Find if a number is a power of 2 in constant time. reverse a linked list. Sort a linked list.

Couple of design questions were asked : 1. Design a lift 2. Design a music player with given number of states like pay , pause, stop, rewind. The player has to transition between the states and work as desired. Basically they wanted to see if you are aware of state design pattern and if you can implement the same. 3. Singleton pattern and questions around thread safety.

Some basic kernel concepts: 1. Multithreading, mutex, semaphore. 2. thread vs process. When to prefer which one. 3. Address space, memory management. 4. Design a program having 2 threads which reads from a given input array containing integers, One thread prints odd number and other thread prints even number. In one pass over the array, the prog should print whether the number is odd or even using these threads.