Amazon Software Development Engineer interview questions

I passed online assessment first, then was invited to onsite interview. We had pizza with the interviewers and asked some questions about Amazon. Four rounds onsite interview, the last round was bar raiser, one Chinese interviewer didn't give any hint, others were kind. Some design questions were asked. The questions were interesting and you can discuss it with the interviewers.

Referred by a friend and got one round of phone and then onsite. Phone interview questions are pretty easy: 1. best time to buy and sell stock; 2, design a locker room for a mall. Five rounds of onsite: (1), 1. when you disagree with your manager? 2. Big decision you made in last three months? 3, What did you do when you did something wrong? 4, biggest challenge in your past? 5, how do you solve conflicts? (2), generate a random number which has length of n and are unique for each digit. input: n=4, output: 1342 follow up: optimize and if we have a shuffle function (3), 1. valid a parentheses ‘()’ 2. valid a palindrome 3. design a validator which validate many aspects (4), Design a game User, character, Weapon, bag, Direction, (move up, down, left, right) (5), 1. valid a node which has the same value as its decedents if any 2. flat a linked list