From: vibama@cs.hw.ac.uk (Scott Doan)
Newsgroups: soc.culture.vietnamese
Subject: [MISC] Logic puzzles solutions and respond to the self-claimed logicain, LONG NGUYEN
Date: 27 Jul 92 19:07:13 GMT
Organization: Edinburgh, Scotland


Dear SCVers,

Apologise to the netters for having abusing this public domain to send
a message to Long Nguyen. Please hit the DELETE key if you are not 
interested in. BTW, my solution of the logic puzzles
is at the end of this message. I will appreciate it for
all your comments. 

Sincerely,
DDK
----------------------------------------------------------------------
 
Hello Long Nguyen,

I respond right away when your post arrived in the UK ... I do it with
my sincere intention. I wouldn't hold myself to delay the answer as you did
previously. Anyway, delay or not-delay is not a big deal !! Please forget it !!!

In this post, I will first make a few comments on Long Nguyen's posting
and attempt to solve the logic puzzles posed by Long Nguyen (Which book
did you get it from ??? I am curious to know as I don't have time for these
things. My hobby is hanging around the pubs and ..., not with logic
puzzles and your HOW-WHY logic, Long.) BTW, I would be interested in to
know HOW you "become" a logician and WHY you claimed to be one.  

>>I challenge you to prove the following statement:
>>
>Any empty set is a subset of a non-empty set"
>
>This is an unfair test for any body.  DDK has failed to provide needed
>information to make the proof. 

The test wasn't intended for all the netters. I apologise to who take it
seriously. Probably some nettes have felt offended for the such a 
test on net. Again, I repeat it wasn't intended to any netter but Long
Nguyen and whoever claims themselves as a logician.. 
Long Nguyen, as you self-claimed as LOGICIAN, so I thought it was  
good test to see if you can manage to find the solution within a moment.
If you don't, please don't claim yourself as a logician. I am afraid it is
too early to say that. I also wonder WHY you think that a logician is
better than a normal person. HOW does the logician come into the
nonsense stuff of HCM's business ??? Is that right to say something
correctly has to belong to a logician, himself ??

BTW, do you really need more info to prove the statement, the "logician" ??

>I wonder if the test was intended
>to find out WHAT a person knows or HOW a person think.

Neither to find out what a person knows nor how a person thinks.
It tests if you have the cell of maths or logic in your brain or not.
If it takes you more than a minute to find out the answer then
I beg you to reconsider of the intention of becoming the real logican, Long.   
Let's take the SAT or GRE's tests to make a comparision. These tests are
intended to measure your scholastic aptitude and the timing factor is 
crucial when you are taking them. If you have time, you can get
the perfect score but it is rare to see someone achieve it within the limited time.
So timing does matter in these  test. So does the above !!! Lighten up Long !!!

> I DECLINE TAKING THIS TEST! 

Fair enough Long !!! You don't have to shout when you don't want it.
 
> Does it matter if one finds the solution the soonest? 

It does matter in this case as I indicated as above. Your logic puzzles
of the THREE PHILOSOPHERS is a good illustration. Did it say that the 
smartest is the one who understands the problem at the soonest ??? Did
you say this :

"ANYTHING YOU DO/SAY COULD BE USES AGAINST YOU." (Longan).
 
It does go against you now, doesn't it ??? Shame on you !!!
BTW, can you tell me HOW it is going to be against me, not YOU
and WHY it should be against me.
 
 
>What makes one find
>the solution faster than the other?  Faster CPU?  Solving a problem in 1
>second does not mean one has a screaming speed of thinking .  Using the
>hheuristic search in a systematic problem approach, the solution could have
>been any where in the search tree.  A 1 second solution is very much
>indicating that the solution happens to locate at the first level & at the
>cornered most branch where the algorithm starts searching.

Unfortunately, your claim  does not apply in here. The above statement
needs one line to prove it ( I mean the proof core)... It is not major
problem in mathematics whose time complexity is one interstining aspect
to discuss. Introducing the heuristic search in the search tree would
complicate the problem which is itself simple like the above, don't you think ???
Mathematics is to simplify the problem state, not to complicate it.
Don't you get it ???

>Please don't think that Longan is arrogant.  

Who declared himself as the logician of the net then ???
 

>Please don't think that Longan is forcing new ideas on others.

Do you have a new idea anyway ???

------------------------------------------------------------------------
Ok, I will tell two stories to lighten up.

One day, Buddha was about to cross a river to reach a small village
on his tour of teaching.  There was a yoga master seeking to challange
Him.  The master demonstrated his telekinetic ability in flying accross
the reviver with ease and asked if Buddha can do the same.

Buddha pointed to the villagers nearby and preached:
The people all can cross the river with their boats.  Need I show you
HOW to cross a river?

The yoga master then realized that he has been missing the point for so long.

-------------------------------------------------------------------------

	Did you lighten up yourself yet ??? What if you have been behaving like
	the yoga master and your opponent is behaving in the same way 
	the Buddha did ???


-------------------------------------------------------------------------
Story2 is in Co^~ Ho.c Tinh Hoa.

There was a man who devoted much of his life into archery and was very
famous for his archery skill.  He was known for rarely missing the bull-eye
of the target in hundreds of long distance shoots.  And the man was very
arrogant for his reputation.

One day he bragged to an oil peddler about his archery skill.  The oil
peddler discounted the claim, "That is no big deal.  Practice makes perfect.
I've been selling oil for 20 years and have an ability to pore oil through
the small opening in the middle of the coin.  (Ancient coins had holes in 
the middle to get stringed up).

In front of the man's amazed eyes, the oil peddler pored the oil that he's
selling to him through a coin on top a bottle without any spill.  From that
day, the man was no longer arrogant.

---------------------------------------------------------------------------

	What if Long Nguyen is sorta of the archeryman in the story ???
	Did you really comprehend the story ??? 

>I don't exactly know why DDK kept revealing his age on SCV.

Tell me how you work out my real age anyway !!!

>Not addressing to anyone in particular, I would like to point out that, 
>in psychology, the age of wisdom starts about 20 when an individual possesses 
>enough knowledge & experience to determine right/wrong.  A person in the early 
>twenty is much likely to behave as a wisdom infant as compared to another 
>much older person.  

It is true that Long Nguyen in his late 20s is more wisdom
than Long Boy 10 years ago !!! Your addressing is mostly
true when you apply within a person. However, different persons
living in different environment under different conditions
won't have the same level of wisdom and the maturity. Tra.ng
Hie^`n did surprise the Chinese officials for his wisdom at the age of
12. Nguyen Hue was the real general when he led the Ta^y So+n
to conquer Phu' ye^n at the age of 24. Don't you think, you are in the late
20s, can achieve the same level of maturity of Nguyen Hue at 24 ??
Don't take age too seriously. In a way you sound like Calvin
who only knew to call the younger as "Kiddo" in his argument
and fanatically labeled on that youth with bunch of faked facts.
BTW, if you think all the olders are the better than you are,
should you take after Calvin's personal-attack character  who is older 
than you ??? I do respect the older and the saying "Ki'nh la~o , dda('c tho. "
but it does have its limit and exception.

>and wants to introduce his plan to save VN with his logic. What a illogical
>claim !!!                          ^^^^^^^^^^^^^^^^^^^^^^         ^^^^^^^^^

I just meant the plan to save VN is nothing to do with your logic stuff.
That is it !!!
If you are trying to prove my teacher's claim " The Communist is the most
illogical thing" (but I DOUBT IT Long) then it is fine but I said your
claim was illogical because your proof vest is nothing to do with
your logic stuff. Did you read my story about the current british
prime minister John Major ??? Did you get it ???
 
    
Wanna MY OWN solutions of your logic puzzles huh ?? Here goes:

Two Armies:
----------

    Two armies on the same side are seperated by mountains. 
If they combine their forces they will defeat the enemy, if
they attack seperately both armies will be destroyed.  The only
means of communication is by carrier pigeon over the hazardous
mountains.  There is a chance the pigeon will not successfully
make the trip between the armies.

    The general of army A sends the following message to
the general of army B:

    "Let's attack at dawn.  If you agree let me know.  If
        I get no answer I won't attack."

    The pigeon survives the journey and general B agrees
to attack at dawn.  General B thinks as follows:  If the 
2nd pigeon does not survive, general A will think that general 
B never recieved the first message.  So he sends the following 
message to the general of army A:

    "I agree to attack at dawn.  If you recieve this note let me know, otherwise
        I won't attack."
    
The general A recieves this message and composes the following:
    "I recieved your message.  If you recieve this note let me know, otherwise
        I won't attack."

The general B recieves this message and composes the following:

    "I recieved your message.  If you recieve this note let me know, otherwise
        I won't attack."

And so on ad infinitum.

    Is there some way the two generals can compose their messages such that this
infinite loop is avoided?

SOLUTION:
--------

Let A, B be the general of army A and army B respectively. 
A or B can launch an  attack if and only if the following conditions are
satisfied:

(A1) A acknowledges B's agreement to attack at dawn. 
(A2) A's acknowledgement is approved by B.
(B1) B acknowledges A's agreement to attack at dawn. 
(B2) B's acknowledgement is approved by A.

(B1) is obviously satisfied by the the assumption that the pigeon
survives the journey from A to B initially. 

Assume all the messages (after the first one from A to B) contains the 
above paragraph so both A and B know the attack is only launched when A1, A2, 
B1, B2 are satisfied.

My program is designed to solved the problem as follows:
(Interpretation will be provided in person via email request.)

def actions(sender,recipient,goal).

def send(sender,recicipient,goal_list): boolean_value =
        next := goal_list,	
	goal := head(next), 	
	while not(empty(next))  do
	    actions(sender,recipient,goal),
	    next := tail(goal_list), 
       	    goal := head(next)     
	od
        return true
enddef.


/* if the goal_list is [G1,G2,...,Gn] then the corresponding message is
	"G1,G2,...,Gn are satisfied"
*/
  
def launch_attack(). 

def solution() =
  
	while send(B,A,[B1] ) do  
   
       		 while send(A,B,[(A1),(B1)]) do	
		
			while send(B,A,[(A1), (A2), (B1) ]) do
		
				while send(A,B,[(A1), (A2), (B1), (B2)]) do
					launch_attack()
				od
			od

		od

	od

enddef. 

The interesting point comes out my program is :

Can you prove that the program will terminate ???

Program proving is an interesting subject ... it does need some knowledge
of formal specification language as well as some familiarity
with programming language semantics. It is not sensible to 
post such thing on SCV. Anyone wants further discussion then
contact me via email, ukie ...
 
Three philosophers:
--------------------

There very smart guys (Able, Baker and Charlie) are sleeping under a tree
when a flock of pigeons come to roost.  The pigeons do what pigeons doo-doo (sor
ry), and
upon awakening there is bird excrement on the bald pates of all three gentlemen.
No individual guy knows that he has been struck and each thinks it's very funny 
that
the other two gentlemen have been so afflicted.

    The three men laugh long and hard until Able (being the smartest) stops laug
hing.
Soon afterward Baker (being almost as smart as Able) stops laughing and finally
Charlie stops laughing (being less smart than Baker).

    The question is:  How did Able determine that he had bird excrement on his h
ead?
                      How did Baker?
                      How did Charlie?

ANSWER:
------

	o Able thought Baker and Charlie laughed so hard because they thought
	the bird excrement was not on their head, so he derived the bird excrement
	must be on his head. That was why he stopped laughing.

	o Baker knew Able stopped laughing as Able had already known the bird
	excrement was on his head but Charlie still laughed so hard, so it
	must be him who had the bird excrement on his head.`

	o Charlied reasoned if the bird excrement was not on his head then
	Baker might have not laughed right after Able stopped laughing but
	baker still laughed a little longer after Able, so he deduced
        it must be himself who had the bird excrement on his head. 

BTW, Isn't that the smartest the one who found the solution at the soonest, 
Long nguyen.

ta,

DDK