It is time to review the algorithm again. I posted the question more than 5 month ago, the link is here.
I had a mock interview and the peer chose to use C++ language. I did some research how to translate those four lines of C# code to C++ language.
I just could not believe that one day I can write a product using C# advanced feature like LINQ, write regular expression and groupby clause and where clause. I am so excited to set a small goal for my next project.