public class HitCounter2 {

private int[] times;

private int[] hits;

public HitCounter2(){

times = new int[300];

hits = new int[300];

}

public void hit(int timestamp){

int index = timestamp % 300;

if(times[index] != timestamp){

// a previous timestamp which has same mod ie: 605 5

times[index] = timestamp;

hits[index] = 1;

} else{

hits[index] ++;

}

}

public int getHits(int timestamp){

int total = 0;

for(int i = 0; i < 300; i++){

if(times[i] > timestamp - 300){

total += hits[i];

}

}

return total;

}

/*

* basic ideal is using buckets.

* 1 bucket for every second because we only need to keep the recent hits info for 300 seconds.

* hit[] array is wrapped around by mod operation.

* Each hit bucket is associated with times[] bucket which record current time.

* If it is not current time, it means it is 300s or 600s... ago and need to reset to 1.*/

}