## Sudoku #12

Category: Sudoku
Sat, 02 Jul 2005, 10:01

In #10 and #11 I discussed some basic and advanced Sudoku solving techniques. Here is the second advanced technique. Unlike the previous one, the situation described here isn't quite as easy to spot. And you might not be able to eliminate quite as many possibilities as before. But any progress is still progress, so this technique is still worth knowing.

In this technique, look in any group (row, column, or square) for two possibilities (say, x and y) that occur in only two cells. Since these two possibilities must occur in either of these two cells, all other possibilities other than x and y can be eliminated from those two cells.

As with the previous advanced techique, this can also be extended to three possibilities occuring only in three cells of a group. But this situation rarely crops up.

Next time, I'll have a short discussion on the number 13. I'll get to the final advanced technique with puzzle #14.

Hans

 3 5 7 2
 2 7 8
 6
 2 9 1
 9 2
 4 2 8
 6
 4 1 9
 7 2 1 5