Amazon Software Development Engineer, interview questions

The interviews consisted of 2 technical phone interviews. I was contacted first by a recruiter who called me to set up a phone screen because I missed his emails. Everybody seemed to know their stuff and were fairly nice. Both phone screens were similar in that they asked general questions about my experience based on my resume and then dived into OOP design questions and one or two algorithm questions. I was asked this question in the first interview: Given an immutable singly linked list of some object with pointer to next element, find the nth element from the end of the linked list.