Von Neumann was the subject of many dotty professor stories.  Von
Neumann supposedly had the habit of simply writing answers to homework
assignments on the board (the method of solution being, of course,
obvious) when he was asked how to solve problems.  One time one of his
students tried to get more helpful information by asking if there was
another way to solve the problem.  Von Neumann looked blank for a
moment, thought, and then answered, "Yes.".