# Minimum Cars for Rental Requests You receive rental requests, each with a unique request identifier, pickup time, and return time. Every request must be served. One car may serve multiple requests whose time intervals do not overlap, and a car returned at time t may be picked up by another request at the same time. Return both a deterministic request-to-car assignment and the minimum number of cars used. ## Function Contract Implement `assign_cars(request_ids, pickup_times, return_times) -> list[list[int]]`, where corresponding indices describe one request. Car identifiers start at 0. Process requests in ascending `(pickup_time, return_time, request_id)` order. Whenever multiple previously used cars are available, choose the smallest car identifier; when none is available, allocate the next consecutive identifier. Return `[[minimum_car_count], [request_id, car_id], ...]`, with assignment rows sorted by request identifier. ## Constraints - 0 <= number of requests <= 200000. - Pickup and return times are integers between 0 and 10^9. - For every request, pickup time is strictly less than return time. - All three input arrays have equal length, and request identifiers are unique integers between 0 and 10^9. ## Examples ```text request_ids = [20, 10, 30], pickup_times = [1, 2, 5], return_times = [5, 4, 7] output = [[2], [10, 1], [20, 0], [30, 0]] ``` ```text request_ids = [8, 4], pickup_times = [1, 3], return_times = [3, 5] output = [[1], [4, 0], [8, 0]] ``` ```hint Test simultaneous boundaries Include a request whose pickup equals another request's return, plus several requests that begin together. ``` ```hint Check reproducibility The same request set in a different input order must produce the same assignment under the stated tie rules. ```