Design Sliding-Window Average Tracker

Design a class that tracks records in a sliding time window. Implement the following API: - `init(time_window)`: initialize the object with a window size. - `insert(record_id, value, timestamp)`: insert a new record. - `get_avg(timestamp)`: return the average `value` of all records whose timestamps fall within the most recent `time_window` ending at `timestamp`. Assumptions and requirements: - `record_id` is unique for each inserted record. - Timestamps are integers. - Calls to `insert(...)` and `get_avg(...)` are made with non-decreasing timestamps. - A record is considered active at time `t` if its timestamp is in the interval `[t - time_window + 1, t]`. - If no records are active in the window, return `0`. - The implementation should be optimized for the monotonic-timestamp constraint. Follow-up: - Support `update(record_id, new_timestamp)`, which changes the timestamp of an existing record while keeping its original value unchanged. - Explain how your design would change if inserts and queries could arrive with out-of-order timestamps.