Basic Sudoku questions...

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Basic Sudoku questions...

Postby msmmsm » Fri Feb 13, 2009 5:38 pm

I have moved up in difficulty and now have to write multiple entries into a box to show all the possible candidates to help me. I find simple colouring(and many others) very hard to work out without putting possible candidates in each box, is this cheating?

When I get stuck on a particular puzzle I give it my best shot then go online and look at the different stategies and try and apple them to my puzzle, is this also classed as cheating?

Does the average Sudoku player work all these strategies out themselves( from x-wings to evil stategies) or do you learn them from the web then apple them?

Thank you for any feedback

Mark
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Re: Basic Sudoku questions...

Postby tarek » Fri Feb 13, 2009 10:04 pm

msmmsm wrote:very hard to work out without putting possible candidates in each box, is this cheating?
Hi Mark & welcome to the forum,

The possible candidates are usually referred to as "Pencilmarks" when displayed on a sudoku grid (written or typed).

AFAIK there is no standard regarding what is cheating or not in sudoku solving.

Most palyers however try to advance towards solution avoiding guessing or brute force solving.

The use of Pencilmarks is common when using advanced techniques (The term advanced is VERY subjective).

An advocate of solving without pencilmarks when possible is RW. follow this link http://forum.enjoysudoku.com/viewtopic.php?t=3640

You might want to refresh your sudoku terminology by visiting Sudopedia

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Postby msmmsm » Sat Feb 14, 2009 7:19 pm

Thank you for your reply, I read the thread by RW and found it very interesting, I have not been using pencilmarks for a long time, I find it easier and a lot less clutter when viewing the grid. I have completed the first 100 extreme sudokus by Wayne Gould in this way then lost my book, so moved to a phone application which surprised me with new stategies (simple colouring and hidden unique rectangles) which I find difficult atm however I will stick at it and try to not use pencilmarks.

I never guess a solution for a sudoku puzzle and don't understand why anyone would want to.

Mark
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Postby DonM » Sun Feb 15, 2009 2:10 am

msmmsm wrote:I have completed the first 100 extreme sudokus by Wayne Gould in this way then lost my book, so moved to a phone application which surprised me with new stategies (simple colouring and hidden unique rectangles) which I find difficult atm however I will stick at it and try to not use pencilmarks.Mark


I'm a little confused by your last sentence. RW does use strategies without pencil marks that he feels replace methods such as simple colouring, but unless I'm missing something, the actual use of methods such as simple colouring and hidden unique rectangles requires the use of pencil marks.
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Postby msmmsm » Sun Feb 15, 2009 7:37 pm

Hidden unique rectangles I would say do not require pencil marks, in fact I would say no strategy requires pencil marks, just a very good memory/system to find and work them out. However this makes the puzzle a lot lot harder and may take the fun out of it, more rewarding if you got it though:D

I will give it a few weeks seeing if I can do it, but may resort to pencil marks, lol
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Postby eleven » Sun Feb 15, 2009 10:01 pm

Probably there are 2 meanings of hidden unique rectangles. For non-pm-solvers this would be one to place 2 in r4c3:
Code: Select all
 # # 3
 4 5 6
 7 8 9
-------
 # # . |
 3 4 5 |
 . . . | 1 2
-------
 . . 1

Not both 1 and 2 can be in r4c12, so one of them must be elsewhere in the box. It is "hidden", when you stare at (a lot of) pencilmarks.

However others (like JSudoku) call a hidden UR one, where you can eliminate a UR candidate because of strong links (also called UR type 6 i think).
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Postby msmmsm » Sun Feb 15, 2009 11:43 pm

Thank you for that example, I have played Sudoku for a while and I am still learning all the proper names for the various Strategies. Will browse this forum for some tips when I get time:)

This is exactly the type of Stategy that I am trying to "see", quite hard for me, even if I use pencil marks.

Mark
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Postby StrmCkr » Tue Feb 17, 2009 8:52 am

the hint to spot them with out pms

look for x-wings in same band/stack
:)
that locks 1 digit automatically for them and highlights which cells could be the hidden/Urs

using the example above:
all #'s are an x wing on digit 1.
Some do, some teach, the rest look it up.
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