Leetcode:design hit Counter

Design a hit counter which counts the number of hits received in the past 5minutes. Each function accepts a timestamp parameter (in seconds granularity) and your may assume that calls is being made to the S Ystem in chronological order (ie, the timestamp is monotonically increasing). Assume the earliest timestamp starts at1. It is possible this several hits arrive roughly at the same time. Example:hitcounter counter=Newhitcounter ();//Hit at timestamp 1.Counter.hit (1);//Hit at timestamp 2.Counter.hit (2);//Hit at timestamp 3.Counter.hit (3);//get hits at timestamp 4, should return 3.Counter.gethits (4);//Hits at timestamp.Counter.hit (300);//get hits at timestamp, should return 4.Counter.gethits (300);//get hits at timestamp 301, should return 3.Counter.gethits (301); Follow Up:whatifThe number of hits per second could be very large? Does your design scale?

Use Queue

1  Public classHitCounter {2Queue<integer>queue;3     4     /**Initialize your data structure here.*/5      PublicHitCounter () {6Queue =NewLinkedlist<integer>();7     }8     9     /**Record a hit.Ten         @paramtimestamp-the current timestamp (in seconds granularity).*/ One      Public voidHitinttimestamp) { A          while(!queue.isempty () && Queue.peek (). Intvalue () +300<=timestamp) { - Queue.poll (); -         } the Queue.offer (timestamp); -     } -      -     /**Return the number of hits in the past 5 minutes. +         @paramtimestamp-the current timestamp (in seconds granularity).*/ -      Public intGethits (inttimestamp) { +          while(!queue.isempty () && Queue.peek (). Intvalue () +300<=timestamp) { A Queue.poll (); at         } -         returnqueue.size (); -     } - } -  - /** in * Your HitCounter object would be instantiated and called as such: - * HitCounter obj = new HitCounter (); to * Obj.hit (timestamp); + * int param_2 = obj.gethits (timestamp); -  */

Better Solution:can solve follow up, refer to https://discuss.leetcode.com/topic/48758/ super-easy-design-o-1-hit-o-s-gethits-no-fancy-data-structure-is-needed

Basic ideal is using buckets. 1 bucket for every second because we only need to keep the recent hits info for seconds. Hit[] Array is wrapped around by mod operation. Each of the hit buckets are associated with times[] buckets which record current time. If It isn't current time, it means it was at least 300s or even longer time ago and need to reset to 1.

1  Public classHitCounter {2     int[] time;3     int[] hits;4 5     /**Initialize your data structure here.*/6      PublicHitCounter () {7Time =New int[300];8hits =New int[300];9     }Ten      One     /**Record a hit. A         @paramtimestamp-the current timestamp (in seconds granularity).*/ -      Public voidHitinttimestamp) { -         if(time[timestamp%300]! =timestamp) { theTIME[TIMESTAMP%300] =timestamp; -HITS[TIMESTAMP%300] = 1; -         } -         Elsehits[timestamp%300]++; +     } -      +     /**Return the number of hits in the past 5 minutes. A         @paramtimestamp-the current timestamp (in seconds granularity).*/ at      Public intGethits (inttimestamp) { -         intres = 0; -          for(inti=0; i<300; i++) { -             if(Time[i]+300 >timestamp) { -Res + =Hits[i]; -             } in         } -         returnRes; to     } + } -  the /** * * Your HitCounter object would be instantiated and called as such: $ * HitCounter obj = new HitCounter ();Panax Notoginseng * Obj.hit (timestamp); - * int param_2 = obj.gethits (timestamp); the  */

Leetcode:design hit Counter