and this review might actually be useful. In general, nothing interesting. They asked some unrelated questions about what I worked on and when one solution could be better than another. After wasting 30 minutes, I had only 30 minutes to solve the problem (I posted it below). They also expect that a candidate should have time to post the code on hackerrank and compile/run it there. Of course I didn't solve it in time, I agreed that the interveiw was failed and finished it. But I was still curious what the solution was, after 2 hours I finally wrote a working code. I will post my solution below.