A few tips on applying & spotting adv. techniques please

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A few tips on applying & spotting adv. techniques please

Postby PDN » Wed Jul 03, 2013 8:53 pm

Hi,

I've been using Andrew Stuart's amazing online solver:

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

I've also been studying the various techniques.

I've been applying the techniques in the order his solver does,
but I am wondering if there are tips to spot when to try
which technique.

A couple I've thought of (please comment if I'm off):

* If there are many cells with only two candidates, try
an XY-wing, or simple chain;

* If there is only one or two solutions of a given digit
(ie, only two 6s appear in the solution thus far), its
probably not time to draw chains on 6 yet...too many
units with more than 2 appearances of 6.

Anyway -- tips like this, which will help me apply the
techniques...

One last question -- is it true some puzzles will take
dozens of hours to solve? It certainly looks that way
to me! (I am doing "Inferno" level puzzles from a Mac
program named Amnesiak.)

Thanks!

--Prahas
PDN
 
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Re: A few tips on applying & spotting adv. techniques please

Postby JC Van Hay » Thu Jul 04, 2013 8:27 am

Have a look here
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Re: A few tips on applying & spotting adv. techniques please

Postby Serg » Thu Jul 04, 2013 11:02 am

Hi, PDN!
Maybe I missed something in your question ...
Andrew Stuart's Sudoku Solver uses rather natural approach to the choice of proper solving method. First it tries to apply simplest method by systematic checking rows/columns/boxes in turn. When it hasn't managed to apply the method, it tries to use more complicated method. Andrew Stuart has his own (rather common) order of methods by their complexity. You can use this order or choose your own order. (Some people, for example, says they found easier to catch XY-wing than hidden pairs, etc.)

Serg
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