pjb wrote:In regard to Exotic Patterns, I've noticed the term 'almost SK-loop', but haven't seen much discussion around eliminations that are associated with it.
...
I compared the patterns to the solved puzzles and found in every case that the eliminations within the 4 boxes were valid, but that in every case the eliminations for one of the rows (or columns) produced an invalid result. Therefore, at least on the basis of this small sample, it seems safe to make the eliminations within the boxes as per normal SK loop, but not in the rows and columns.
Almost sk-loop simply means the sk-loop is slightly flawed. The puzzle looks very much like an sk-loop, but because of at least one "flaw", it isn't one. For example, in the first of your list,
champagne dry, the clue r4c6=5 would be r4c6=4 in an unflawed sk-loop.
An almost sk-loop usually has only a very few of the same exclusions as the pure sk-loop to which it is similar, indeed, often only one exclusion. For the
champagne dry, there are no exclusions using just the usual 2-row 2-col strong inference sets ("truths"). Two more truths are required, specifically the r3c12=1234 AALS, to link the <1234>-layers. These two additional truths reduce the k-rank sufficiently to yield an exclusion. You may note this r2c4<>8 exclusion is the same as for the exocet pattern for this puzzle.
[edit: Any additional exclusion(s) would require at least one additional truth.]___
(clickable image)
- Code: Select all
980700000700000600006050000040005030007900500000020001008500900000010004000003020
17 Truths = {123R5 1234R7 1234C47 3N12}
21 Links = {1234r3 4r6 1234c1 123c2 2n4 1n7 1b59 2b68 3b59 4b8}
champagne wrote:A lot of puzzles have some similarities with the SK loop, but I know no logic derived from the SK loop to justify eliminations.
There's one immediately above.
champagne wrote:In your list, I have seen puzzles having an exocet pattern, puzzles having a rank 0 logic, Each of these properties leads to some eliminations.
If you mean a
0-rank almost sk-loop, it would have
exactly the same exclusions as the sk-loop.
champagne wrote:...if you have a constant coherency in the boxes doing eliminations in a SK loop mode, may be we have missed another property.
Agreed, but as noted above, more strong inference sets would be required.
champagne wrote:... misuse of the word SK loop is frequent and started with our friend Allan Barker using the expression (SK loop and not Almost SK loop) ...
I would be surprised if that were true, so p
lease provide a link.
(thumbnail only)
