... 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

... 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 |
+--------------+--------------+--------------+