The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |6..|...|...|
 |...|..3|74.|
 |..2|...|.8.|
 |---+---+---|
 |...|83.|4.7|
 |...|4..|9..|
 |.3.|..2|..8|
 |---+---+---|
 |.8.|94.|3..|
 |.24|...|.19|
 |...|2.1|.6.|
 *-----------*


Play/Print this puzzle online

[SteveG48]

Code: Select all

 *-----------------------------------------------------------*
 | 6     1457  1357  | 157   178   478   | 2     9     35    |
 | 8     159   159   | 156   2     3     | 7     4     56    |
 | 357   457   2     | 567  c79    479   | 1     8     356   |
 *-------------------+-------------------+-------------------|
 | 59    1569  159   | 8     3     69    | 4     2     7     |
 | 2     67    8     | 4     5     6-7   | 9     3     1     |
 | 4     3     79    |d17   c179   2     | 6     5     8     |
 *-------------------+-------------------+-------------------|
 | 1     8     6     | 9     4     5     | 3     7     2     |
 | 57    2     4     | 3     6    a78    | 58    1     9     |
 | 3579  579   3579  | 2    b78    1     | 58    6     4     |
 *-----------------------------------------------------------*


(7)r8c6 = r9c5 - (7=19)r36c5 - (1=7)r6c4 => -7 r5c6 ; stte

[Leren]

Code: Select all

*--------------------------------------------------------------*
| 6     1457  1357   |c157   178   478    | 2     9     35     |
| 8     159   159    | 156   2     3      | 7     4     56     |
| 357   457   2      |c567  d79    479    | 1     8     356    |
|--------------------+--------------------+--------------------|
| 59    1569  159    | 8     3     69     | 4     2     7      |
| 2     67    8      | 4     5     67     | 9     3     1      |
| 4     3    a79     |b17    17-9  2      | 6     5     8      |
|--------------------+--------------------+--------------------|
| 1     8     6      | 9     4     5      | 3     7     2      |
| 57    2     4      | 3     6     78     | 58    1     9      |
| 3579  579   3579   | 2     78    1      | 58    6     4      |
*--------------------------------------------------------------*

W Wing (7-9) with Group S/L on 7 : (9=7) r6c3 - r6c4 = r13c4 - (7=9) r3c5 => - 9 r6c5; stte

Leren

[pjb]

Code: Select all

 6      1457   1357   | 157    178    478    | 2      9      35     
 8      159    159    | 156    2      3      | 7      4      56     
 357    457    2      | 567    79     479    | 1      8      356   
 ---------------------+----------------------+---------------------
c59     1569   159    | 8      3     b69     | 4      2      7     
 2      67     8      | 4      5     a67     | 9      3      1     
 4      3      79     | 17     179    2      | 6      5      8     
 ---------------------+----------------------+---------------------
 1      8      6      | 9      4      5      | 3      7      2     
d57     2      4      | 3      6      8-7    | 58     1      9     
 3579   579    3579   | 2      78     1      | 58     6      4     


XY chain: (7=6)r5c6 - (6=9)r4c6 - (9=5)r4c1 - (5=7)r8c1 => -7 r8c6; stte

Phil

[ArkieTech]

Code: Select all

 *-----------------------------------------------------------*
 | 6     1457  1357  |b157   178   478   | 2     9     35    |
 | 8     159   159   |b156   2     3     | 7     4     56    |
 | 357   457   2     |b567  b79    479   | 1     8     356   |
 |-------------------+-------------------+-------------------|
 | 59    1569  159   | 8     3     69    | 4     2     7     |
 | 2     67    8     | 4     5     67    | 9     3     1     |
 | 4     3    a79    |a17    17-9  2     | 6     5     8     |
 |-------------------+-------------------+-------------------|
 | 1     8     6     | 9     4     5     | 3     7     2     |
 | 57    2     4     | 3     6     78    | 58    1     9     |
 | 3579  579   3579  | 2     78    1     | 58    6     4     |
 *-----------------------------------------------------------*
(9=1)r6c34-(1=9)r123c4,r3c5 => -9

[Marty R.]

Code: Select all

+----------------+-------------+----------+
| 6    1457 1357 | 157 178 478 | 2  9 35  |
| 8    159  159  | 156 2   3   | 7  4 56  |
| 357  457  2    | 567 79  479 | 1  8 356 |
+----------------+-------------+----------+
| 59   1569 159  | 8   3   69  | 4  2 7   |
| 2    67   8    | 4   5   67  | 9  3 1   |
| 4    3    79   | 17  179 2   | 6  5 8   |
+----------------+-------------+----------+
| 1    8    6    | 9   4   5   | 3  7 2   |
| 57   2    4    | 3   6   78  | 58 1 9   |
| 3579 579  3579 | 2   78  1   | 58 6 4   |
+----------------+-------------+----------+


Play this puzzle online at the Daily Sudoku site

XY-Wing with transport.

(7=5)r8c1-(5=9)r4c1-(9=7)r6c3-r6c45=r5c6=>r8c6<>7

[Sudtyro2]

Code: Select all

*--------------------------------------------------------------*
| 6     1457  1357   |d157   178   478    | 2     9     35     |
| 8     159   159    | 156   2     3      | 7     4     56     |
| 357   457   2      |d567  a9-7   479    | 1     8     356    |
|--------------------+--------------------+--------------------|
| 59    1569  159    | 8     3     69     | 4     2     7      |
| 2     67    8      | 4     5     67     | 9     3     1      |
| 4     3     79     |c17   b179   2      | 6     5     8      |
|--------------------+--------------------+--------------------|
| 1     8     6      | 9     4     5      | 3     7     2      |
| 57    2     4      | 3     6     78     | 58    1     9      |
| 3579  579   3579   | 2     78    1      | 58    6     4      |
*--------------------------------------------------------------*

AIC: (9)r3c5=(9-1)r6c5=(1-7)r6c4=(7)r13c4 => r3c5<>7; stte

SteveC

[Sudtyro2]

Code: Select all

*--------------------------------------------------------------*
| 6     1457  1357   |c157  a178   478    | 2     9     35     |
| 8     159   159    |c156   2     3      | 7     4     56     |
| 357   457   2      |c567  b9-7   479    | 1     8     356    |
|--------------------+--------------------+--------------------|
| 59    1569  159    | 8     3     69     | 4     2     7      |
| 2     67    8      | 4     5     67     | 9     3     1      |
| 4     3     79     | 17    179   2      | 6     5     8      |
|--------------------+--------------------+--------------------|
| 1     8     6      | 9     4     5      | 3     7     2      |
| 57    2     4      | 3     6     78     | 58    1     9      |
| 3579  579   3579   | 2    d78    1      | 58    6     4      |
*--------------------------------------------------------------*

And just to make the previous easy exclusion hard....use an APE:

Aligned pair marked a/b: r1c5/r3c5
All pair combinations: 1/7, 1/9, 7/7, 7/9, 8/7, 8/9

Combination 1/7 not allowed because it would leave ALS(1567)r123c4 with 3 cells and only 2 candidates to fill them.
Combination 7/7 is impossible.
Combination 8/7 is not allowed because it would eliminate both candidates in r9c5.

No a/b combination remains having b=7, => r3c5<>7; stte

SteveC

[Luke]

And just to make the previous easy exclusion hard....use an APE:

I prefer and champion the oddball solutions! But...

Aligned pair exclusion is considered a dead process by most. It is subsumed by als-xz, as well as other and more basic techniques. I'll point out the als-xz if you'd like.

And SteveC, I'd like to mention that I am very interested how *you* would solve this puzzle. Why not acknowledge program generated solutions when you utilize them?

[Sudtyro2]

And SteveC, I'd like to mention that I am very interested how *you* would solve this puzzle. Why not acknowledge program generated solutions when you utilize them?

Thx, Luke, for your comments. I'm new to this topic, so am not yet fully aware of the "rules" of play. Initially, I sent a PM to ArkieTech (Dan) with a query to that effect and asked about how the starting pencil-marked grid is developed and which "basic" methods are used. I have no codes of my own, but was advised that one could download and use SImple Sudoku to generate the starting grid, which appears to stop at the "locked-set" point. I further mentioned to Dan that I sometimes use Andrew Stuart's online solver http://www.sudokuwiki.org/sudoku.htm when I hit a dead-end solving manually. Dan was apparently not familiar with the site.

The simple AIC solution presented above is my own and was developed after seeing Leren's solution and its exclusion of (9)r6c5, which then immediately places (9)r3c5 and excludes (7)r3c5. My chain used the same grouped 7s in r13c4 as Leren's did (plus two more of his chain's nodes), but obviously starts off with the (9) in the CEC...all just a minor tweak on Leren's approach.

I, too, like the oddball solutions, so I then went to Andrew's solver to look for something "different." His solver turned up the listed APE, among several other solutions from his "Diabolical" and "Extreme" strategies sections. As you mentioned, the APE method is subsumed by several others, but I find it interesting, nevertheless, and thought other players might be interested, as well. Rest assured that I would never have spotted the APE on my own. And I agree that use of outside codes should always be acknowledged.

SteveC

[DonM]

When there were far more manual solvers and more than one 'active' solving forum, there was a relative collective understanding of the 'current norm' of solving. For instance, the use of AIC notation was accepted as the standard (nice loop notation was essentially dead), the basics of how AIC notation was used was fairly standard and there was a consensus/understanding as to which solving methods were now outdated or subsumed by others.

Since the above (ie. the 'understanding' or consensus) is no longer on-going, there has developed an unfortunate re-inventing of the wheel. And one of the reasons for that is the use of computer solvers that spit out solutions based on long-outdated methods and using long-outdated terminology. (That, incidentally, is one of the give-aways of the use of computer solvers on this forum.) If it is not made clear by the poster that what is really an out-dated method is from a computer solver and is posted just for interest sake, then newer solvers are going to think that they have just found a 'new' method for use. IMO, this is the reason that, from time-to-time, we also see a solution posted using nice loop notation or some definition based on nice loop notation.