Hi David,
David P Bird wrote:Blue,
Using only strong sets for a (1367) set for selected rows and a complementary (24589) for selected columns this almost pattern can be found
- Code: Select all
*-------------------------*-------------------------*-------------------------*
13 | 134 248-13 123 | 4589 3589 <6> | <7> 2589-1 189 |
67 | 467 <5> 267 | <1> 789 489 | 289-6 <3> 689 |
| 1367 13678 <9> | 578 <2> 358 | 568 158 <4> |
*-------------------------*-------------------------*-------------------------*
| <2> 1367 1367-5 | 5789 137-589 13589 | 345689 145789 1367-89 |
| 1367-5 1367 <8> | 579 <4> 1359 | 3569 1579 <2> |
137 | <9> 137 <4> | <6> 13578 2 | 58-3 58-17 1378 |
*-------------------------*-------------------------*-------------------------*
13 | 1345 249-13 1235 | 24589 1589 <7> | 2489-3 <6> 389 |
67 | 4567 249-67 2567 | <3> 5689 4589 | <1> 2489-7 789 |
| <8> 1234679 1367-2 | 249 16-9 149 | 2349 2479 <5> |
*-------------------------*-------------------------*-------------------------*
45 25 589 89
Multi-Sector AHS (13)r1,(67)r2,(137)r6,(13)r7,(67)r8,(45)c1,(25)c3,(589)c5,(89)c9 20 candidates in 19 available cells
A few things to address in this post ...
First, it's a Multi-Sector ANS, not AHS -- "cell truths" in 19 cells, with candidates covered by 20 "row/column/box links".
Second, the items that you list ... (13)r1, ets ... are cover sets, not base sets as your first line would indicate.
If you want to use strong links for digits 1367, then you need to have them either in c1357 (your "selected columns"), or r3459 (your "unselected rows").
The PEs are shown but there are one too many of them as one of the digits must be false in the AHS, and therefore true in one peer cell outside it.
This can be confined to (5)b4 where there is a strong link between the two eliminated candidates, so the other 20 PEs are valid.
Now this can be converted to a Multi-Sector LS by removing (5) from the c13 covers and adding (5)b7
Multi-Sector AHS (13)r1,(67)r2,(137)r6,(13)r7,(67)r8,(4)c1,(2)c3,(589)c5,(89)c9,(5)b7 19 candidates in 19 available cells
No issues with this, except that it's an ANS again, candidates in 19 cells, covered by 19 row/column links ... the ones that you mention.
Side note (not important): Another way to deal with the "5's", is to add a box truth for digit 5 in b4, leading to a 20/20 problem -- one box and 19 cell truths, covered by the original 20 row/column links.
Item three: When you present these kinds of things, I would be grateful if you would list the cells as well. It was 19 in this case, and one of them (r6c2, containing candidates for digits 137, only) wasn't in the intersection of your "selected row" and "selected column" sets -- it was sort of a "special case", just like the 5 in b5. Actually I'ld be happiest if you'ld list the cells first (the base sets), and then the cover sets.
Item four -- not so important: I mentioned something about this to you in a PM. In this example, viewed as a base/cover problem, you can remove the 3 cell truths and row links in r6, and have a perfectly fine base/cover problem, with 16 cell truths, covered by 16 row/column/box links. You don't get the eliminations for 3r6c7 and 17r6c8 directly. Instead, you get eliminations for 58r6c5 and 8r6c9, leaving is a naked set for 137 in r6 that eliminates 3r6c7 and 17r6c8. Note: If you're using XSudo, and you plug the 19 cell truths and 19 cover sets (using 5b7, rather than 5c1 and 5c3), then it shows all 6 eliminations, but the ones for 58r6c5 and 8r6c9 are shown as "cannibal eliminations".
Best Regards,
Blue.
P.S. For XSudo users (and David as well), here are a couple more takes on things, inspired by David's post:
This one has row truths for 1367 in r3459 (an option mentioned above), and highlights the special situations for 5b5 and r6c2.
18 Truths = {1R3459 3R3459 6R3459 7R3459 6N2 5B4}
18 Links = {1367c2 7c4 13c6 36c7 17c8 3n1 4n359 5n1 9n35}
20 Eliminations --> r4c5<>589, r1c28<>1, r7c27<>3, r8c28<>7, r4c9<>89, r6c8<>17, r1c2<>3,
r2c7<>6, r6c7<>3, r7c2<>1, r8c2<>6, r9c3<>2, r9c5<>9,
This one has row truths for 1367 in r34569 (one more row).
The special circumstance for r6c2, has gone away.
The eliminations are different too -- with differences confined to r6.
20 Truths = {1R34569 3R34569 6R3459 7R34569 5B4}
20 Links = {1367c2 7c4 13c6 36c7 17c8 35n1 49n3 469n5 46n9}
20 Eliminations --> r4c5<>589, r1c28<>1, r6c59<>8, r7c27<>3, r8c28<>7, r4c9<>89, r1c2<>3,
r2c7<>6, r6c5<>5, r7c2<>1, r8c2<>6, r9c3<>2, r9c5<>9,