One HR interview, introducing the basic interview process. You just need to answer some simple questions about your resume. After that, they will send you an email describing all the things you need to master before the tech interview, including the site, type of questions, and so on.

Two Tech interview. Solve algorithm problems:

1. Traverse a binary search tree and find the sum of the tree.
2. Return all subsets of size k whose sum is n.

Be sure to use Topcoder; it's a wonderful site with great tutorials. Even better, it provides a practice room where you can test your code and observe its performance.

However, my suggestion is that you start with Google Docs, because that's how you will really use it in an interview. Only after you have finished coding in your Google Doc should you copy and paste your answer into your Topcoder practice room system to test it. You should also do this within a time limit, which is not 45 minutes, because the real interview will leave some time for questions and initial chat.

Therefore, it would be appropriate if you could solve the problem within 30 minutes. The problem will not be too hard, but it definitely requires strong preparation.

second question, because that requires a lot of performance consideration.