I went through referral. The first round was written. I was supposed to answer 3 question. Then there are next 4 face to face techinical round where they observe your way to approach to solution. You need to know all good algorithm to solve question. Face to face round will be of 45 minutes to 1 hour. And you're expected to answer 3 question during that. Even if you know the question don't bang on. Solve from the brute force and then optimize it.