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BUG

BUG stands for Bi-Value Universal Grave

As of March 2010 this strategy has been deprecated. It is extremely rare considering the alternatives - and perhaps because my algorithm for finding it was too specific. I would like to document it however, since it is unusual Uniqueness strategy..

The principle behind BUG is the observation that any sudoku where all remaining cells contain just two candidates is fatally flawed. There would have been a last remaining cell with three candidates. The odd number that couldn't be paired with another cell would have to be the solution for that cell in order to prevent the bi-value 'Graveyard'.



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Comments Talk

Wednesday 24-Mar-2010

... by: Sean Forbes

Andrew, While I agree that a more astute player will more than likely identify and utilize some other solving technique before resorting to this one, I find this method very handy in real-time online competitions, especially if I've overlooked one of the more effective solving techniques up to the point when I can recognize the BUG pattern.

Thanks. Sean

Friday 19-Mar-2010

... by: Harmen Dijkstra

i have a sudoku with this strategy:

+--------------+--------------+--------------+
| 4 2 1 | 5 8 6 | 9 3 7 |
| 5 9 38 | 1 34 7 | 2 48 6 |
| 6 7 38 | 2 34 9 | 14 148 5 |
+--------------+--------------+--------------+
| 7 1 9 | 8 2 3 | 5 6 4 |
| 2 5 6 | 4 7 1 | 8 9 3 |
| 8 3 4 | 9 6 5 | 17 17 2 |
+--------------+--------------+--------------+
| 1 6 5 | 3 9 2 | 47 47 8 |
| 3 4 2 | 7 1 8 | 6 5 9 |
| 9 8 7 | 6 5 4 | 3 2 1 |
+--------------+--------------+--------------+

with this strategy, we will get this solution:

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

However, there are other solutions, for example:

+--------------+--------------+--------------+
| 4 2 1 | 5 8 6 | 9 3 7 |
| 5 9 8 | 1 3 7 | 2 4 6 |
| 6 7 3 | 2 4 9 | 1 8 5 |
+--------------+--------------+--------------+
| 7 1 9 | 8 2 3 | 5 6 4 |
| 2 5 6 | 4 7 1 | 8 9 3 |
| 8 3 4 | 9 6 5 | 7 1 2 |
+--------------+--------------+--------------+
| 1 6 5 | 3 9 2 | 4 7 8 |
| 3 4 2 | 7 1 8 | 6 5 9 |
| 9 8 7 | 6 5 4 | 3 2 1 |
+--------------+--------------+--------------+
Article created on 11-April-2008. Views: 40547
This page was last modified on 7-March-2010.
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Copyright Andrew Stuart @ Syndicated Puzzles Inc, 2011