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keith
Joined: 19 Sep 2005 Posts: 3260 Location: near Detroit, Michigan, USA

Posted: Fri Mar 14, 2008 6:41 am Post subject: Sudoku template for pencil & paper solvers 


All,
I have evolved my grid to this:
http://www.mediafire.com/?p9jxjggiwom
I have found it very useful to solve those very difficult puzzles.
Top left: The sudoku grid. I usually write the initial clues with a color pen. OR: If you are in the final stages of a puzzle, write in only the candidates of the unsolved cells. The solved cells are not relevant.
Bottom left:
123
456
789
I always write this in the margin of any puzzle I do, then I black out the number when it is solved in all boxes. Very useful in the final stages of solving a puzzle.
Solved / Unsolved
At some point, you give up on basics and decide you need to do coloring or look for chains. Fill in the circles for boxes in which the candidate is solved or unsolved. This is a great way to decide on candidates for coloring or chains. When I get to a crunch point, I fill in the diagram for the unsolved. I do not keep track of the solved as I go, but you might want to do so.
Right half:
These are stencils for coloring or looking at patterns. Pick a candidate. In one of the stencils, black out each dot where that candidate occurs.
Your empty rectangles, Xwings, skyscrapers, etc., will be very obvious!
I have found this template very useful to solve puzzles that, a few days ago, I would have gone to the computer to solve. I am now thinking about how to use the coloring stencils for Medusa coloring or XYchains.
Best wishes,
Keith 

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keith
Joined: 19 Sep 2005 Posts: 3260 Location: near Detroit, Michigan, USA

Posted: Fri Mar 14, 2008 8:19 pm Post subject: An example 


Here is an example:
http://www.mediafire.com/?3g1cdyzyq2q
It is the Free Press puzzle of 14 March, 2008:
Code:  Puzzle: FP031408
++++
 9 1 .  . . 5  8 . 6 
 . . 8  . 6 .  . 5 . 
 . . .  . . 1  . . . 
++++
 . . .  1 7 .  . . . 
 . 7 5  6 . 9  4 3 . 
 . . .  . 2 3  . . . 
++++
 . . .  3 . .  . . . 
 . 3 .  . 1 .  5 . . 
 1 . 6  4 . .  . 9 7 
++++ 
http://www.dailysudoku.com/sudoku/forums/viewtopic.php?t=2410
The original clues are copied in red. I got to this point, having solved 1, 3, 5, and 9. Now count the unsolved values by filling in the circles.
7 has two unsolved values. Check that there are 4 candidates that lie on a rectangle.
Put the patterns for 2, 4, 6, and 8 on the coloring grids. Draw lines for the strong links.
I could see nothing for 6.
4 has a number of skyscrapers, etc. It turns out that the cells marked by x cannot be 4, and this solves the puzzle.
There is at least one coloring elimination for 2, but it is not needed.
Keith 

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