The New Sudoku Players' Forum

[Jasper32]

I think I have enclosed a puzzle with a Su De Coq. There seems to be little written about Sue De Coq's logic and I would like to know more about them. I think they are not all that isolated in puzzles.

I know there are a lot of eliminations that could be made at this point in the puzzle but I wish to dwell on just the Sue De Coq.

The (a's) on the puzzle are the (3) cells with (5) candidates...2/4/5/6/9
The (b's) are the bivalves. 24, 49

Is there a "rule of thumb" to help me identify what candidates can be eliminated in a Sue De Coq?

My questions:
(1) Is this a Su de Coq?
(2) What candidates can be excluded?
(3) If there are candidates that can be excluded, what is the logic that allows them to be excluded.

It seems the (4) in r2c8 can be excluded and I believe this is because it is at the intersection of the (4's) in r2c4 and r3c8.

You have all been so helpful to be and I want to thank you.

Code: Select all


 *-----------*
 |...|97.|..8|
 |37.|.1.|...|
 |1..|.65|..3|
 |---+---+---|
 |..3|...|87.|
 |9..|...|..1|
 |.16|...|4..|
 |---+---+---|
 |4..|826|..7|
 |...|.3.|.29|
 |6..|.91|...|
 *-----------*

 
 *-----------------------------------------------------------------------------*
 | 25      2456    245     | 9       7       234     | 1256    1456    8       |
 | 3       7       24589   | 24b      1       248     | 2569a    4569a    2456a    |
 | 1       2489    2489    | 24      6       5       | 279     49b      3       |
 |-------------------------+-------------------------+-------------------------|
 | 25      245     3       | 12456   45      249     | 8       7       256     |
 | 9       2458    24578   | 234567  458     23478   | 2356    356     1       |
 | 2578    1       6       | 2357    58      23789   | 4       359     25      |
 |-------------------------+-------------------------+-------------------------|
 | 4       359     159     | 8       2       6       | 135     135     7       |
 | 578     58      1578    | 457     3       47      | 156     2       9       |
 | 6       2358    2578    | 457     9       1       | 35      3458    45      |
 *-----------------------------------------------------------------------------*




[999_Springs]

Your 5 values in 3 cells are fine (it can also be 4 values in 2 cells as another possibility), but the problem with your bivalue cells is that all four values in both bivalue cells must be different, so your Sue de Coq isn't one.
Eliminations are made in a somewhat different way. Here is the only example of a Sue de Coq that I have ever encountered:

Code: Select all

    14      2      3 ||     7      5      9 ||   148     148       6
     8      7     14 ||     2      6    134 ||     5       9     134
     9     56     56 ||   138    138   1348 ||     7       2     134
=====================||=====================||======================
    26    156  12568 ||  1358      4    138 ||     9       7     158
     3    145      7 ||   158      9      6 ||   148    1458       2
    14   1459  14589 ||   158      2      7 ||    36      36    1458
=====================||=====================||======================
     5   1369   1269 ||     4      7    138 || 12368    1368     189
    67  13469   1469 ||    69    138      2 || 13468  134568  145789
   267      8  12469 ||    69     13      5 || 12346    1346    1479

The 4 values in 2 cells are 1456r45c2 and the bivalue cells are r6c1 and r3c2. Now 5 and 6 can be eliminated from the rest of column 2 other than the stated cells because they can see the bivalue cell r3c2 and the two cells r45c2. Similarly 1 and 4 can be eliminated from the rest of block 4.
So r4c3<>1, r6c3<>14, r7c2<>6, r8c2<>6 and r6c2<>145 (it is in both c2 and b4). There are no eliminations in the cells directly involved.

By the way your puzzle is singles-only until a very late stage and then needs an XY-wing and a 3 strong links.

[Jasper32]

Thanks 999_Springs for replying to my post. It was clearest explanation I have read about Sue Do Coq. Your help is appreciated.

Many thanks.

[hobiwan]

Hello Jasper32,

IMO the clearest explanation is still in the original Thread here (read Sue de Coq's second post).

[DonM]

IMO the clearest explanation is still in the original Thread here (read Sue de Coq's second post).

Jasper, I don't find that explanation particularly clear at all (though it was written by the rubylips, the originator of Sue de Coq) which is why I started this thread with a tutorial that I think makes an SDC easier to find:

http://forum.enjoysudoku.com/viewtopic.php?t=6410