Java abstraction-Teacher's birthday-logical thinking-interesting face test-ground tornado

(-1) write in front

Have to go to Beijing, abruptly to arrange a Java exam, for those special details of the things I forget it also do not feel anything bad, remember before, also have seen, but usually not commonly used connection broken, but you rote is useless, a period of time or will forget, the only way is to do more things, Theory with practice, on the contrary, I feel very interesting, but also on the internet to see a lot of explanations, feel that there are shortcomings, the following is my answer.

(0) Detailed explanation

Set up a teacher's birthday for M-month N-day. Tell the student a (that is, the month that the student knows the teacher is born) and tell the student B (that is, the student B knows the day the teacher was born). The following dates are available: March 4, March 8, March 10, June 4, June 7, September 1, September 10, December 1, December 2, December 8

One of them is the teacher's birthday.

Current student a dialogue with Student B:

Student A: If I don't know, you must not know.

Student B: I don't know, now I know.

Student A: I know that, too.

Now ask: What day is the teacher's birthday?

The first sentence of a

First we look at the characteristics of the data, the data is composed of the month and date, A is aware of the month, the data of the month is 3,6,9,12, a can not be known by the month information of the teacher's birthday, a know that B can not be inferred from the date of the correct month.

A know is the March date has 4,8,10

A known June date is 4, 7

A know is the September date has 1,10

A know is the December date has 2,8

We found 7th, 2nd is the only, also shows that if a know is June, then B know is 7th, guess the birthday, a will not say you must not know, so a know is not June, similarly, a know is not December.

The first sentence of B

According to the first sentence of a, the remaining data are as follows:

A know is the March date has 4,8,10

A know is the September date has 1,10

B in the first half of the sentence there is ambiguity, a case, B think a can be introduced through the month birthday, then the date of B is 2 or 7, which is inconsistent with the conclusion of the first sentence. Then is the second case, b at this time through a words inferred from the above conclusion, according to their own date to judge a month, obviously 10 is wrong, if it is 10, a month is not the only. Then the data is as follows:

A know is the March date has 4,8

You know, the September date is 1.

This seems to be possible March 4, March 8, September 1, because B knows that any of the corresponding months in 1,4,8 is unique.

The second sentence of a

This sentence to the answer to the September 1, because for a, if he knows the March, for the teacher's birthday on March 4 and March 8 two options, and if he knew September, only September 1 this kind of answer.

Java abstraction-Teacher's birthday-logical thinking-interesting face test-ground tornado