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 Post subject: who ownes the zebra
PostPosted: Fri Mar 08, 2013 1:12 pm 
Level 1 Cleric

Joined: Mon Aug 31, 2009 11:21 am
Posts: 12
Location: zaanstad NL
i want to solve this by computer :
Quote:
''1.There are five houses.
''2.The Englishman lives in the red house.
''3.The Spaniard owns the dog.
''4.Coffee is drunk in the green house.
''5.The Ukrainian drinks tea.
''6.The green house is immediately to the right of the ivory house.
''7.The Old Gold smoker owns snails.
''8.Kools are smoked in the yellow house.
''9.Milk is drunk in the middle house.
''10.The Norwegian lives in the first house.
''11.The man who smokes Chesterfields lives in the house next to the man with the fox.
''12.Kools are smoked in the house next to the house where the horse is kept.
''13.The Lucky Strike smoker drinks orange juice.
''14.The Japanese smokes Parliaments.
''15.The Norwegian lives next to the blue house

''who ownes the zebra ?

i cant use brute force
this has pow( 5! , 5 ) = 24883200000 posebilities

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 Post subject: Re: who ownes the zebra
PostPosted: Fri Mar 08, 2013 8:19 pm 
Grand Optimizer

Joined: Sun Oct 16, 2011 3:09 pm
Posts: 367
Location: Here (where else?)
Indeed, a much better strategy is to use the clues directly, and use logic deduction, much like we do.
eg Englishman <-> red house

-> not Englishman <-> green house
not Englishman <-> ivory house
not Englishman <-> yellow house
not Englishman <-> blue house
not Spaniard <-> red house
not Ukrainian <-> red house
not Japanese <-> red house
not Norwegian <-> red house

It's a fun puzzle to figure out how to program deduction

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 Post subject: Re: who ownes the zebra
PostPosted: Fri Mar 08, 2013 9:34 pm 
Dexterous Droid
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Joined: Wed Aug 18, 2004 7:40 pm
Posts: 3825
Location: South Africa
This would be much easier to solve with pen and paper. But I'll take a crack at the groundwork.

I would start out with identifying the kinds of logical relations.
  • x implies y
  • x is next to y
  • x to the right of y
  • x is in house number i
Then one needs to identify what house attributes are available and their possible values.
  • colour: red green blue yellow ivory
  • pet: dog snail fox horse [implied zebra]
  • smoke: Old Gold, Kools, Chesterfield, Lucky Strike, Parliaments
  • drink: coffee tea milk OJ [implied gin & tonic, obviously]
  • nationality: English, Ukrainian, Spanish, Norwegian, Japanese
From the standpoint of the puzzle, houses are an array of containers for the above attributes (house number, colour, etc).

The first step is to put down things that can't change, the rules which specify house number should be applied as well as any that can be directly applied (in this case just that the blue house is next to the Norwegian, there aren't any other direct relations).
Code:
number                  |   1             |   2             |   3             |   4             |   5             |
colour                  |                 | blue            |                 |                 |                 |
pet                     |                 |                 |                 |                 |                 |
smoke                   |                 |                 |                 |                 |                 |
drink                   |                 |                 | milk            |                 |                 |
nationality             | norwegian       |                 |                 |                 |                 |


The puzzle doesn't have any other rules we can apply directly so we need to eliminate the possible options in each cell until only 1 option remains. Referring to our logical relations, the ways of eliminating options are:
  • x implies y: (1) eliminate x from all houses that are not y, vice-versa for y.
  • x is next to y: (1) where either x or y is known, eliminate the other from all cells not next to the known one.
  • x to the right of y: (1) eliminate x where a value to the left is known to be not y. eliminate y where a value to the right is known to be not x. (2) eliminate y from all the right-most houses, eliminate x from all the left-most houses

There might be a bunch of others but from here you can infer
1. house 1 has the norwegian, so by the first rule we can eliminate all the options involving nationality. -red, -tea, -parliament
2. eliminate green from house 1 because it's the left-most house.
3. eliminate ivory from hosue 1 because it's to the left of a known blue house.
3. the only colour left is yellow, so the first house is yellow.

If you carry on eliminating options then you should arrive at a solution. You just need to make sure that the list of methods to eliminate options is complete. So the general algorithm is:
Code:
while there are still unkown values in houses
{
   check if any of the rules can be applied directly, without inference
   eliminate potential values from all the houses until one of the attributes only has 1 possible value left
}

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 Post subject: Re: who ownes the zebra
PostPosted: Fri Mar 29, 2013 5:38 am 
Technomaniac

Joined: Sun Dec 05, 2004 11:27 am
Posts: 3252
Location: Sydney, Australia
Just looking at the clues, there is no indication that anyone owns a zebra. Are you sure this isn't a trick question?

If you are looking for an interesting programming language for this sort of thing, have a look at prolog. It should let you do something which will mean that each clue translates fairly directly into the language, and then you can ask it questions (like who owns the zebra) and it will give you an answer (or tell you that it can't work out the answer from the clues)

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 Post subject: Re: who ownes the zebra
PostPosted: Fri Mar 29, 2013 1:06 pm 
Dexterous Droid
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Joined: Wed Aug 18, 2004 7:40 pm
Posts: 3825
Location: South Africa
Andy wrote:
Just looking at the clues, there is no indication that anyone owns a zebra. Are you sure this isn't a trick question?

You're right. It should have stated, "given that someone owns a zebra, who is it?". There's also an unkown drink.

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 Post subject: Re: who ownes the zebra
PostPosted: Thu Apr 04, 2013 9:09 am 
Postronaut

Joined: Sun Mar 10, 2013 3:32 pm
Posts: 45
i own a zebra..


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 Post subject: Re: who ownes the zebra
PostPosted: Thu Apr 04, 2013 5:28 pm 
BANNED

Joined: Sun Jun 24, 2012 12:49 am
Posts: 504
Hey, I was going to say that! I own the Zebra!


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 Post subject: Re: who ownes the zebra
PostPosted: Fri Apr 05, 2013 5:43 pm 
Bytewise
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Joined: Sun Aug 05, 2012 9:32 pm
Posts: 276
From what i can tell by looking at the clues, there are 5 houses, and 4 animals mentioned, if you figure out who owns what, you will find out who owns the zebra

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 Post subject: Re: who ownes the zebra
PostPosted: Sun Apr 07, 2013 9:17 pm 
Bytewise
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Joined: Sun Aug 05, 2012 9:32 pm
Posts: 276
So did you manage to make the algorithm for finding out who owns the zebra? I am really thrilled to know the answer :D I think its the Norwegian, he seems like the type that would steal a zebra from a ZOO

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