Solving with colors

AzRunner · Posted: Wed Jul 19, 2006 1:27 am Post subject: Solving with colors

I'm having a problem understanding how colors are used when the candidates are not the same in a given row, column or grid. I have a sudoku puzzle that illustrates the issue I'm trying to understand, but, first, I can't seem to copy and paste it to this forum (or to any document, other than to save the image to a file on my computer).

So, first I need help on copying and pasting a partially solved puzzle from Simple Sudoku to this forum and then I can move on to my next question.

Thanks for your patience.

Dave · Posted: Sun Jul 23, 2006 11:55 pm Post subject: Copy and paste

Just hit Edit, then Copy while Simple Sudoku is open. Then when in the post creation (or reply) box, hit Edit, Paste.

AzRunner · Posted: Mon Jul 24, 2006 5:39 pm Post subject:

Well that was easy enough. I don't know what I was doing wrong the other day.

Anyway, I am having problems understanding the logic to eliminate candidates when the other candidate changes. The example below focuses on candidate 7.

In this puzzle:
Row 2 column 5: 47 -- Blue,
Row 2 column 8: 47 -- Green,
Row 3 column 7: 17 -- Blue,
Row 4 column 7: 17 -- Green.

A second chain can be set up with amber and pink as follows:
Row 3, column 4: 57 -- Pink,
Row 4, column 3: 37 -- Pink,
Row 5, column 4: 37 -- Amber,
Row 5, column 8: 37 -- Pink,
Row 6, column 3: 37 -- Amber,
Row 6, column 5: 37 -- Pink.

So, based on this, how do you go about eliminating candidates?

Thanks.

*--------------------------------------------------*
| 7 6 4 | 13 8 2 | 9 13 5 |
| 5 3 1 | 6 47 9 | 2 47 8 |
| 2 9 8 | 57 457 13 | 17 6 34 |
|----------------+----------------+----------------|
| 6 8 37 | 9 2 5 | 17 147 34 |
| 4 5 9 | 37 1 6 | 8 37 2 |
| 1 2 37 | 4 37 8 | 5 9 6 |
|----------------+----------------+----------------|
| 9 4 2 | 15 35 13 | 6 8 7 |
| 3 1 5 | 8 6 7 | 4 2 9 |
| 8 7 6 | 2 9 4 | 3 5 1 |
*--------------------------------------------------*

Ruud · Site Admin

There are no single digit methods that work for this grid.

It can be solved with an XY-Wing

Steve · Posted: Tue Jul 25, 2006 7:15 pm Post subject: Colours

AzRunner

Perhaps this short argument will help.

You will see that pink and blue share box 2 (r3c4 and r2c5). On the other hand pink and green share box 6 (r5c8 and r4c7).

Since one of green and blue stands for “contains 7” it follows that pink stands for “does not contain 7” and, as a result, amber stands for “contains 7.”

Entering and eliminating 7 according to this recipe finishes the puzzle at once.

Steve

AzRunner · Posted: Wed Jul 26, 2006 6:14 pm Post subject:

Steve,

Thanks. I think that does it for me. I have been working on puzzles that require multi-colors and then going back and reading the various threads that discuss multi-color solutions and I think it is finally starting to sink in. Thanks for your insight.

Norm