The New Sudoku Players' Forum

[Yogi]

745281.3..1.956..7629374158.84.92.7.9.7.1...42..74....59..278.3432869715.7..35.92

After some eliminations I get to here:

Code: Select all

+-------------+-------------+-------------+
| 7   4   5   | 2   8   1   | 69  3   69  |
| 38  1   38  | 9   5   6   | 24  24  7   |
| 6   2   9   | 3   7   4   | 1   5   8   |
+-------------+-------------+-------------+
| 13  8   4   | 56  9   2   | 356 7   16  |
| 9   56  7   | 56  1   38  | 23  28  4   |
| 2   56  13  | 7   4   38  | 359 68  19  |
+-------------+-------------+-------------+
| 5   9   16  | 14  2   7   | 8   46  3   |
| 4   3   2   | 8   6   9   | 7   1   5   |
| 18  7   168 | 14  3   5   | 46  9   2   |
+-------------+-------------+-------------+


It should be simple to finish off but I can't find anything.

[jco]

Hi Yogi,

Lots of bivalue cells induce one to search for xy-chains.

Code: Select all

,--------------------------------------------------,
| 7    4    5    | 2    8    1    | 69   3    69   |
| 38   1    38   | 9    5    6    | 24   24   7    |
| 6    2    9    | 3    7    4    | 1    5    8    |
|----------------+----------------+----------------|
|*13   8    4    | 56   9    2    | 356  7   *16   |
| 9    56   7    | 56   1    38   | 23   28   4    |
| 2    56   1-3  | 7    4   *38   | 359 *68   19   |
|----------------+----------------+----------------|
| 5    9    16   | 14   2    7    | 8    46   3    |
| 4    3    2    | 8    6    9    | 7    1    5    |
| 18   7    168  | 14   3    5    | 46   9    2    |
'--------------------------------------------------'

An easier way to find xy-chains is to search for sequences of pairs of numbers with the same digits between adjacent
elements with the same initial and final digit seeing a common target.
We have 31-16-68-83 in cells r4c1, r4c9, r6c8, r6c6 eliminating 3 from r6c3, i.e.,

(3=1)r4c1 - (1=6)r4c9 - (6=8)r6c8 - (8=3)r6c6 => -3 r6c3; ste

Another way: 68-83-31-16 in cells r6c8,r6c6,r6c3 and r7c3 eliminating 6 from r7c8.

[Yogi]

VGood!

Thanx

[RSW]

A short solution involving an almost locked set:

Code: Select all

 +-------------+----------+---------------+
 | 7   4   5   | 2  8  1  | 69    3   69  |
 | 38  1   38  | 9  5  6  | 24    24  7   |
 | 6   2   9   | 3  7  4  | 1     5   8   |
 +-------------+----------+---------------+
 |*3-1 8   4   | 56 9  2  | 356   7  b16  |
 | 9   56  7   | 56 1  38 | 23    28  4   |
 | 2   56 a13  | 7  4 a38 | 3569 a68 *69-1|
 +-------------+----------+---------------+
 | 5   9   16  | 14 2  7  | 8     46  3   |
 | 4   3   2   | 8  6  9  | 7     1   5   |
 | 18  7   168 | 14 3  5  | 46    9   2   |
 +-------------+----------+---------------+


(1=386)r6c368 - (6=1)r4c9 => -1r4c1 -1r6c9; stte

[Yogi]

I just made an interesting observation. I’ve been trying to learn how to use Type2 AICs to solve Naked Pairs and I’ve realized that both JCO’s suggestions become just that if you continue the XY-Chain into the eliminating cell. Then you have that situation where the starting candidate cannot be true in the end cell and the end candidate cannot be true in the starting cell. Of course it is much simpler when you can get right through on bivalue cells, but it does give another option when the XY-Chain doesn’t quite connect right round to where you would like to get to.

[StrmCkr]

http://forum.enjoysudoku.com/post316236.html#p316236
check this post out for reference 2nd example.

(1) 4 = 4 (2) - (2) 0 = 0 (1)

the ending cell is a peer of the first cell with same digit then
all strong links are weak, and all weak links are strong.

(1) 4 - 4 (2) = (2) 0 - 0 (1)

and then apply eliminations for all strong links of both cases.

anything peer of 0,4 for both 1& 2 <> 1,2

Code: Select all

+--------------+-------------+---------------+
| 7   4   5    | 2   8  1    | 69   3     69 |
| 38  1   38   | 9   5  6    | 24   24    7  |
| 6   2   9    | 3   7  4    | 1    5     8  |
+--------------+-------------+---------------+
| 13  8   4    | 56  9  2    | 356  7     16 |
| 9   56  7    | 56  1  38   | 23   28    4  |
| 2   56  (13) | 7   4  (38) | 359  (68)  19 |
+--------------+-------------+---------------+
| 5   9   (16) | 14  2  7    | 8    4-6   3  |
| 4   3   2    | 8   6  9    | 7    1     5  |
| 18  7   168  | 14  3  5    | 46   9     2  |
+--------------+-------------+---------------+

another solution:

Code: Select all

wxyz wing
    als a) 1368  @ R6C368
    als b) 16 @ R7C3
      x: 1
      z: 6 
   R7C8 <> 6