When I interviewed at Microsoft the same thing happened. The final interviewer asked me a question I had already solved while studying. I told him I had alread

When I interviewed at Microsoft the same thing happened. The final interviewer asked me a question I had already solved while studying. I told him I had already seen the question before and knew the answer. He said that’s fine and just had me show him the solution. We used the extra time to just chat about my interests and side projects and I got the offer anyway. So it doesn’t matter, you didn’t “cheat” any more than I did.