I had a coding challenge and two rounds of phone interviews. The coding challenge wasn't hard, it was similar to a permutation problem, you can solve it using depth first search, but be sure to optimize your code. The first round of coding interview was a tree problem. If you know your tree traversal you're set. The second round was an array questions. I solved all the questions in the interview but was still rejected. They didn't get back to me about the rejection until 2 weeks later.