I applied online and they scheduled a phone interview. Skype and an online editor were used for communication.

The interviewer was very focused on the code that I was writing. He asked detailed questions about every design decision I made, from choosing a data structure to structuring an if statement. The code wasn't long but it was complicated.

Can't say the tasks, but I will explain some key points.

There was only one question with two parts.

First part: A standard software engineering question where you implement a simple function using structures from the language library and argue why it is fast and easily maintainable.

Second part: The function from the first part is used in a more complex algorithm where you need to supply a couple of other functions. The focus is on speed, and you will probably need a custom data structure.