in first round - 1.design database table that can store comments like facebook. but there could be hierarchy of replies possible. design table to store them and query them in a way that each complete set of comments with their reply can be resulted. 2.Design ranking system, like in oyo room, there could be different ranking systems like user feedback and audit feedback etc. you should allow user to query all of them or few of them. the query should be generic enough. In second round- 1. calculate a to the power of n (interviewer was under impression that in order to do that u have to multiply a n times :D). optimize it to logn. 2. in an array every number present in pairs except one. find out one number which is not present in pair. (u can't sort or use extra space). (again this funny interviewer wanted to use bit-wise operator xOr to solve this which he was rigid. )
