A following grid has 2 solutions (swap the 5's and 2's) and therefore is not a valid one.
...5.2...
.........
.........
...2.5...
.........
.........
.........
.........
.........
These types of grid appear frequently in genina sudokus.
When I find the following combination, I exclude 5 from the possibilities at the case marked "?"
...5.2...
.........
.........
...2.?...
.........
.........
.........
.........
.........
As a result, I end-up with unsolvable sudokus. Could these invalid grids be excluded ?
|
