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Brainteaser thread
http://www.rcbroughton.co.uk/sudoku/forum/viewtopic.php?f=17&t=32		 Page 10 of 14
Author:  udosuk [ Tue May 20, 2008 8:58 am ]
Post subject:  Re: Brainteaser thread
Richard has gone to vacation already? :scratch:

Was asking if he could check whether the 21 shafts as {1,2,...,21} would produce any plausible solution... :?:
Author:  Glyn [ Tue May 20, 2008 9:44 am ]
Post subject:  Re: Brainteaser thread
Richard on vacation. :naughty: Oh well that gives us all a chance to catch up :) , hope he's left a machine running to complete the task. :whistle:

Matt I take it that a complete sequence of shafts from 1 through to 21 was not the solution you had then.
Author:  rcbroughton [ Tue May 20, 2008 5:32 pm ]
Post subject:  Re: Brainteaser thread
Hope to see a solution waiting for me on my pc when I get back on 30th.

Only have mobile phone browser until then.

Plenty of time for someone else to find a solution.

Hasta luego ! My paella and cerveza is waiting for me
Author:  rcbroughton [ Fri May 30, 2008 4:57 pm ]
Post subject:  Re: Brainteaser thread
Good News & Bad News I'm afraid.

Good News, I'm back from vacation and will start to catch up on some of the posting that's been going on . .

Bad News . . . Having left my Golden Rods calculator running for 10 days and it having now tried over 261,752,700,000 possibilities, we still have no hits. I know the logic is sound - it finds even 4 rod solutions in seconds - so must be a very well hidden solution - maybe it is unique!

If anyone wants to put some CPU power into the solution, I could distribute the solver and we could all start from different points (even this far into the possibilities, we are still only at a first rod of {1,2,4,11,29,4} and [Edit:] trying rod 2 combinations starting with 20.
Rgds
Author:  udosuk [ Sat May 31, 2008 4:01 am ]
Post subject:  Re: Brainteaser thread
I definitely know the existence of one solution, and remember the source has claimed it being unique (I've lost the link to the source however, and can't google it up anymore :brickwall:).

Richard, is it possible to ask your solver to separately run on another search using {1..21} as the lengths of the 21 shafts? I don't think it would take too long. :salute:

Or if you don't mind upload your solver up for us to try ourselves. :pirate:
Author:  rcbroughton [ Sat May 31, 2008 8:12 am ]
Post subject:  Re: Brainteaser thread
udosuk wrote:
I definitely know the existence of one solution, and remember the source has claimed it being unique (I've lost the link to the source however, and can't google it up anymore :brickwall:).

Richard, is it possible to ask your solver to separately run on another search using {1..21} as the lengths of the 21 shafts? I don't think it would take too long. :salute:

Or if you don't mind upload your solver up for us to try ourselves. :pirate:
On a separate machine, I'm currently trying out limiting the shafts to 1..21, picking up on your hint. No hits yet

[Edit] . . . and since we didn't see a 1..n solution for 4 or 5 rods, I'm not holding my breath for a 1..21 solution
Author:  rcbroughton [ Sun Jun 01, 2008 12:30 pm ]
Post subject:  Re: Brainteaser thread
First solution has dropped out of the search: (and it doesn't use 1 ... 21)

{1, 4, 25, 6, 14, 3} {8, 10, 16, 12, 9} {2, 22, 19, 13} {7, 33, 11} {15, 27} {39}

Still looking for more . . .

Rgds
Richard
Author:  udosuk [ Sun Jun 01, 2008 1:54 pm ]
Post subject:  Re: Brainteaser thread
Well done Richard! Bow to you! ;clapclap; :applause: :thumbs:

I suspect you'll find other solutions pretty soon. I'm still holding my breath for a solution with shafts {1..21}. :pray: Perhaps the original source was referring to that being unique. Or it has been proved utterly wrong with a brute force search like this and thus has disappeared from the googling range over these years. :rambo:

To confess, I don't have the solution with me all this time. :bigoops:

(It was on a corrupted old hard drive which I still haven't found time to recover. But I definitely know a solution exists, which might or might not be the one Richard found first. From vague memory it doesn't look like it so I guess there are probably more. Luckily Richard has found at least one solution to bail me out, or I would have to spend a lot of time digging it from my corrupted drive or some old archives. :salute:)

Also with that Richard has become the official winner this time (well he is no matter what). So whenever you like you could post another brainteaser/riddle. Hopefully it won't be a cpu-teaser (or more exact a cpu-workout) like mine. :oops:
Author:  Glyn [ Sun Jun 01, 2008 3:00 pm ]
Post subject:  Re: Brainteaser thread
Well done Richard. :applause: and thanks Matt for setting it. :thumbs:

It has forced me into having a crack at programming again, so not an entirely fruitless exercise for me.

As regards the {1..21} set this may be within the possible range of a manual calculation at least for the early placements. e.g 1 is either on the shortest rod or has 21 as its only neighbour.

Edit. {1..21} is manually checkable and has no solution. Failure to place 7 removes the last option.
Author:  rcbroughton [ Sun Jun 01, 2008 4:07 pm ]
Post subject:  Re: Brainteaser thread
Ok - a nice bit of gentle arithmetic then . . .

Please fill in the missing digits in this sum, similar to the famous Feynman Long Division:

Attachment:
equation.png
equation.png [ 4.2 KiB | Viewed 16764 times ]
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