[Hjelstrom]

Since you're already sorting the problems into numerical order, you could just eliminate duplicates as you print out the list: "If the number I'm about to print is the same as the one I printed last time through the loop, just skip it".

There are other ways to generate your list that won't create duplicates. How about this, create an array of all of the possible questions, then do 'n' random swaps inside this array, then read however many questions you want from the start of the list. (essentially "shuffle" the list and then take the top 'n')

Or, create said array, and randomly pull questions out of the array (using rand to create an index in to the array). As you take a question, over-write that array entry with -1 and whenever you try to pull an entry that has -1 in it, re-roll another random index. (this probably isn't a great approach...)

If you really need to take a set of data and efficiently eliminate duplicates, you can use std::set but I'd recommend doing without that until you learn more of the basics.