Compute moving average over last N stream

You are given an integer N and an unbounded stream of integers arriving one by one. After each new integer arrives, output the average of the last N integers seen so far. Requirements: - If fewer than N integers have arrived, average over all integers seen so far. - The solution should support efficient updates per element. Follow-up: - How would you modify the design if more recent numbers should have higher weight (e.g., exponentially decaying weights or a custom weight vector over the last N items)?