Google

I received an email from one of Google's recruiters offering me the possibility of entering the hiring process for a Software Engineer position. After a relatively simple phone interview, which included a programming problem (no code was necessary,

The interview process is hard to get in the first place and is even harder to pass once obtained. You can usually get an interview by receiving a referral; apart from that, it's difficult.

5 rounds: 1 behavioral and 4 technical. Overall, not very hard, but I could not get the optimal solution in the first technical round. I also spent too much time explaining my solution in the third technical round.