Amazon Software Development Engineer interview questions

applied online, received phone interviews twice

I Applied Online and got a call for onsite interview. There was some interview event going on and so I did not have to appear for Phone interview prior to this interview. I was flied to Seattle and had four rounds of interview. All the questions were focused on Algorithms and Data Structures. Questions were 1. "Solve a maze", you have a 2D matrix with 1's as blocked and 0's as path. Find a path from one corner to another, backtracking should be allowed. 2. Prove that tree is BST. 3. Ransom note problem - prepare a note(array) from a given magazine(array). 4. Keep track of history of users of Amazon site in pairs of 3 pages that they have consecutively visited.