The New Sudoku Players' Forum

[Ocean]

This is the C1-norm of one of the two known minimal sudokus with 35 clues:

Code: Select all

 *-----------*
 |123|45.|67.|
 |7..|3..|..4|
 |...|.6.|2..|
 |---+---+---|
 |312|...|78.|
 |87.|...|...|
 |..5|...|..2|
 |---+---+---|
 |68.|13.|4.9|
 |2.1|.4.|.6.|
 |.4.|.86|3..|
 *-----------*

I have not been able to solve it without using long forcing chains.
Maybe one of you experienced solvers could find the best/simplest solving strategy?

[vidarino]

Good job on finding that one!

Basic steps should take you here;

Code: Select all

 1     2     3     |  4     5     9     |  6     7     8   
 7     569   68    |  3     12    128   |  59    159   4   
 49    59    48    |  78    6     178   |  2     1359  135 
-------------------+--------------------+--------------------
 3     1     2     |  56    9     4     |  7     8     56   
 8     7     46    |  256   12    123   |  59    3459  356 
 49    69    5     |  68    7     38    |  1     34    2   
-------------------+--------------------+--------------------
 6     8     7     |  1     3     25    |  4     25    9   
 2     3     1     |  9     4     57    |  8     6     57   
 5     4     9     |  27    8     6     |  3     12    17   

My solver suggests;
R2C8-1-R9C8-2-R9C4-7-R3C4=7=R3C6=1=[R2C56]-1-R2C8
-> R2C8 <> 1

The rest of the steps are pretty basic (the most complex being a hidden pair).

Vidar

[Carcul]

Hi Ocean.

I have not been able to solve it without using long forcing chains.

That's strange, because this is a very easy puzzle:

Code: Select all

 *-----------------------------------------------------------*
 | 1     2     3     | 4     5     9     | 6     7     8     |
 | 7     569   68    | 3     12    128   | 59    159   4     |
 | 49    59    48    | 78    6     178   | 2     1359  135   |
 |-------------------+-------------------+-------------------|
 | 3     1     2     | 56    9     4     | 7     8     56    |
 | 8     7     46    | 256   12    123   | 59    3459  356   |
 | 49    69    5     | 68    7     38    | 1     34    2     |
 |-------------------+-------------------+-------------------|
 | 6     8     7     | 1     3     25    | 4     25    9     |
 | 2     3     1     | 9     4     57    | 8     6     57    |
 | 5     4     9     | 27    8     6     | 3     12    17    |
 *-----------------------------------------------------------*


[r2c3]-6-[r2c2|r2c7]-5,9-[r2c8]-1-[r9c8]-2-[r9c4]-7-[r3c4]-8-[r3c3]-4-[r5c3]-6-[r2c3],

which implies r2c3<>6 and that solve the puzzle.

My solver suggests;

With all respect, it would be very nice if, at least from time to time, the progammers out there decide to try to solve a puzzle such as this one by hand, instead of just keep posting the output of the solvers (sometimes very long outputs).

Regards, Carcul

[vidarino]

With all respect, it would be very nice if, at least from time to time, the progammers out there decide to try to solve a puzzle such as this one by hand, instead of just keep posting the output of the solvers (sometimes very long outputs).

Ah, you're just saying that because my chain was shorter than yours.

Just kidding.

I did actually solve it myself, using the Almost Unique Rectangle at R25C56, but the chain became rather long and unwieldy, and since Ocean asked for "the best/simplest solving strategy", I figured I should post my solver's chain instead, since it was much shorter.

When solving manually I have a real fetish for using AUR's, though. ;-)

[Ocean]

Thank you both! As you pointed out, there is only one 'hard' step. Without a proper tool, I don't know how to quickly find the best logic there.

Thank you for the chains!

[tarek]

I have to disagree on this Carcul....
I tried this by hand & oddly enough I spotted the Triple which is not needed & missed the double.......

The solver showed me the way, & I hope this is not long...

Code: Select all

*--------------------------------------------------------*
| 1     2     3    | 4     5     9    | 6     7     8    |
| 7     569   68   | 3    *12   *128  | 59    159   4    |
| 49    59    48   | 78    6    -178  | 2     1359  135  |
|------------------+------------------+------------------|
| 3     1     2    | 56    9     4    | 7     8     56   |
| 8     7     46   | 256  *12   *123  | 59    3459  356  |
| 49    69    5    | 68    7    ^38   | 1     34    2    |
|------------------+------------------+------------------|
| 6     8     7    | 1     3     25   | 4     25    9    |
| 2     3     1    | 9     4     57   | 8     6     57   |
| 5     4     9    | 27    8     6    | 3     12    17   |
*--------------------------------------------------------*
Candidates 38 form a Quantum cell as Candidates 12 in r2c5,r5c5,r2c6 & r5c6 form a unique quadrangle which leads to:
r3c6 Must only have 17 as valid Candidates (38 is a Naked Double in Column 6)
*--------------------------------------------------------*
| 1     2     3    | 4     5     9    | 6     7     8    |
| 7     569   68   | 3     12    128  | 59    159   4    |
| 49    59    48   | 78    6     17   | 2     1359  135  |
|------------------+------------------+------------------|
| 3     1     2    |*56    9     4    | 7     8    *56   |
| 8     7     46   |*256  ^12   ^123  | 59   -3459 *356  |
| 49    69    5    | 68    7     38   | 1     34    2    |
|------------------+------------------+------------------|
| 6     8     7    | 1     3     25   | 4     25    9    |
| 2     3     1    | 9     4     57   | 8     6     57   |
| 5     4     9    | 27    8     6    | 3     12    17   |
*--------------------------------------------------------*
Candidates 23 form a Quantum cell as Candidates 56 in r4c4,r4c9,r5c4 & r5c9 form a unique quadrangle which leads to:
r5c8 Must only have 459 as valid Candidates (123 is a Naked Triple in Row 5)
*--------------------------------------------------------*
| 1     2     3    | 4     5     9    | 6     7     8    |
| 7     569   68   | 3     12    128  | 59    159   4    |
| 49    59    48   | 78    6    *17   | 2     1359 -135  |
|------------------+------------------+------------------|
| 3     1     2    | 56    9     4    | 7     8     56   |
| 8     7     46   | 256   12    123  | 59    459   356  |
| 49    69    5    | 68    7     38   | 1     34    2    |
|------------------+------------------+------------------|
| 6     8     7    | 1     3     25   | 4     25    9    |
| 2     3     1    | 9     4    *57   | 8     6    ^57   |
| 5     4     9    | 27    8     6    | 3     12   ^17   |
*--------------------------------------------------------*
Eliminating 1 from r3c9(ALS-XZ A=157 in r8c6, r3c6 B=157 in r8c9, r9c9  x=5 z=1)

Tarek

[Havard]

Here is another solution:

Code: Select all

*-----------------------------------------------------------*
 | 1     2     3     | 4     5     9     | 6     7     8     |
 | 7     569   68    | 3     12%   128%  | 59    159-  4     |
 | 49    59    48    | 78%   6     178   | 2     1359  135   |
 |-------------------+-------------------+-------------------|
 | 3     1     2     | 56    9     4     | 7     8     56    |
 | 8     7     46    | 256   12    123   | 59    3459  356   |
 | 49    69    5     | 68    7     38    | 1     34    2     |
 |-------------------+-------------------+-------------------|
 | 6     8     7     | 1     3     25    | 4     25    9     |
 | 2     3     1     | 9     4     57    | 8     6     57    |
 | 5     4     9     | 27#   8     6     | 3     12#   17    |
 *-----------------------------------------------------------*
ALS-XZ: x=7, z=1
Eliminating 1 from R2C8


solves the puzzle in a beautiful way!

havard

[ravel]

ALS-XZ: x=7, z=1

Thats what i want to spot in the puzzles since 2 weeks , but i failed again with this one - ok, keep on trying

[QBasicMac]

With all respect, it would be very nice if, at least from time to time, the progammers out there decide to try to solve a puzzle such as this one by hand, instead of just keep posting the output of the solvers (sometimes very long outputs).

Get here easily enough:

Code: Select all

+-------------+--------------+---------------+
| 1   2    3  | 4    5   9   | 6   7     8   |
| 7   569  68 | 3    12  128 | 59  159   4   |
| 49  59   48 | 78   6   178 | 2   1359  135 |
+-------------+--------------+---------------+
| 3   1    2  | 56   9   4   | 7   8     56  |
| 8   7    46 | 256  12  123 | 59  3459  356 |
| 49  69   5  | 68   7   38  | 1   34    2   |
+-------------+--------------+---------------+
| 6   8    7  | 1    3   25  | 4   25    9   |
| 2   3    1  | 9    4   57  | 8   6     57  |
| 5   4    9  | 27   8   6   | 3   12    17  |
+-------------+--------------+---------------+


Then try r9c9=1. By singles, solves easily.

OK, try r9c9=7. By singles gives an invalid puzzle.

Hence, by hand, there is one solution. No solver required


Mac, programmer