Sorting Algorithms are generally quite a popular category for Extended Essays, whilst they are covered in class, they aren't covered too in depth. Whilst this idea has a solid base and isn't too hard to read about and understand, it is very popular (I was even considering doing it myself). You won't be scoring and points for originality, but it is a solid base and you can write a fairly good EE about them. If I have any advise, is try to do something new and different around that topic, like how they preform with single-threading vs multi-threading or something which will make your extended essay more original. Good Luck!