Elementum Senior Staff Software Engineer interview questions

In-person interview after the recruiter's call. 4 different engineers meet one after another. Couple of coding and couple of design questions. 1) Parse Tree: The interviewer seemed that he prepared the questions but the instructions were misleading. Explained the solution first by writing the solution in notepad. The interviewer mentioned that the solution works and asked me to code in the laptop. The coding was done in a laptop that is not setup with all the required tools. Ran out of time. He is the only one who showed full interest in finding out the actual skill set of the interviewee. 2) Merge sorted List: The engineer was not interested in discussing the solution, before coding. He wanted me to write code on the board. After writing code, started discussing. Looked like something else going on his mind. His thoughts were not organized, as I challenged him. Thought it is a 10min solution but took the whole time and walked out. I was sure that he didn't have any clue why he is intereviewing. 3) Design Shopping cart - random discussions. 4) Design Uber - Interviewer kept changing questions once you start answering. I ended up writing question on the board first before I started. He was interested in the data structure to locate the available drivers in the region/neighbourhood. I explained the geohash, hilbert curves, quadtree and the boundary box and also sited a white paper. But it appeared that he expected the word 'quadtree'.