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Smart prisoners always get a break #2 (Posted on 2007-03-07) Difficulty: 4 of 5
Note: Read this problem carefully, because it's completely different from the original.

As before, 100 prisoners are put into solitary cells, and there's a room with a light bulb. (No prisoner can see the light bulb from his or her own cell.) Every night, the warden picks a prisoner at random, and that prisoner goes to the living room. While there, the prisoner can toggle the bulb if he or she wishes. but this time, the prisoner needs to assert that he knows, which prisoner was in the living room before him. If the assertion is false, all 100 prisoners will be shot. However, if it is indeed true, all prisoners are set free. 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.

But, the prisoners know that after that night, when they will go back to their solitary cells. the warden will choose one prisoner secretly (and this time, not randomly) and will kill him.

What plan should they agree on, so that eventually, someone will make a correct assertion?

See The Solution Submitted by Assaf    
Rating: 4.2500 (12 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Puzzle thoughts Comment 12 of 12 |
Let us number the prosonera as P1, P2, P3, ...etc.
Then, the prisoners must agree between themselves that:
(I)  P(1) will turn on the lights, if he came to the living room after the first day of the meet.
(Ii) P(2) will turn on the light, if he came to the living roommonnthe 2nd day.
(Iii)P(3) will turn on the light if he came on the living room on the 3rd day.
(Iv) If any of the prisoners misses coming onto the living room on the special daye., the prisoners will terminate the process - and, they should begin a new round from the 101th day.

Edited on February 22, 2023, 6:30 am
  Posted by K Sengupta on 2023-02-22 06:22:50

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