Easy
Implement RecentCounter that counts recent requests within a time window. Implement ping(t) which records a request at time t (in milliseconds) and returns the number of requests that happened in the inclusive range [t - 3000, t]. Every call to ping uses a strictly larger t than the previous call.
Input: operations = ["RecentCounter","ping","ping","ping","ping"], values = [[],[1],[100],[3001],[3002]] Output: [null,1,2,3,3]