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October 6, 2006 Daily Puzzle and Contradictions

 
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Paladin



Joined: 10 Feb 2006
Posts: 15
PostPosted: Tue Oct 17, 2006 6:04 pm    Post subject: October 6, 2006 Daily Puzzle and Contradictions Reply with quote
Code:

+------------------------+---------------------------+-------------------------------+
|                        |                           |                               |
|     7      8      1    |  2,6,9       5      2,9   |      2,6        4         3   |
|                        |                           |                               | 
|     5      2      3    |      4     6,7        8   |      6,9      1,9   1,6,7,9   |
|                        |                           |                               |
|     4      9      6    |      1       3      2.7   |        5        8       2,7   |
+------------------------+---------------------------+-------------------------------+ 
|                        |                           |                               |
|     1      3      9    |  5,6,7     6,7        4   |        8        2       5,6   |   
|                        |                           |                               |
|     8      7      5    |    6,9       2        1   |    3,6,9      3,9         4   | 
|                        |                           |                               |
|     2      6      4    |  3,5,9       8    3,5,9   |        1        7       5,9   |
+------------------------+---------------------------+-------------------------------+
|                        |                           |                               |
|     9      5      8    |    2,3       4        6   |        7      1,3       1,2   |
|                        |                           |                               |
|     6      4    2,7    |      8       1    2,3,7   |    2,3,9        5       2.9   | 
|                        |                           |                               |
|     3      1    2,7    |  2,5,7       9    2,5,7   |        4        6         8   |
+------------------------+---------------------------+-------------------------------+   

This is the October 6th, 2006 Daily Sudoku puzzle.

After reducing the puzzle to the above positions, I was unable to proceed.  As I studied the puzzle, I believe that I discovered a contradiction which indicated that r6c9 must equal 5 (the contradiction was that if r6c9 was set at 9, then both r7c8 and r5c8 would equal 3). The “chains” for this contradiction were:

r6c9 ==> r8c9 ==> r7c9 ==> r7c8;

r6c9 ==> r5c8

Was this the most, or only, “logical” solution technique?

Thank you very much for your responses.

Paladin
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Angel



Joined: 26 Mar 2006
Posts: 31
PostPosted: Tue Oct 17, 2006 6:44 pm    Post subject: Reply with quote
There is an x-wing at r2c5, r2c9, r4c5, r4c9. This excludes 6 as a candidate for r2c7.
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