Meta Software Developer interview questions

Was contacted by an HR, she was very kind to talk to and provided enough material to prepare for the entire interview process starting with phone screen. Phone interview lasted EXACTLY 45 mins. Interviewer called me. Started with a brief intro about himself and then asked about my background. I took around 3 mins to give brief intro about my experience and I felt he was least interested in hearing i, I can say that b'coz I felt he was trying to stop me and jump to coding question. He didn't even comment anything about my experience, felt as if he is just following the protocol to get done with the interview. He asked me 1st question, I was able to solve it in 20 mins with optimal solution. Although no comment here from him whether as per him it is okay or not. Neither he asked me the run time complexity of the solution which was O(n). He then just jumped to another question. I took remaining of my time trying to get to the proper solution, but I think I was in the right direction b'coz I researched about that question after the interview. After couple of days I get a phone call from HR saying the feedback was not +ve. Interviewer felt my coding solutions were not optimal. I was shocked to hear this. Firstly, I solved 1 out of 2 questions properly and I didn't hear any feedback from hi while I solved the problem during the interview. If he thought it was not optimal, what made him jump to second question ?. He didn't even ask me complexity or at least he could have said "there can be much better solution can you think further ?". No feedback at all. As per the research I did and videos I saw, I guess FB interviewer tries to see your approach if it is not an optimal solution. In the end he was like "I only have time for 1 question to answer if you have any, or else I will be kicked out of this room". These were his words. I was like REALLY???. Company like Facebook doesn't have enough meeting/Interview rooms or do they reserve the room for exactly 45 mins when an interview is scheduled ?. I never felt comfortable during this interview, I felt I was rushed into it. I couldn't do much when I got the call from HR but I expressed my side of the story to the her.