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Can it be solved using probabilities? I mean, if, for example, the Guru says 'I see nobody on this island who has blue eyes', then the whole 100 brown-eyed people can pack and leave at once. If the Guru says 'I see at least one blue-eyed person' AND thereare two BE present, neither of them leaves that night and so next morning they both know they are BE and can leave the following night, and so on?
The approach you describe is sensible, but I don't see what it has to do with probabilities; all the probabilities involved are either 0 or 1.