Amazon Software Development Engineer interview questions

I applied through their career portal and recieved their mail for online assessment. The first round was easy: 7 code debugging questions, and 35 questions based on Reasoning skills. I cleared it. The 2nd assessment was a week later. In 70 mins, I was asked to solve two coding questions. I could not understand the return type they used in the function and hence coudn't solve it. Two days later, I got my rejection mail.

Initially we had an online coding test from which 34 members were shortlisted including me and the interview had 4 F2F technical rounds (there was no HR round separately) and in each round their main focus was on Data Structures and Algorithms. First and Second rounds consisted of questions on already existing DSA and 3rd and 4th rounds consisted of questions on designing a optimal data structure which would satisfy the requirements they give.