Problem bank
Problem 28 of 333HardBrainteaserP028
Prisoners and the light bulb
100 prisoners are taken into solitary cells. There is a room with one light bulb (initially off). A guard picks a prisoner uniformly at random (with replacement) each day, who visits the room and may toggle the bulb. At any time a prisoner can declare 'we have all visited the room.' If correct, all go free; if wrong, all die. Prisoners can strategize beforehand. Design a winning strategy.
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