Rate Limiter

Problem Implement a rate limiter: allow(clientId) returns true if the request is within the client's limit of N requests per time window W, false otherwise. Runnable code passing test cases is expected, not just discussion.

Input / Output

• Input: configured limit N and window W; calls allow(clientId) arriving at arbitrary timestamps.
• Output: boolean per call.

Constraints

• Many clients → per-client state must be compact; calls should be O(1) amortized.

Example

• N=3, W=60s: requests at t=0,10,20 → true; t=30 → false; t=61 → true (the t=0 request expired).