I think if you were to put this on leetcode, it'd likely rank as an Easy, maaaaaybe it would barely make it to Medium, no? Now, remember, it's not like I ask the question and then I sit back and quietly wait for the candidate to make the perfect solution by themselves. Interviewing is a back-n-forth chat. I'm always happy to guide people through the solution. It's all about how cooperative and supportive your intervieweer is!