Given nums + window size k, return the max for each sliding window in O(n) time complexity.

"The process was pretty rigorous, mainly because the bar at E6 felt more about scope and judgement than just solving the questions. Recruiter was clear and helpful. The coding rounds went ok, but I spent too long explaining some edge cases. Design was probably the strongest part, good back-and-forth and tradeoffs. Behavioral was fine, though I could’ve been more specific with impact numbers. Overall, a solid process but definitely tiring."