100 prisoners are put into solitary cells. There's a central living room with one light bulb; the bulb is initially off. No prisoner can see the light bulb from his or her own cell. Every day, the warden picks a prisoner at random, and that prisoner goes to the central living room. While there, the prisoner can toggle the bulb if he or she wishes. Also, the prisoner has the option of asserting the claim that all 100 prisoners have been to the living room. If this assertion is false (that is, some prisoners still haven't been to the living room), all 100 prisoners will be shot for their stupidity. However, if it is indeed true, all prisoners are set free and inducted into MENSA, since the world can always use more smart people. Thus, the assertion should only be made if the prisoner is 100% certain of its validity.
The prisoners are allowed to get together one night, to discuss a plan. What plan should they agree on, so that eventually, someone will make a correct assertion?
(In reply to re(2): An impractical solution...
Actually, I stand by my analogy. I think of the wetware as harddrive space - the data there needs to be loaded into RAM to be transfered to other parts of the system.
The only "shared" memory in this system is the one lightbulb - which is either on, or off. Once a prisoner enters the room, the "data" of the lightbulb is "written" to their wetware storage. They also have an option of changing the shared bit of RAM.
Posted by levik
on 2002-08-27 09:24:57