June 28, 2013
Today’s exercise is a delightful little programming puzzle:
Write a function
f(f(n)) = -nfor all integers n.
When I first saw this puzzle, it took me two days before I had the necessary flash of inspiration, then about two minutes to write. Do yourself a favor and don’t peek at the suggested solution until you figure it out yourself.
Your task is to write function
f as described above. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.