3 couples (male/female): AX, BY, CZ. Old lady O says: "at least one man is bad!" Let's say only one man, X, is bad --> A knows everyone is good. B,C know X is bad. A would think: damn, it must be my LD. that's the only chance I think everybody is good. (If Y or Z is bad, I would know.) A would kill X that night. But that didn't happen. Nobody died. Therefore our asumption is wrong. i.e., at least two men are bad. Ok, let's say X and Y are bad --> C knows X,Y are bad. A knows Y is bad. B knows X
【在 K****D 的大作中提到】 : 3 couples (male/female): AX, BY, CZ. : Old lady O says: "at least one man is bad!" : Let's say only one man, X, is bad --> : A knows everyone is good. : B,C know X is bad. : A would think: damn, it must be my LD. that's the only chance I think : everybody is good. (If Y or Z is bad, I would know.) : A would kill X that night. : But that didn't happen. Nobody died. Therefore our asumption is wrong. : i.e., at least two men are bad.