Robert Hansen (RH) posted Mar 8, 2013 9:23 AM: > > On Mar 7, 2013, at 9:00 PM, GS Chandy > <email@example.com> 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). > > Bob Hansen > You sure did miss the "lighter" or "heavier" clause!
But it's no real "trick" at all.
It was successfully done in 3 steps by Joe Niederberger (JN) when he was around 10 years old. And by the underigned when he was 10 or 11 years old. I guarantee you neither JN nor GSC used "binary search" or "exhaustive search" or anything of the sort. Those terms were not even imagined (or imaginable) by either of us at the time. What was actually used was the 'question-asking frame of mind' that is inherent in every real learner.
All your talk about "binary search" and "exhaustive search" [or even "stochastic search algorithms", if you should happen to come up with that, next, in order to try and wriggle out of the hole you've dug for yourself] - it's all just so much bumpf, I'm afraid.