Solution - YouTube video explanation     
Solution - Blog with complete code
Solution 2 - Blog with slightly different explanation

Write code for low level design (object oriented design) of a webpage visits counter.
There are n webpages in a website numbered 0 to n-1.
Hundreds of users visit webpages of this website simultaneously.
You have to record visit count for each page and return them when required.

Note :
- Your code will be tested in a MULTI-THREADED environment, so use thread safe data structures and handle synchronization properly.
- There will be at max 1000 webpages

Your solution should implement below methods :

Method : init(int totalPages, Helper06 helper)
- totalPages is the 'n' we discussed above i.e. total number of webpages in the website.
- Use this method to initialize your instance variables
- use helper's methods for printing logs else logs will not be visible.

Method : incrementVisitCount(int pageIndex)
- increment visit count for webpage at pageIndex by 1.

Method : getVisitCount(int pageIndex)
- return total visit count for a given page

For the same pageIndex, incrementVisitCount() and getVisitCount() will never be called concurrently.
This is done to maintain correctness and eventual consistency in the system.

Example :
init(totalPages = 2, helper = helper)

incrementVisitCount(pageIndex = 0)
incrementVisitCount(pageIndex = 1)
incrementVisitCount(pageIndex = 1)
incrementVisitCount(pageIndex = 1)
incrementVisitCount(pageIndex = 0)

getVisitCount(pageIndex = 0) : returns 2
getVisitCount(pageIndex = 1) : returns 3