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"the World's hardest logic/number puzzles"
http://www.calcudoku.org/forum/viewtopic.php?f=24&t=463
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Author:  main  [ Fri Aug 09, 2013 11:33 am ]
Post subject:  Re: "the World's hardest logic/number puzzles"

This is how I discovered your website, through the duplicate post you published on conceptis puzzles from July 25th.
I've been glad I found calcudoku.org ever since. Great way to burn some free time!

Author:  pnm  [ Fri Aug 09, 2013 11:38 am ]
Post subject:  Re: "the World's hardest logic/number puzzles"

main wrote:
This is how I discovered your website, through the duplicate post you published on conceptis puzzles from July 25th.
I've been glad I found calcudoku.org ever since. Great way to burn some free time!

Good to hear, thanks :-)

It also got copied to "gizmodo":
http://gizmodo.com/can-you-solve-the-10 ... 1064112665

Patrick

Author:  nicow  [ Fri Aug 09, 2013 3:28 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

Crazydad nr8 is not difficult. After applying simple logic, this puzzles is solved applying Ariadne's Threat in order to eliminate faulty candidates.
And more: the first 3 (!) numbers are quite simple to find.
So nr8 is only of medium difficulty.

I agree with CLM that it's not clear wether a puzzle is more difficult than an other one or not. Because at first there has to be consent to the measuring method.

My system solves the 21-12-2012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree.

As Dutch men say: "Het is de kift!" Ha ha.

Author:  pnm  [ Sun Aug 11, 2013 9:16 am ]
Post subject:  Re: "the World's hardest logic/number puzzles"

nicow wrote:
Crazydad nr8 is not difficult. After applying simple logic, this puzzles is solved applying Ariadne's Threat in order to eliminate faulty candidates.
And more: the first 3 (!) numbers are quite simple to find

I never knew that "Ariadne's threat" meant guessing & backtracking...
(shouldn't it be "thread" ?)

nicow wrote:
My system solves the 21-12-2012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree

There must be some strategies that can reduce this.

For example, my solver works with linear equations of up to 3 unknowns, which can of course be extended to 4, etc.

nicow wrote:
As Dutch men say: "Het is de kift!" Ha ha.


Ik denk het :-)

Author:  nicow  [ Sun Aug 11, 2013 7:11 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

pnm wrote:
I never knew that "Ariadne's threat" meant guessing & backtracking...
(shouldn't it be "thread" ?)

Ariadne's thread (indeed with a 'd'), is trying a candidate, and if the result is a faulty solution, this candidate is faulty. Trying all candidates is elaborate, but for a computer that doesn't matter. It is an easy way to clean up all candidates, and many times a good solution is found in the meantime(!).

pmn wrote:
nicow wrote:
My system solves the 21-12-2012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree

There must be some strategies that can reduce this.

For example, my solver works with linear equations of up to 3 unknowns, which can of course be extended to 4, etc.

Mine does the same, but in an other way, and up to 8 unknowns; this level can be set; 4 happens to be fast, but 6 is more secure in my solver.

Of course there can be more strategies implemented. But I search for an optimum: the easy puzzles (and all up to 8x8) are solved within a second or few seconds, so why building in extra logic?

But I am building in Row/block-interaction now for the larger puzzles. I'm curious...

Author:  pnm  [ Sun Aug 11, 2013 8:02 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

nicow wrote:
But I am building in Row/block-interaction now for the larger puzzles. I'm curious...

What do you mean by that?
(maybe that's already in my solver, maybe not..)

Patrick

Author:  nicow  [ Mon Aug 12, 2013 11:49 am ]
Post subject:  Re: "the World's hardest logic/number puzzles"

pnm wrote:
nicow wrote:
But I am building in Row/block-interaction now for the larger puzzles. I'm curious...

What do you mean by that?
(maybe that's already in my solver, maybe not..)

Patrick

In today's sudoku, candidate 3 in A3 is to be wiped out bij column/block interaction.
Here is how: H8=3 so B8 and A8 cannot be a 3.
B6=3 so B8 cannot be a 3
So, in block 7 value 3 only occurs in row A (A7 and A9)
That is why A3 cannot be a 3: in the intersection of row A and block 7 , the value 3 only exists.

(By turning the puzzle 90°, column/block is the same as row/block)

(edited)

Author:  pnm  [ Mon Aug 12, 2013 6:49 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

Interesting, thanks, I'll have to check if I'm already doing this.

(thread is going a bit off-topic..)

nicow wrote:
In today's sudoku, candidate 3 in A3 is to be wiped out bij column/block interaction.
Here is how: H8=3 so B8 and A8 cannot be a 3.
B7=3 so B8 cannot be a 3


You mean B6=3 so B9 cannot be a 3?

Author:  danaburns  [ Fri Aug 16, 2013 8:05 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

Is the link in a bad location for anyone else?
I have a hard time avoiding it when using the input popup thingie.
This is only an issue when I use a small screen device such as a phone.

Author:  pnm  [ Fri Aug 16, 2013 10:38 pm ]
Post subject:  Re: "the World's hardest logic/number puzzles"

danaburns wrote:
Is the link in a bad location for anyone else?
I have a hard time avoiding it when using the input popup thingie.
This is only an issue when I use a small screen device such as a phone.

Thanks for letting me know, I'll check this, and maybe
remove the link for small devices.

Patrick

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