SAP Software Engineer interview questions

Received an email from SAP HR informing me I had been selected to attend a 2 hour on-site technical interview. The following week, I received another email asking me to attend the following day. On the day I met 2 Senior developers on the team and after a brief introduction, I was given some sample code to review (choice of javascript or java) and give my opinion on. We then proceeded to the whiteboard where I was asked to solve the minimum height of a binary search tree and write a function to find the unique character in a String.