On Mar 7, 2013, at 9:00 PM, GS Chandy <firstname.lastname@example.org> wrote:
> Your 'simpler version' is just plain and simply wrong. Read the puzzle more carefully.
Well, I did miss the lighter or heavier clause, however, that is not the crux of the problem. The crux is to do it in 3 steps. Without much effort, a binary tree strategy will get down to 4, even with the condition of not knowing whether the counterfeit coin is heavier or lighter. The trick is to combine the two inner most steps into one such that you determine if the counterfeit coin is heavier or lighter and also end up with just 3 coins left (because that can be solved in one more step).