An
old chestnut goes like this:
You have two identical drinking glasses. You know that these
glasses will break if dropped from floor N of a 100 floor building or
any higher floor, but they will not break if dropped from any lower floor.
N is an unknown integer from 1 to 101.
You are asked to devise a plan to determine N, minimizing the possible
number of drops under the plan. (Not the average number; you're trying
to minimize the number of drops in the worst-case scenario.) Note that
you may retrieve a dropped, unbroken glass and drop it again, but you may
not reuse a broken glass, and the plan must determine N in all cases,
so if the second glass breaks, this information must be enough for you to
determine N.
Answer