With an IQ of 110 you can do it.
You need to spend a year or two learning C++ with a good textbook. I would recommend:
Learn Professional Programming Skill in C++ Programming Language by Adalat Khan
and
Object-Oriented Programming in C++ by Nicolai M. Josuttis
If you master these two books you will be fine regarding C++ but you may need a bit more knowledge regarding networking programming, and concurrent programming with threads, for understanding p2p technology, namely discovering network nodes using IRC, sockets, etc.
To score very high in a Mensa IQ exam you need an entremely good vocabullary, which you don't need to master C++ coding and you need to be good with pattern recognition and brain teasers that although may tell a lot about how sharp and fit your brain is, how quick, focused and able to memorize you are, and for that matter how intelligent you are, will not actually be decisive in your ability to understand bitcoin and its code.
What you need is the
chance of getting to know the best resources and to dedicate enough time to them.
First you need to understand bitcoin, generally.
1) Watch "United Colors of Bitcoin" on youtube a few times,
jotting down notes, until you get it. Five times may be enough.
http://www.youtube.com/watch?v=p6sOFXHlhuE2) Consolidate your knowledge with a more detailed and technical
explanation with the video: How Bitcoin Works Under the Hood.
http://www.youtube.com/watch?v=Lx9zgZCMqXEWatch it also as many times as necessary, after you are confident
you did understand quite a lot of the previous video.
3) Then you need to understand the code.
Buy these two books on amazon: Learn Professional Programming Skill in C++ Programming Language by
Adalat Khan and Object-Oriented Programming in C++ by Nicolai M. Josuttis
Focus on the first book. Dedicating two hours of reading it a day, for a few months.
If you dedicate two hours a day, by March or April your C++ will be fine to grasp the
code.
In the meantime print the 12,222 lines of code of the original
client code
http://www.scribd.com/doc/189139502/Bitcoin-12-222-lines-of-code(files: base58.h, bignum.h, db.cpp, db.h, headers.h, irc.cpp, irc.h, key.h, main.cpp, main.h, market.cpp, market.h, net.cpp, net.h,
script.cpp, script.h, serialize.h, ui.cpp, ui.h, uint256.h, util.cpp and util.h) and get familliar with it, having a mental picture of it and of the line numbers - as clearly as possible.
The different pieces of the puzzle will start to couple and in a year or two you will understand it all. And you don't need a high IQ. With a 110 IQ you are fine.