SICK DOGS

50487 · 发表于 2019-5-9 11:48:33

There are 50 families living in a big yard, each with a dog. The people in this Yard have strong reasoning ability. One day they were told that a dog was sick in the yard and asked all owners to shoot him the day they found out his dog was sick. However, all the owners and their dogs can not leave their house, nor can they communicate with each other in any way. All they can do is to observe the sickness of other people's dogs through the window to judge whether their dogs are sick or not. (That is to say, each owner can only see whether the other 49 dogs are sick or not. It is impossible to see his own dog alone.)
The first day there was no gunshot, the second day there was no gunshot, the third day there was a burst of gunshot, asked how many dogs were shot?

别用翻译！！！

81845 · 发表于 2019-5-9 12:00:05

病狗问题，和红眼问题一样，本质上是共识问题。引入一个概念，常识，即大家都能观察到。用Ri表示至少有i条病狗，假设在第i天，Ri是常识，如果此时没有任何一个主人能分辩自己的狗是不是病狗，那么Ri+1必然成立，因为每个人至少看到有i条病狗，如果小于i那自家的就是病狗了，如此枪声必然同一天响起。则第k天有k条病狗会成为一个常识。

21457 · 发表于 2019-5-9 11:49:37

改编难道是指从中文改编成英文？

45001 · 发表于 2019-5-9 12:11:44

不让人翻译那就只是考英语水平？

也是老题目，3只狗

74088 · 发表于 2019-5-9 12:21:06

不能翻译…那看不懂怎么办…

89833 · 发表于 2019-5-9 13:26:11

这可是我们这届当年一个重点中学小升初的一个题

85759 · 发表于 2019-5-9 13:42:07

3条
如果是一条狗的话，那当天狗主人就会处决它，但第一天并没有枪声，
如果是两只的话，他们两家都会知道自己家的狗是病狗，那么，第二天就应该处决，但没有
如果是4只的话，每个人都会看到3只或4只病狗，但不确定到底是多少只病狗，所以第三天应该也不会有枪声，所以应该是3只吧

79403 · 发表于 2019-5-9 14:49:23

看的不是很懂

85815 · 发表于 2019-5-9 20:44:43

three dogs.
If there is only one dog,the owners'd kill it ai the first day because they didn't see a seck dog.But in the first day nobody'd killed their dogs.
If there are two dogs,for nobody had killed his dog,the families must have know there's two dogs.So the families who can only see one sick dogs would kill their dogs.But in the second day nobody'd killed their dogs either.
On the third day,everyone knew that there're at least three dogs,so the families who can only see two sick dogs killed their dogs.
Accroding to what I've said,there's three dogs.
over.

61970 · 发表于 2019-5-9 23:31:12

第n天枪响，就有n条狗

[逻辑推理] SICK DOGS