Simple elimination:紅桃A、Q、4 黑桃J、8、4、2、7、3 梅花K、Q、5、4、6 方塊A、5 Init: {HA, HQ, H4, SJ, S8, S4, S2, S7, S3, CK, CQ, C5, C5, C6, DA, D5} 1. P: 我不知道这张牌。 S2, S3, C6, S7, S8, SJ, CK are eliminated. (If not, P will know it as there numbers have single appearance) Pool: {HA, HQ, H4, S4, CQ, C4, DA, D5} 2. Q:我知道你不知道着张牌。 S4, CQ, C4 are eliminated (If not, Q will not know P don't know it as only Spade and Club have those who have single appearance) Pool: {HA, HQ, H4, DA, D5} 3. P:现在我知道这张牌了。 HA, DA are eliminiated (If not, P will not able to know it as A have appearance for both Heart and Diamond) Pool: {HQ, H4, D5} 4. Q:我也知道了。 HQ, H4 are eliminated (If not, Q will not know it as only diamond have only one appearance now.) Answer: Diamond 5