67. Design Hit Counter

Design a time-based hit counter tracking system.

Requirements

Implement

class HitCounter {
  hit(timestamp) {}
  getHits(timestamp) {}
}

• hit(timestamp): Record a request event that occurred at the specified timestamp.
• getHits(timestamp): Return the total hits recorded within the past 300 seconds.
• The sliding window must consider bounds exactly 300 seconds long (specifically (timestamp - 300, timestamp]).

Edge Cases

• Timestamps are guaranteed to be monotonic (delivered in chronological order).
• Multiple hits can arrive at the exact same timestamp. Ensure your storage mechanism accurately supports concurrent counts.

Example Usage

const counter = new HitCounter();
counter.hit(1);       // hit at timestamp 1
counter.hit(2);       // hit at timestamp 2
counter.hit(3);       // hit at timestamp 3
counter.getHits(4);   // get hits at timestamp 4, return 3
counter.hit(300);     // hit at timestamp 300
counter.getHits(300); // get hits at timestamp 300, return 4
counter.getHits(301); // get hits at timestamp 301, return 3