Flipkart rounds often ask medium-to-hard data structure problems where the follow-up pushes past the first answer. Sliding-window maximum is typical: a heap works, but the interviewer then asks for O(n). Reach for a monotonic deque when you need the maximum or minimum of every window as it slides. If the window is not fixed in size or you need any order statistic other than the max or min, a deque alone is not enough.