The eighth post of the series of programming job interview challenge is out. 68 readers provided answers to job interview challenge #7 and most of them had the correct solution. As rvh mentioned, the trick here was to understand that the round table has a symmetric shape and: Actually this algorithm isn’t limited to just a round table. It will work with any shape that is symmetric with respect to both x and y axes. I couldn’t describe the correct answer better than Yoav Zobel, as he was the first one who also formally proved his algorithm:

The Correct answer (as provided by Yoav Zobel):

That’s it, Times up on the sixth in the series of job interview questions. There were 39 people who answered and the first one to give a correct answer was leppie from the IronScheme project.

The correct answer is that both will return false.

You could sum up the answer by saying Boxing.

An ArrayList hold objects, so when you insert a ValueType into it, it will be boxed and become an object. When you compare List[0] to List[1] you are comparing references, and they will never be the same because they are pointing to different objects. This is the reason for getting the false in both comparison. It is true that in the second comparison you are comparing a double and an int ( 2.0 and 2), but that is not why you get false, it is due to the Boxing.