Welcome to your interview.
The question is on your right: Memory-Efficient Set Operations. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
Given two arrays containing numbers between 1 and 127, how would you find the union and intersection of these arrays while consuming the absolute minimum amount of memory?