In the programmingzen blog, Antonio Cangiano, a ruby programmer and author of several ruby books, there is a post about an interview for a job at IBM in which the question is to explain how the red-black tree algorithm works.

Hey, I googled for it, here it is: http://programmingzen.com/things-ive-learned-from-hiring-int...

Your comment:

> the question is to explain how the red-black tree algorithm works.

From your link:

> Sample questions included: What’s a Red-Black Tree and what would you use it for?

I don't see how those are equivalent.

I also don't see how the latter two questions are equivalent to asking an interviewee to "balance a red-black tree".

if the numbers are preceded by a space or another symbol your regular expression fails to parse them. You should be more cautious in your assignments.