Computing the max of each size-k window the obvious way costs O(n*k). The move that cuts it to O(n) is a monotonic deque of indices, and why it stays linear catches most candidates off guard.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Computing the max of each size-k window the obvious way costs O(n*k). The move that cuts it to O(n) is a monotonic deque of indices, and why it stays linear catches most candidates off guard.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
