Thumbtack Software Engineer New Grad interview questions

It is supposed to be coding challenge, phone interview, on-site interview. I only made it to phone interview stage, then they decided not to continue the process. I think I was just nervous for the interview.

I applied online. About a week later they sent me a link to their coding challenge. I finished the basic implementation in about 80 minutes (the upper end of what they said it should take), but then proceeded to spend many hours implementing a self-balancing binary tree structure because technically the built in structure wouldn't perform well enough, which was frustrating and I suspect a flaw in their wording rather than an actual requirement (or perhaps just a flaw in the language I chose that the structure wasn't already there). A few days after submitting it, they got back to me asking to schedule a phone interview. It was a pretty typical phone interview. I liked the guy giving it to me though. He responded well to the questions I had about the company, and I was impressed that part of his coding question involved writing tests. They got back to me the same day saying I was moving forward with the onsite interview (perhaps because I had emailed them to say I was going to be in the San Francisco area for other interviews the following week). I had a full onsite (4 technical interviews, 1 culture fit interview with a co-founder) on a Thursday. It went fairly well, nothing too difficult. The lunch was kind of awkward though since we only had 30 minutes to eat, and the guy I was eating with was also trying to talk to me while we ate. At the end of the day, a recruiter told me that I could expect to hear back from them Friday (the next day) or Monday, which blew me away since every other place I had thus far interviewed at had had at least a week to get back to me for every step. I actually wound up hearing back from them before I heard back from the companies I had interviewed earlier that week. The wound up getting back to me on the Monday (1-2 business days after), saying they wanted to extend me an offer. The offer itself was pretty nice; right off the bat it was more than I had hoped for salary-wise (although admittedly, I wasn't sure where to set my expectations since it was my first job and in an area with a higher cost of living than I was used to). I was told they liked to make "strong offers" right out the door without needing to bargain. For all I know, that may have been a line, but given that it was already higher than I had been hoping for, I decided to just roll with it.