Grandstream Networks Software Engineer interview questions

1. System Design of an elevator. 2. find missing number/ better way to solve it. 3. Multi-threads and dead lock. 4. write a function to determine a int is power of two. 5. write a function to determine a int is prime. 6. Given 7 numbers, each represent three character on the phone, write a function to print out all the possible combinations.

some basic design, algorithm and data structure.