The variable minmax should be declared after the for loop since the min and max will not be modified if the variable is before the for loop.

Actually some mathematical textbooks write the power set of set A as 2^A. If one is familiar with the notion, one writes the answer within one second (if time for typing is not considered).

This kata is a nice selector.

Thanks the author ;-)

You've just solved the kata. Look at the solution staring you in the face.

Don't post code! What is your problem?

Well, that's your job to find out. But as a hint: you should test properly what your method returns.

You may well get the right values in min and max, but your solution is still not correct.