Would an intervier be more likely to pass you if you were clearly recalling a memorized answer? That sounds so worthless... If I was interviewing I would switch to a different question.
A partition method would be part of a larger implementation you still have to reason through and talk through. You just remember that the quicksort of the top half starts at pivot+1 instead of pivot, etc. Essentially you eliminate the little mistakes people tend to make when they are nervous