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 Difficult Sudoku 
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Posted on: Sun Jul 28, 2024 12:26 pm




Posts: 23
Joined: Tue Mar 14, 2017 12:46 am
Post Difficult Sudoku
I think that today-2024-07-28 Medium Sudoku is more difficult than average. It will be interest to know what Medium Sudoku was solved minimum times in the past.


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Posted on: Tue Jul 30, 2024 11:02 am




Posts: 89
Joined: Fri May 13, 2011 9:37 am
Post Re: Difficult Sudoku
Every solver maker has his own method of measuring the difficulty level. With heuristics.

The perception of difficulty differs between the computer and humans.
A computer uses a method finds figures, uses another method and finds more figures.

Bur for a human the difficulty may vary on how many figures are found by a certain method.

Only the basic methods are used in this site. Hidden singles, hidden pairs, naked pairs.
But not more complex methods as hidden triplets or swordfish or coloring.


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Posted on: Tue Jul 30, 2024 11:38 am




Posts: 994
Location: Ukraine
Joined: Tue Mar 01, 2016 10:03 pm
Post Re: Difficult Sudoku
nicow wrote:
Every solver maker has his own method of measuring the difficulty level. With heuristics.

The perception of difficulty differs between the computer and humans.
A computer uses a method finds figures, uses another method and finds more figures.

Bur for a human the difficulty may vary on how many figures are found by a certain method.

Only the basic methods are used in this site. Hidden singles, hidden pairs, naked pairs.
But not more complex methods as hidden triplets or swordfish or coloring.


You’ve used a lot of terminology that I am not familiar with. Can you explain these terms, please?


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Posted on: Tue Jul 30, 2024 1:45 pm




Posts: 193
Location: Canada
Joined: Thu Aug 04, 2011 7:40 pm
Post Re: Difficult Sudoku
paulv66 wrote:
You’ve used a lot of terminology that I am not familiar with. Can you explain these terms, please?


This is the "gold" website for Sudoku's, all those terms plus many more are described.


https://www.sudokuwiki.org/sudoku.htm


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Posted on: Wed Jul 31, 2024 3:17 pm




Posts: 89
Joined: Fri May 13, 2011 9:37 am
Post Re: Difficult Sudoku
frederick wrote:
paulv66 wrote:
You’ve used a lot of terminology that I am not familiar with. Can you explain these terms, please?


This is the "gold" website for Sudoku's, all those terms plus many more are described.


https://www.sudokuwiki.org/sudoku.htm

That is a good site for studing sodoku strategies!

We humans like these strategies as they yield a feeling of certainty.
Astonishingly, a very simple method like 'removing false candidates', is not approved a proper method. For humans this method is elaborate, but for a computer it is very simpel.
And methods like colouring, is for a computer elaborate, and is easily replaced by removing false candidates.

Thus a solver can be simple. A) use simple logic (easy ones are solved), B) remove false candidates (difficult ones are solved), C) use brute force (all, inclusive 'not solvable' ones) are solved.

In real life you can solve any problem this way.


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Posted on: Wed Jul 31, 2024 5:08 pm




Posts: 193
Location: Canada
Joined: Thu Aug 04, 2011 7:40 pm
Post Re: Difficult Sudoku
nicow wrote:
That is a good site for studing sodoku strategies!


Back when I was a sudoku fanatic I spend hours studying the strategies on that site. If you succeed in learning them all you will be a sudoku grandmaster:)


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Posted on: Sun Aug 11, 2024 7:05 am




Posts: 8
Joined: Sun May 01, 2022 9:43 pm
Post Re: Difficult Sudoku
I wonder how the difficulty rating of puzzles is determined on this site.
I would tend to look at which techniques are required to solve the problem.
In the cited example (Medium Sudoku for 20240728) the puzzle can be solved using only the two most basic techniques:

1. When the value for a given square has been determined, remove the like valued candidates from the other points in the same row, column or box.
2. Naked singles: When a value occurs in only one point of a row, column or box, then assign that value to the point.

So I wonder why this puzzle has been assigned a medium level of difficulty and what makes it harder then the sudoku problems in the easy section.


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Posted on: Sun Aug 11, 2024 11:33 am




Posts: 89
Joined: Fri May 13, 2011 9:37 am
Post Re: Difficult Sudoku
crabmouse wrote:
I wonder how the difficulty rating of puzzles is determined on this site.
I would tend to look at which techniques are required to solve the problem.
In the cited example (Medium Sudoku for 20240728) the puzzle can be solved using only the two most basic techniques:

1. When the value for a given square has been determined, remove the like valued candidates from the other points in the same row, column or box.
2. Naked singles: When a value occurs in only one point of a row, column or box, then assign that value to the point.

So I wonder why this puzzle has been assigned a medium level of difficulty and what makes it harder then the sudoku problems in the easy section.

It is even simpler, Crabmouse!

Only point 2. and only column and row will do!

So it is really an easy sudoku.


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Posted on: Sun Aug 11, 2024 1:15 pm




Posts: 3371
Joined: Thu May 12, 2011 11:58 pm
Post Re: Difficult Sudoku
crabmouse wrote:
So I wonder why this puzzle has been assigned a medium level of difficulty and what makes it harder then the sudoku problems in the easy section.


For the Sudoku puzzles I'm using someone else's software (I never really liked Sudoku's to be honest.. [blush] )

(it's this one: http://www.lemo.dk/sudoku/)


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