Giant Sudoku near Bristol

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Giant Sudoku near Bristol

Postby jonallen1966 » Thu Jun 30, 2005 12:39 pm

A giant Sudoku puzzle measuring 275ft x 275ft appeared overnight near Bristol
http://news.bbc.co.uk/2/hi/uk_news/england/bristol/somerset/4634471.stm
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Postby tabber » Thu Jun 30, 2005 1:08 pm

Interesting. This would appear to be another advert for Sky One's forthcoming Su Doku programme

See this topic for more.

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Postby scrose » Thu Jun 30, 2005 1:26 pm

It's a shame that such a poorly constructed puzzle (no pun intended) is going to make its way into the Guinness World Records. It has 1905 unique solutions.
Code: Select all
 5 . 6 | . 2 . | 9 . 3
 . . 8 | . . . | 5 . .
 . . . | . . . | . . .
-------+-------+-------
 6 . . | 2 8 5 | . . 9
 . . . | 9 . 3 | . . .
 8 . . | 7 6 1 | . . 4
-------+-------+-------
 . . . | . . . | . . .
 . . 4 | . . . | 3 . .
 2 . 1 | . 5 . | 6 . 7

Edit: Replaced grid image with grid text. Corrected spelling.
Last edited by scrose on Fri Jul 01, 2005 9:35 am, edited 2 times in total.
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Postby scrose » Thu Jun 30, 2005 2:01 pm

Bernard Stay wrote:Solved it?

I've only been able to fill in four cells before getting stuck. I'm still looking to see if the colouring and/or forcing chains techniques will let me get any further.
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Postby Bernard Stay » Thu Jun 30, 2005 2:14 pm

Thanks. Yes, I have 4 filled too. I wasn't sure whether you were serious about the "1905 unique solutions" because if you were the puzzle is de facto insoluble.
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Postby scrose » Thu Jun 30, 2005 2:20 pm

Only a puzzle that has zero solutions is insoluable. The very fact that this puzzle has exactly 1905 solutions, means that it can be solved. Whether any of those solutions can be reached without guessing is entirely another matter.
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Postby Bernard Stay » Thu Jun 30, 2005 2:34 pm

Yes, well, it all depends on how you define 'insoluble'. I would only accept a puzzle at all if it has a single unique solution, otherwise I believe it can justifiably be said to be insoluble; or, with the best will in the world, not worth bothering with.
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Postby scrose » Thu Jun 30, 2005 2:40 pm

Bernard Stay wrote:Yes, well, it all depends on how you define 'insoluble'.

insoluable: having or admitting of no solution or explanation
This puzzle has multiple solutions, each of them can shown, and a chain of reasoning can be provided for each.

Bernard Stay wrote:...with the best will in the world, not worth bothering with.

:DI agree with you there! This puzzle is a disgrace. I hope a public apology is forthcoming from Sky One.
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Postby Bernard Stay » Thu Jun 30, 2005 6:44 pm

Insoluable: having or admitting of no solution or explanation
This puzzle has multiple solutions, each of them can shown, and a chain of reasoning can be provided for each.


Dictionaries are all very well, but:

Take the question: "Who lives in a house?". It has an innumerable number of answers, therefore it is unanswerable. Similarly, a Su Doku that has hundreds of possible solutions is insoluble.
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Postby scrose » Thu Jun 30, 2005 6:58 pm

Bernard Stay wrote:Take the question: "Who lives in a house?".

I don't think that's an accurate analogy. "Who lives in this house?" would be more accurate (and answerable). We aren't questioning the solubility of sudoku puzzles in general; we are only examining this particular one.

Bernard Stay wrote:Similarly, a Su Doku that has hundreds of possible solutions is insoluble.

I disagree. Using angusj's solver, I came up with this solution in under thirty seconds by making a total of eight guesses. Quite soluble.

Code: Select all
 5 1 6 | 4 2 7 | 9 8 3
 4 2 8 | 3 9 6 | 5 7 1
 3 7 9 | 5 1 8 | 4 2 6
-------+-------+-------
 6 4 7 | 2 8 5 | 1 3 9
 1 5 2 | 9 4 3 | 7 6 8
 8 9 3 | 7 6 1 | 2 5 4
-------+-------+-------
 7 6 5 | 1 3 4 | 8 9 2
 9 8 4 | 6 7 2 | 3 1 5
 2 3 1 | 8 5 9 | 6 4 7

Like you said, and as I have already agreed, this puzzle (soluble or insoluble) is not worth bothering with.

Update: So much for not bothering with it! Using rubylips' solver, I was able to generate all 1905 solutions in just under 15 seconds (even on my old clunker P3 500MHz). I can send the solutions as a private message to anyone who is interested in entering them into the contest for the £5000. (Sadly, I'm not eligible since I do not reside in the UK.)
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Giant Sudoku near Bristol

Postby AMcK » Fri Jul 01, 2005 1:37 am

I make it 954 unique solutions, using trial & error, but I could be wrong.
Clearly they are all "solutions" but, in my understanding, a well-formed sudoku puzzle is one with a unique solution that can be derived entirely by logic.
The Giant Sudoku near Bristol is in this sense a poor advertisement of the genre. It has also wasted me a lot of time.
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Postby simes » Fri Jul 01, 2005 7:53 am

I make it 1905 solutions too.
Last edited by simes on Sun Dec 11, 2011 10:17 am, edited 1 time in total.
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Postby tabber » Fri Jul 01, 2005 9:09 am

I wonder how they will determine the correct answer for this competition? Do you get entered if you pick any one of the plethora of correct solutions? Or are they expecting the one that the creator thought was correct.

The show is on tonight, I wonder if they will mention this puzzle. The title of the show appears to suggest it is Live, so they could put the record straight. Surprised Carol hasn't pulled out after poor old Mr.Whitely's sad demise. She must be made of strong stuff, good on her.

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Postby su_doku » Fri Jul 01, 2005 11:13 am

The celebrity is dead long live the celebrity!
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Postby tabber » Fri Jul 01, 2005 4:15 pm

In fact, not only does it have nearly 2000 solutions, but there are a couple of other stupid things as well. It says "Simply print off the grid, and complete it and send it in".

1. If you print off the grid using the supplied Print button, all the squares are black, so unless you use a white pen, they are not going to show up.
2. It is called an 'Online competition', but you have to post your correct entry, you don't appear to be able to send it to an email address. Hardly 'online'.

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