OK, Sudoku mavens....

[SteveDallas]

Originally Posted by monster

third row eighth column is 7

...because it can either be 6 or 7, if it's 6 then r3c3 is 5, r3c6 is 8, r3c4 is 1, r1c4 is 4, r1 c8 is 9 which leaves no possibility for r7c8 (6 or 9)

Very clever! I often just throw up my hands at this point.. it's too close to guessing. But my experience is once you're at this point, you usually only have to figure out one number and the rest of it will fall apart.

The original numbers are supposed to be bold. The difference doesn't show much though. Here is the original:

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

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

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

FYI this is from Numberz, a PalmOS Sudoku application. It is rated as "insane"--I usually do Expert, but they are right next to each other and I apparently clicked the wrong button this time!