regex replace

[Gary Wessle]

Hi

I need to remove the "//" from the beginning of all the lines in my
c++ code which contain the string 'n', including the single comma.
e.g, un-comment all of those lines that qualify. and then also to
place "//" not including the double quotes at the beginning of all
lines containing the 'f' string.

this is a bit too much for me to come up with. 

thanks