Amazon Software Development Engineer interview questions

After two phone interview both lasting approximately 45 minutes, I was invited for an on-site interview at Amazon's Seattle office. Airfare and Hotel were prepaid. Other incidental expenses will be refunded after receipts are submitted. There were total of six interviews including one with HR Personnel and one with hiring manager. Remaining four interviews were purely technical with some behavioral components to them. Interview with hiring manger was purely behavioral and the one with HR personnel was purely regarding immigration, work-permit and benefits. I thought the interviews went well, but it seems they were not satisfied. Overall I think the interview process was fair.

2 phone interviews: 1st interviewer 1. given an array of integers how would you search an element?...I said binary search. He asked what is it and time complexity. 2. He extended the above ques to n x n matrix where rows are sorted and columns are not. How will you search an element. He dint ask me to code.Just tell the algo and complexity 3. Built further on the abv ques. Now both rows and columns are sorted. 4. Abt my web apps project...abt HTTP request, servlets etc 5. Model a deck of cards(this is v common ques...u will find in glass door) 6. one thing you want to change abt amazon 7. abt dns server 2nd interviewer 1. tell about a project you are working on this sem. What technologies? 2. wht data stuc u knw? 3.write a function isSubtree(tree t1, tree t2) to check if one tree is sub tree of other. 4. write a func that takes in array and an int k and find all pairs that sum up to k