The New Sudoku Players' Forum

[Pyrrhon]

You can't proof that there are least 2 solutions whenever you have a deadly pattern or 2 not-used digits. In the first case must in the second can the sudoku have none solution.

[Deano]

Try this site

JPF

It's an interesting little tool! However, after a few hundred attempts I've given up on it ever creating anything beyond easy puzzles. Am I missing something in the translation?

[tso]

Try this site

JPF

It's an interesting little tool! However, after a few hundred attempts I've given up on it ever creating anything beyond easy puzzles. Am I missing something in the translation?

No. I'm not absolutely *sure* that it won't create harder puzzles, but I haven't seen one. Most methods of creating puzzles will create far more easy ones than hard ones, regardless of how you define "easy" and "hard" -- but it may be that the method used on that page is even less likely or impossible to create harder ones. If -- and I'm guessing -- it creates puzzles by randomly adding digits to the template and then testing for solvability -- and if the sovablity test is a set of logical tactics instead of a brute force search, it will *only* return those that are solvable with those rules. Since it's a Japanese site that's been around for several years, the target would likely be less than x-wing level puzzles.

I've found it interesting that some templates entered in this applet will make puzzle very quickly -- the same template entered in Michael Kennett's program might run for many minutes without finding one. And yet another template might have the opposite results. Kennett's program will make puzzles of a much wider range of difficulty.

[claudiarabia]

Hi,

here is another heart-attack.

Code: Select all

. 9 5|6 . 7|3 2 .
2 . .|. 5 .|. . 4
. . 8|. . .|6 . .
------------------
. . 3|. 1 .|5 . .
1 . .|9 . 5|. . 8
. 4 .|. 3 .|. 6 .
------------------
. . 1|. . .|9 . .
. . .|5 . 3|. . .
. 8 .|. 4 .|. 5 .

double heart



Claudia

[m_b_metcalf]

Here's one with 4 little rectangles, easy but pretty.

Code: Select all

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


Regards,

Mike Metcalf

[tso]

Here's one with 4 little rectangles, easy but pretty.

Five of the same pattern, in increasing difficulty:

Code: Select all

+-------+-------+-------+
| . . . | . . . | . . . |
| . 3 8 | 5 . 9 | 4 6 . |
| . 9 . | 3 . 2 | . 5 . |
+-------+-------+-------+
| . 2 9 | 4 . 5 | 7 8 . |
| . . . | . . . | . . . |
| . 5 1 | 6 . 7 | 2 4 . |
+-------+-------+-------+
| . 1 . | 9 . 3 | . 2 . |
| . 7 5 | 8 . 4 | 1 3 . |
| . . . | . . . | . . . |
+-------+-------+-------+

+-------+-------+-------+
| . . . | . . . | . . . |
| . 6 1 | 4 . 9 | 7 2 . |
| . 5 . | 7 . 1 | . 8 . |
+-------+-------+-------+
| . 8 2 | 6 . 4 | 3 1 . |
| . . . | . . . | . . . |
| . 3 7 | 1 . 2 | 5 6 . |
+-------+-------+-------+
| . 2 . | 3 . 8 | . 7 . |
| . 9 4 | 2 . 6 | 1 3 . |
| . . . | . . . | . . . |
+-------+-------+-------+

+-------+-------+-------+
| . . . | . . . | . . . |
| . 9 3 | 6 . 8 | 5 4 . |
| . 4 . | 1 . 3 | . 8 . |
+-------+-------+-------+
| . 3 8 | 5 . 2 | 7 1 . |
| . . . | . . . | . . . |
| . 2 9 | 3 . 1 | 8 5 . |
+-------+-------+-------+
| . 5 . | 4 . 7 | . 6 . |
| . 7 6 | 2 . 5 | 9 3 . |
| . . . | . . . | . . . |
+-------+-------+-------+

+-------+-------+-------+
| . . . | . . . | . . . |
| . 2 5 | 4 . 7 | 1 9 . |
| . 8 . | 3 . 9 | . 2 . |
+-------+-------+-------+
| . 1 3 | 5 . 4 | 9 7 . |
| . . . | . . . | . . . |
| . 6 9 | 2 . 3 | 4 1 . |
+-------+-------+-------+
| . 5 . | 9 . 2 | . 4 . |
| . 4 7 | 6 . 5 | 3 8 . |
| . . . | . . . | . . . |
+-------+-------+-------+

+-------+-------+-------+
| . . . | . . . | . . . |
| . 3 8 | 4 . 9 | 2 6 . |
| . 4 . | 2 . 8 | . 1 . |
+-------+-------+-------+
| . 5 7 | 8 . 6 | 1 3 . |
| . . . | . . . | . . . |
| . 8 2 | 5 . 1 | 9 7 . |
+-------+-------+-------+
| . 9 . | 7 . 2 | . 5 . |
| . 2 5 | 1 . 3 | 6 8 . |
| . . . | . . . | . . . |
+-------+-------+-------+

[ravel]

Surprising hard puzzles. For the last one i needed a very long chain.

[m_b_metcalf]

Here's a band plus dot that I came up with:

Code: Select all

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


Regards,

Mike Metcalf

[JPF]

Nice,
Of course, you can do it dotless...

Code: Select all


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



JPF

[tso]

The slash patten is a nice one.

I went to Puzzle Laboratory and very quickly created several puzzles using this mask. Of course they were easy puzzles, as this applet -- as far as I know -- only creates puzzles that can be solved completely with singles. Then, I tried to use Michael Kennett's program, using the same mask:

Code: Select all

%
.......**
......***
.....***.
....***..
...***...
..***....
.***.....
***......
**.......

I let it run for about twenty minutes and it found nothing. Since Michael's program can find puzzles of all difficulty levels given other templates with the same number of clues -- in some cases finding hundreds or thousands a minute, this is baffling to a non-programmer layperson.

Why do you suppose this is?

[m_b_metcalf]

Then, I tried to useMichael Kennett's program, using the same mask:

[snip]

I let it run for about twenty minutes and it found nothing. Since Michael's program can find puzzles of all difficulty levels given other templates with the same number of clues -- in some cases finding hundreds or thousands a minute, this is baffling to a non-programmer layperson.

Why do you suppose this is?

I am similarly perplexed. I have two completely independent programs to generate puzzles from templates. One is based on a randomised brute force generator with a brute force solver, the other on a completely random generator with a logic solver. For the band plus dot, each requires only a few seconds to generate a valid puzzle. Without the dot, I have run each for an hour real time at 1.6GHz, equivalent to about 1 million attempts each, and neither gets a hit. What's so special about this template?

Regards,

Mike Metcalf

[Edit added years later: Now, thankfully, new versions are more successful.]

[claudiarabia]

Here's one with 4 little rectangles, easy but pretty.

Five of the same pattern, in increasing difficulty:

I like these edge-nontouching rectangles. Mostly they are pretty hard but tasty nuts to crack.

This day I tried to refine a previous puzzle of mine.

I came out with this:

Code: Select all

+-------+-------+-------+
| . . 9 | 1 . 2 | 7 . . |
| . 3 . | . 4 . | . 1 . |
| . . 2 | . . . | 6 . . |
+-------+-------+-------+
| . . . | 3 . 4 | . . . |
| . . . | . 8 . | . . . |
| . . . | 9 . 7 | . . . |
+-------+-------+-------+
| . . 5 | . . . | 2 . . |
| . 1 . | . 9 . | . 4 . |
| . . 7 | 6 . 5 | 9 . . |
+-------+-------+-------+
Simply loving hearts

Unfortunately this was not that simple in creation because despite restless trial I couldn't eliminate two naked pairs which make the sudoku bi-solutional. It's the notorious 4/77-thing. But because the two confused numbers shouldn't affect the solving that much and I consider this beautiful I hope you will forgive me.

Claudia

[ab]

I like the bar shape

here's one that needs locked candidates:

Code: Select all

 . . . | . . . | . 6 2
 . . . | . . . | 9 8 4
 . . . | . . 2 | 5 3 .
 ------+-------+------
 . . . | . 2 9 | 1 . .
 . . . | 6 4 7 | . . .
 . . 6 | 5 8 . | . . .
 ------+-------+------
 . 9 8 | 4 . . | . . .
 2 5 7 | . . . | . . .
 6 3 . | . . . | . . .



here's a slight variation on the pattern, but an easy puzzle:

Code: Select all

 . . . | . . . | . 9 5
 . . . | . . . | 3 6 1
 . . . | . . 2 | . 4 .
 ------+-------+------
 . . . | . 5 8 | 4 . .
 . . . | 1 7 4 | . . .
 . . 5 | 9 6 . | . . .
 ------+-------+------
 . 7 . | 6 . . | . . .
 2 8 3 | . . . | . . .
 1 4 . | . . . | . . .


and here's a real sudoku with your hearts Claudia:

Code: Select all

 . . 1 | 5 . 9 | 2 . .
 . 8 . | . 7 . | . 9 .
 . . 3 | . . . | 4 . .
 ------+-------+------
 . . . | 1 . 4 | . . .
 . . . | . 5 . | . . .
 . . . | 6 . 2 | . . .
 ------+-------+------
 . . 6 | . . . | 1 . .
 . 5 . | . 3 . | . 7 .
 . . 7 | 2 . 8 | 3 . .



[claudiarabia]

.... and here's a real sudoku with your hearts Claudia:...

Hi ab

Thank you very much. I knew, somebody of you will tackle the challenge.

With best wishes

Claudia

[ab]

here's a puzzle with the slash mask that needs xy wings:

Code: Select all

 . . . | . . . | . 4 9
 . . . | . . . | 8 5 1
 . . . | . . 8 | 7 6 .
 ------+-------+------
 . . . | . 3 1 | 2 . .
 . . . | 5 2 7 | . . .
 . . 5 | 4 9 . | . . .
 ------+-------+------
 . 9 4 | 3 . . | . . .
 5 2 1 | . . . | . . .
 6 8 . | . . . | . . .