use'while', not'if'

Hey! nadolski's explenation is much better than I could give at the moment as I'm new to regex and this one is partially taken from stack overflow and partialy changed by me!

Good solution, but it must be like this: /.+//|www\.|..+/g ("\" after "www"). Because the URL "http://www4cnet.com" will reutrn 'cnet' instead of 'www4cnet'.

The moment i saw the question i understood i had to use regex but i am not good at it, probably scared of the syntax. But this looks good and i will definitely check the solution.

The tests are fine. Please post your code with spoilers and raise this kind of problems as a question next time :)

you can't remove items from a list that you are itterating over. need to create a copy of that list. (NOTE: copy, not simply set c = a, cuz that will just point to the same list twice.

√-1 = i

i is a complex number. You cannot square root a negative number - otherwise it ends up being a complex number (imaginary). You must check if n >= 0

. . . and concerning the 1 dan grade I think we can say "Congrats!" to you.

; ) )