Solving strategy

Advanced methods and approaches for solving Sudoku puzzles

Solving strategy

Postby 01allenh » Mon Jun 04, 2007 8:45 am

When you first start a sudoku is it best to fill in every single candidate for each square and then search for x-wings etc, or should you look for some obvious ones first? If it is best to fill in every candidate is there anyway this could be speeded up as it takes me ages?
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Postby wapati » Mon Jun 04, 2007 9:51 am

I look at the puzzle and see what digits are most represented, and work on those.

I then usually pick the box with the most givens and check line versus box versus line.
I also check lines with many candidates and use line versus box and line versus line.

I often spot x-wings, and skyscrapers before I write in candidates. (I mark the cells with "x#", that cannot have that digit based on the x-wing.)

It is many steps later that I fill in candidates, and even then
I then usually fill in the cells with only 2 candidates and look for URs, locked pairs etc. before going to the cells with 3 candidates. At this point I look for URs and locked sets and x-wings and skyscrapers and xy-wings.

If I fill in a cell at any point I may go back to looking for singles etc.....

Ocean produced a puzzle where the first usefull step was a Swordfish. That is a tedious puzzle and is the only time that I have done all the candidates as a "first" step.

Hope this helps, and bear in mind it is just what I do, it may not be the best way!
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