C/C++ :: Iterating Over Either Row Or Column?

Suppose I want to represent an apartment building in terms of floors and rooms with a single data object. Each floor has the same number of rooms at any given time. During the course of the program, I will need to change the number of floors occasionally and will need to change the number of rooms on each floor occasionally. (Don't worry about the building permits needed to do this.)

Now, I also want to be able to iterate over either each floor (think "row") or each room (think "column"). For example, I might want to program the equivalent of "Johnson, go fix all the front doors on the 8th floor" or the equivalent of "Johnson, go fix all the front doors to room B on each floor". (Yeah, I know, for the latter I could iterate over each floor and then access room B but that doesn't feel as "clean" as being able to iterate over a separate room/column.)