Design Hit Counter

Design a hit counter which counts the number of hits received in the past 5 minutes (that is, the past 300 seconds). Implement the HitCounter class:

• HitCounter() Initializes the object of the hit counter system.
• void hit(int timestamp) Records a hit that happened at timestamp (in seconds). Several hits may happen at the same timestamp.
• int getHits(int timestamp) Returns the number of hits in the past 5 minutes from timestamp. You may assume that calls are made in chronological order, so timestamp is monotonically increasing.

HitCounter hitCounter = new HitCounter(); hitCounter.hit(1); hitCounter.hit(2); hitCounter.hit(3); hitCounter.getHits(4); // return 3 hitCounter.hit(300); hitCounter.getHits(300); // return 4 hitCounter.getHits(301); // return 3

Multiple hits in the same second share the same bucket, but all of them still count within the 300-second window.