Event Stream Counter

Data Structures System Design Algorithms

You are given a series of events, each represented as a tuple containing an event type (a non-empty string) and a timestamp (an integer representing seconds since a fixed epoch). Note that events may arrive out-of-order.

Your task is to design and implement a data structure that supports the following two operations:

  1. addEvent(eventType, timestamp): Add an event of the specified type with the given timestamp.

  2. getEventCount(eventType, startTime, endTime): Return the number of events of the specified type whose timestamps fall within the inclusive range [startTime, endTime].

Consider that the system may need to handle up to 10^5 operations (a mix of additions and queries). Optimize your solution for both insertion and query performance.

In addition, implement a program that reads a sequence of commands from standard input where each command is in one of the following formats:

  • add <eventType> <timestamp>
  • query <eventType> <startTime> <endTime>

For every query command, output the result on a new line.

Assume that timestamps are non-negative integers and that events may be added in any order. You may choose the programming language of your choice.