Amazon Sr. Technical Program Manager interview questions

Headhunted by in-house recruiter. Had brief conversation and then phone interview with hiring manager within a week. Then another phone interview within a week after that. Then came in for all day interviews with 8 people, 6 1:1 and 1 2:1. Was asked he usual background and project/program management questions. Was also asked when I last coded, what languages and so on. I had to design IT processes, database design etc. Was also asked to design an algorithm for finding the longest palindrome in a string of characters and how I would fix the US economy. People were generally nice but the process was grueling. Easily the hardest series of interviews in 20+ years in IT. Generally things seemed to go well but a few days later they called to say they weren't moving forward but I got no explanation at all as to why which was unsatisfying after the process.