Templates and Quad-Exclusions

daj95376 · Posted: Sun Feb 26, 2006 3:25 pm Post subject: Templates and Quad-Exclusions

Is there anyone, whose Sudoku generator supports templates, is willing to: (1) make a (hopefully) modest change to their source, (2) generate (say) 10,000 puzzles, and (3) report back on the difficulty distribution of the puzzles?

I would like to use the following template (sorry if it's not in a standard format) ... AND ... have the digits '1234' disabled as candidates in the clue squares. (I hope this hasn't already been done!)

Since my additional constraint may actually result in no solution being possible, you will need to test for this possibility. If there is a problem, then please reduce my constraint to the digits '123' and try again.

Ruud · Site Admin

Hi,

If you want to have puzzles with a unique solution, you need clues for at least 8 of the 9 digits. Anything less would allow exchanging 2 digits completely, leading to multiple solutions.

Ruud.
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Cristian2006 · Posted: Sat Mar 04, 2006 5:22 am Post subject:

daj95376 · Posted: Sun Mar 05, 2006 7:01 pm Post subject:

I understand why only one missing value is allowed when supplying clues. However, I didn't realize the scope of this constraint until I generated the following filled grid and manually started removing values.

Ruud · Site Admin

Yes,

2 empty rows or 2 empty columns will also cause multiple solutions.

Another way is not to place a clue in an unavoidable set.

Ruud.

fermat · Posted: Thu Mar 09, 2006 5:33 am Post subject:

daj95376 · Posted: Thu Mar 09, 2006 6:57 am Post subject:

If you look even closer, moderate1.ss has two empty rows AND two empty columns.

However, every digit is present in the 22 clue cells, so my original message still has its fallacies. No matter, I'm here to learn and have fun.

For those who don't have access to Simple Solver, here's moderate1.ss. I hope posting this doesn't offend angusj!

vidarino · Posted: Thu Mar 09, 2006 9:38 am Post subject:

Puzzles can have several empty rows and columns, but never more than one empty row in each "band" (horizontal 9x3 block) and never more than one empty column in each "stack" (vertical 9x3).

If a puzzle did have two empty rows in one band, you could switch the rows and still have a valid solution. (You won't get to any of the solutions without guessing, though, since the puzzle would be ambiguous.)