Sliding Window Rate Limiter

Problem

Implement a class RateLimiter that enforces a per-client sliding-window rate limit. The constructor receives an integer limit and an integer window_size in seconds. Implement a method allow(client_id, timestamp) that returns True if the request should be accepted and False if it should be throttled. Requests are counted separately for each client_id, and only requests with timestamps in the inclusive range [timestamp - window_size + 1, timestamp] count toward the limit.

Constraints

• 1 <= limit <= 10^5
• 1 <= window_size <= 10^9
• timestamp values passed for a given client_id are non-decreasing
• client_id is a non-empty string