Amazon Software Development Engineer - Intern interview questions

I applied for an internship at Amazon for last summer and they contacted me this past November to set up an interview in January. I believe they kept my application to be reconsidered once I was a junior in college. I had two 45-minute interviews on the phone, separated by a 15 minute break. During the first interview, the interviewer asked me first to talk a little about myself since he had not read my resume yet. He was very kind and understanding. He told me to write a program that reverses the words in a sentence string. I wrote it in Java and read him back the code when I had finished. While I was writing the code, he asked me to talk through my logic and explain what I was doing. He was more concerned with the algorithm than the actual semantics and he said it wasn't a problem if I forgot some of the names of the java functions on strings, etc. Often, when I noted something important for the problem, he'd say it "sounds reasonable" or "makes sense to me." He was very reassuring and it was nice to talk with him on the work we did. After I finished the code, he asked about what kinds of strings I might use to test this and he also asked me to consider how the program might be improved, e.g. how the program would handle a semi-colon. Also, he asked me to evaluate computational and memory complexity in terms of the number of characters in the string. At the end he asked if I had any questions, and I didn't really have any at that time. The second interview consisted of a couple more questions, and the interviewer was female. She asked me to go to a code sharing website so she could see the program I wrote. First, she had me write a program that compares if two binary trees are equal. I wrote it in Java. She was also very helpful, and helped me figure out an issue if I was a little stuck. Many of the methods I called were hypothetical, in a sense, using a previous java implementation of a binary tree I had implemented as a reference. After I completed that task, she asked me to explain the difference between an array and a linked list and when you might use either one. At the end, I asked her about the male:female ratio at Amazon and what her experience has been, being a female, as I attend a women's college.