## Hodoku Sue de Coq in 2015

This post reveals the Hodoku view of Sue de Coq, reflecting an earlier expert consensus, to be dated. His classic examples are good, but the examples of Hodoku’s “Extended Variation” of Sue de Coq are better interpreted as simply the use of multi-cell ALS along with bv. Except for the last one, which steps outside of the traditional definition to expand further the role of ALS in Sue de Coq. Any update of Sue de Coq must now  include the SASdC, the single alternate form that is a basis for trials. The concept of trials is a Hodoku update issue in itself.

Hodoku begins the Sue de Coq page with the statement that SdC is a variant of subset counting, a mechanical search process totally unsuited to human solving. Actually the question is, what isn’t?

The examples begin with classical SdC with chute matching bv in box and row remainders. Hodoku covers the two classic types, single clue with four numbers and the clueless with five. In his definition, Hobiger makes the unnecessary restriction that only one of the bv can occupy a remainder. And he omits the two clue, single free cell variation with a single alternate.

Here is the second example, a clueless classic with chute SEr9 contents described by 4(2+7)(5+6). This type of logical description is missing from Hodoku, as it was from the original SdC post.

Extra 2’s are removed from the box remainder and the extra 5 and 6, from the line remainder. The chute must contain true 4, therefore the remainders don’t.

“Sue” thought that SdC was soon to be overshadowed by forcing chains. Experts of the day thought it rare and overcomplicated. Hodoku goes along, filing Sue de Coq as the only topic under Miscellaneous – an undeserved snub. SdC is an easily spotted technique exploiting bv. It is among the first techniques I look for on the line marked grid.

A mistake common in Hodoku’s time was to overlook the role of multi-cell ALS in Sue de Coq. The Hobiger description, and presumably his program, continues to confine “basic” Sue de Coq to bv. In contrast, Andrew Stuart in his The Logic of Sudoku (2006) features a two cell ALS in his primary classic SdC example.

Hodoku followed the wrong experts, and missed multi-cell ALS, even though he was demonstrating elsewhere a command of ALS.  Citing an elaborate formal definition from programmer forums , Hobiger proposed an “Extended Variation” SdC, which is actually classic SdC with multi-cell ALS. I’m revising my Sysudoku Sue de Coq post, to include one of his examples. Here is the other one.

In this triumph of puzzle composition, two ALS define the classic Sue de Coq alternate pairs, eliminating 1 and 9 from the West box, and 2 and 3 from the c1 column. Of course ALS have the disadvantage in the SdC of using up cells that could have removals. But since an ALS can give up one number only, they have the advantage of containing true candidates of any extra number. Here that advantage is illustrated in both remainders. The green ALS supplies (1+9) and must contain 5, removing three in W. The blue ALS supplies (2+3) and must contain 4, removing five candidates, and confirming SE4, SE2, and W4. Tell ‘em where you saw it.

It wasn’t on Hodoku. That version currently misses the remarkable reach of the blue ALS and 4r8c1. His code for the “Extended Type” of Sue de Coq removes only the other 4 in remainder, 4r7c1.

A similar, but less spectacular failing occurs in the next Extended Type example, which you might like to analyze yourself. Again, it’s a classic Sue de Coq with two-cell ALS in place of bv. I’ll checkpoint you on that one next post.

Hodoku’s current last example in this section is something that Sue never imagined. It fits under the “formal “ definition of SdC that the forum experts devised to cover all cases, and which is quoted for your convenience and wonder on Hodoku . The definition allows a cell of the Sue de Coq chute to be incorporated into one or both of the remainder ALS. Here is the Hodoku example:

It is the contents of r34c4 that are described by a logical expression. The column remainder bv 39 is joined by the N box ALS 1678 in restricting those contents to the logical expression r23c4=(3+9)(1+6+8). We don’t need to wade through the formal SdC definition. What we know about ALS is enough:

Since the box ALS must supply one of 1, 6, or 8 to r34c4, the other cells of the box remainder cannot have the 1, 6, or 8. Or even the 7, because an ALS can give up only one number. The wipe out in the box is too cluttered to even draw. You can verify that the collapse follows immediately.

If you tried to transcribe this from the Hodoku site, you might notice that I treated the blue 7r8c8 as a given. Otherwise I don’t know where this clue comes from.

I take this chute raiding variation to be fully in line with Sue de Coq logic. I have yet to look for one of these in my bv scan, so my blog is dated on that.

Bernhard’s examples illuminate classic, ALS aided Sue de Coq well. He needs to put away his Extended Variation labeling with the ALS driven classic approach illustrated here, bringing ALS detecting routines to bear on it. And he needs to give Sue de Coq a better treatment on the Hodoku Techniques list.

Also, at the meta solving level, Bernhard needs to consider the place of Single Alternate Sue de Coq, and other logically constructed trials, in Hodoku. His starting premise for every technique, which actually conceals a large number of arbitrary premises, will be a major topic in this review.

By now I’m sure you are less than thrilled with Hodoku color coding as you go back and forth between web pages. A challenge for Bernhard to introduce curves and pencil mark coloring to Hodoku might appeal to him. Bernhard, you’re welcome to the Sysudoku drawing conventions. I do them by hand in ©PowerPoint.

Next time, I’m reviewing the current Hodoku Wings page. Hodoku dismisses the WXYZ as too rare for serious attention. You and I can agree, based on personal experience, but let’s put our order in for a Hodoku repertoire expansion into BARN and BNS under separate headings.