Help with this puzzle

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Help with this puzzle

Postby eddydo » Sat Apr 15, 2006 1:51 am

Hello I was wondering if someone can help with this puzzle.
I am fairly new to Sudoku, and would like some help.

* 6 7 * 3 * 1 5 *
3 * * 7 * 5 * * 8
4 * * * * * * * 3



* 7 * * * * * 8 *
9 * * * * * * * 7
* 2 * * * * * 1 *



7 * * * * * * * 6
5 * * 4 * 3 * * 9
* 8 4 * 2 * 5 3 *

I hope I posted the puzzle so everyone understands it. I am not sure if it will show up as planned.

Thanks for the help:?:

eddydo
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Postby Hud » Sat Apr 15, 2006 2:31 am

About the only suggestion I would have would be to use pencilmarks when you get as far as you can with logic. I guess I should have tried it sans pencilmarks; maybe tomorrow.
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Postby Hud » Sat Apr 15, 2006 3:14 am

Without pencilmarks the puzzle is still pretty straight forward. A key late in solving it might be that 1,2,8 must go horizontally in the middle box, not necessarilly in that sequence. That places candidates elsewhere
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Re: Help with this puzzle

Postby Cec » Sat Apr 15, 2006 3:46 am

Hi eddydo and welcome to the Forum.

You say you are new to Sudoku. The possible numbers for unsolved cells are known as "candidates" or "pencilmarks" and your "Pencilmark" grid would look like this:
Code: Select all
 *-----------------------------------------------------------------------------*
 | 28      6       7       | 289     3       2489    | 1       5       24      |
 | 3       19      129     | 7       1469    5       | 2469    2469    8       |
 | 4       159     12589   | 12689   1689    12689   | 2679    2679    3       |
 |-------------------------+-------------------------+-------------------------|
 | 16      7       1356    | 123569  14569   12469   | 23469   8       245     |
 | 9       1345    13568   | 123568  14568   12468   | 2346    246     7       |
 | 68      2       3568    | 35689   456789  46789   | 3469    1       45      |
 |-------------------------+-------------------------+-------------------------|
 | 7       139     1239    | 1589    1589    189     | 248     24      6       |
 | 5       1       126     | 4       1678    3       | 278     27      9       |
 | 16      8       4       | 169     2       1679    | 5       3       1       |
 *-----------------------------------------------------------------------------*

Each row, column and "Box" (these are the nine 3X3 boxes within the puzzle grid) must contain each of the digits 1 to 9. As you already have digits 3,4,5 and 9 placed in row8 (r8) and digits 2,6,7 and 8 placed in column2 (c2) then this leaves only one possible number (known as a "naked single") to fill cell r8c2 - it can only be digit 1. By excluding the other candidate 1's in c2 this leaves digit 9 as the only number to fill cell r2c2. In row9 candidate 1 is the only number that can fill cell r9c9 - this then enables all other candidate1's being excluded from row9 leaving digit 6 to fill cell r9c1.
Continuing with this procedure can lead to solving this puzzle. If you need more help then just ask - there is usually someone available to help you

You can read up on the procedure for posting puzzles and terminology by clicking on HERE. The following links are also popular for learning the "basic" solving techniques:
http://www.angusj.com/sudoku/hints.php
http://www.simes.clara.co.uk/programs/sudokutechniques.htm

Good luck with your sudoku.

PS. Hud is correct that this puzzle is pretty straight forward without the need for pencilmarks but I decided to retain my above comments as additional help.

Cec
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