Amazon Software Development Engineer interview questions

I had one of the worst experiences at Amazon among all the job interviews i have given so far. I was called for a f2f interview and after 6 technical rounds, they rejected me. I regretted not getting a offer. But after few days, i got a call from HR team again for the same positions. They asked me to interview again, citing it was for a different team. I was foolish to pursue this. I gave 7 technical interviews. This time, HR confirmed me that they would like to extend me the offer. I was happy. Many days passed but i did not receive any communication from them. Finally, after asking persistently, they said they are not extending this offer. And declined to give a reason why so. Pathetic experience ever !!