Three page path

Given a dataset that represents a user's navigation of a website, find the top N most frequently visited paths. Data The data comes from a web server's access logs where you typically get the following fields: timestamp, IP address, request string, response code, user agent and cookies. For brevity, we provide a dataset that has the user and page parsed out.

User	Page
U1	/
U1	login
U1	subscriber
U2	/
U2	login
U2	subscriber
U3	/
U3	login
U3	product
U1	/
U4	/
U4	login
U4	product
U5	/
U5	login
U5	subscriber

The following words are used to describe the function that needs to be written: Find the top N most popular 3-page paths, where a path is three sequential page visits by a user. The example I use is from U1, where the traversal is: / -> login -> subscriber -> / In the above example, we have two paths:

     1.     / -> login -> subscriber
     2.     login -> subscriber -> /

Expected Output Examples of output for the above example data.

Top 10
/ -> login -> subscribers : 3
/ -> login -> product : 2
login -> subscriber -> / : 1
Top 2
/ -> login -> subscribers : 3
/ -> login -> product : 2

You are recommended to implement the following interface, however you are still free to define your own interface.

public interface TopNPopularPathService { 
    void setup(String[][] data);

    String[] getTopNPopularPaths(int n); 
}

Requirements:

1. Coding should be completed with production like quality.
2. Write at least one positive unit test.
3. Use JDK and common utility lib (e.g. apache-common), introduce too many 3rd libs is not recommended.
4. The program you write can run independently, it should not depend on external application or service.

Build and run

Build

mvn install

Run

mvn test