genina.com: Forum

This message was edited 1 time. Last update was at 16 Mar 2017 17:55:45

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 ?

you cannot exclude 5 only because it may be in a different cell. a correct solution is probably 2 up and 5 down. so, your approach cannot work and the sudoku may be solvable.

This message was edited 1 time. Last update was at 31 Mar 2017 00:28:57

These puzzles all have unique solutions. If you come to a final point like this then you made an error elsewhere in the puzzle... look for it (it's there) and undo until it's undone, then re-work the puzzle.

This puzzle has a single solution. I've just solved it by pencil, in the order listed below. Compare to find your error.

761 429 358
249 385 176
358 761 294

473 812 965
682 594 713
195 637 842

916 253 487
524 178 639
837 946 521

As I said before, you've made an error elsewhere. Go back and find your error before continuing to solve the puzzle incorrectly

This message was edited 1 time. Last update was at 1 Apr 2017 21:17:03

So I see what your question is.... but both instances you're questioning (the 7/4 and 9/1) are part of the given values. Thus, they're not interchangeable. Thus, there's only one, unique solution. It's not valid to interchange initial conditions.

You didn't make an error, you simply interpreted the initial conditions and solution incorrectly