The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |...|.3.|.7.|
 |...|.24|15.|
 |65.|...|...|
 |---+---+---|
 |19.|..2|5..|
 |8..|7.3|..9|
 |..5|9..|.62|
 |---+---+---|
 |...|...|.85|
 |.86|39.|...|
 |.2.|.7.|...|
 *-----------*


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[SteveG48]

Code: Select all

 *--------------------------------------------------------------------*
 | 2     d14    e148    | 5      3      9      | 68     7      468    |
 | 379   c37     3789   | 6      2      4      | 1      5      38     |
 | 6      5     e34     | 18     18     7      | 29     29     34     |
 *----------------------+----------------------+----------------------|
 | 1      9      7-4    |a48     6      2      | 5      3      78     |
 | 8      6      2      | 7      5      3      | 4      1      9      |
 | 347   c347    5      | 9     b148    18     | 78     6      2      |
 *----------------------+----------------------+----------------------|
 | 3479  c1347   13479  | 2     b14     16     | 3679   8      5      |
 | 457    8      6      | 3      9      15     | 27     24     17     |
 | 3459   2      1349   | 148    7      1568   | 369    49     16     |
 *--------------------------------------------------------------------*


4r4c4 = (14)r67c5 - (1=347)r267c2 - 4r1c2 = 4r13c3 => -4 r4c3 ; stte

[pjb]

Code: Select all

 2      d14     c148    | 5      3      9      | 68     7      468   
 379     37      3789   | 6      2      4      | 1      5      38     
 6       5      c34     | 18     18     7      | 29     29     34     
------------------------+----------------------+---------------------
 1       9      b47     |a48     6      2      | 5      3      78     
 8       6       2      | 7      5      3      | 4      1      9     
 347     347     5      | 9      18-4   18     | 78     6      2     
------------------------+----------------------+---------------------
 3479   e1347    13479  | 2     f14     16     | 3679   8      5     
 457     8       6      | 3      9      15     | 27     24     17     
 3459    2       1349   | 18-4   7      1568   | 369    49     16     


(4)r4c4 = r4c3 - r13c3 = (4-1)r1c2 = r7c2 - (1=4)r7c5, => -4 r6c5, r9c4; stte

Phil

[Cenoman]

Code: Select all

 +------------------------+---------------------+--------------------+
 |  2     a14#    148*    |  5     3     9      |  68     7    468*  |
 |  379    37     3789    |  6     2     4      |  1      5    38    |
 |  6      5      34*     |  18    18    7      |  29     29   34*   |
 +------------------------+---------------------+--------------------+
 |  1      9      7-4     | e48    6     2      |  5      3    78    |
 |  8      6      2       |  7     5     3      |  4      1    9     |
 |  347    347    5       |  9    d148   18     |  78     6    2     |
 +------------------------+---------------------+--------------------+
 |  3479  b1347   13479   |  2    c14    16     |  3679   8    5     |
 |  457    8      6       |  3     9     15     |  27     24   17    |
 |  3459   2      1349    |  148   7     1568   |  369    49   16    |
 +------------------------+---------------------+--------------------+

Almost X-wing (4)r13 + rfr1c2
[XW(4)r1c3*=r1c9-r3c9=r3c3]
(4-1)r1c2 = r7c2 - (1=4)r7c5 - r6c5 = (4)r4c4
=> -4 r4c3; stte

[Ngisa]

Code: Select all

+---------------------------+------------------------+-----------------------+
| 2         14        148   | 5        3        9    | 68        7       468 |
| 379       37        3789  | 6        2        4    | 1         5       38  |
| 6         5         34    | 18       18       7    | 29        29      34  |
+---------------------------+------------------------+-----------------------+
| 1         9         47    |d48       6        2    | 5         3       78  |
| 8         6         2     | 7        5        3    | 4         1       9   |
| 347       347       5     | 9       c148     c18   |b78        6       2   |
+---------------------------+------------------------+-----------------------+
| 3479      1347      13479 | 2        14       16   | 3679      8       5   |
| 457       8         6     | 3        9        15   |a27       g4-2     17  |
| 3459      2         349   |e148      7        1568 | 369      f49      16  |
+---------------------------+------------------------+-----------------------+


(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4)r8c8 => - 2 r8c8; lclste

Clement

[Marty R.]

Code: Select all

+---------------------------+------------------------+-----------------------+
| 2         14        148   | 5        3        9    | 68        7       468 |
| 379       37        3789  | 6        2        4    | 1         5       38  |
| 6         5         34    | 18       18       7    | 29        29      34  |
+---------------------------+------------------------+-----------------------+
| 1         9         47    |d48       6        2    | 5         3       78  |
| 8         6         2     | 7        5        3    | 4         1       9   |
| 347       347       5     | 9       c148     c18   |b78        6       2   |
+---------------------------+------------------------+-----------------------+
| 3479      1347      13479 | 2        14       16   | 3679      8       5   |
| 457       8         6     | 3        9        15   |a27       g4-2     17  |
| 3459      2         349   |e148      7        1568 | 369      f49      16  |
+---------------------------+------------------------+-----------------------+


(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4)r8c8 => - 2 r8c8; lclste

Clement

Hi,

How should we address you? Is your name Ngisa or Clement?

I'm having trouble understanding the conclusion. Of course if r8c8=4, then it's not 2. But I don't see where the opening term of (2=7)r8c7 excludes that 2 from r8c8.

[pjb]

The chain shows that if r8c7 is not 2, then r8c8 is not 2. If r8c7 is 2, then again r8c8 is not 2.
Phil

[Ngisa]

Code: Select all

+---------------------------+------------------------+-----------------------+
| 2         14        148   | 5        3        9    | 68        7       468 |
| 379       37        3789  | 6        2        4    | 1         5       38  |
| 6         5         34    | 18       18       7    | 29        29      34  |
+---------------------------+------------------------+-----------------------+
| 1         9         47    |d48       6        2    | 5         3       78  |
| 8         6         2     | 7        5        3    | 4         1       9   |
| 347       347       5     | 9       c148     c18   |b78        6       2   |
+---------------------------+------------------------+-----------------------+
| 3479      1347      13479 | 2        14       16   | 3679      8       5   |
| 457       8         6     | 3        9        15   |a27       g4-2     17  |
| 3459      2         349   |e148      7        1568 | 369      f49      16  |
+---------------------------+------------------------+-----------------------+


(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4)r8c8 => - 2 r8c8; lclste

Clement

Hi,

How should we address you? Is your name Ngisa or Clement?

I'm having trouble understanding the conclusion. Of course if r8c8=4, then it's not 2. But I don't see where the opening term of (2=7)r8c7 excludes that 2 from r8c8.

If r8c7 is 2, then, r8c8 cannot be 2. (I did not put it in the opening term, because it is understood that if r8c7 is 7 it cannot be 2).
If r8c7 is 7, r8c8 is 4. Whichever the solution in r8c7 (2,7); r8c8 cannot be 2. Is this clear?
My first name is Clement which I use in other sudoku columns. Ngisa is my second name, I was denied to register with the first name in this column because there was another person using that name as I have pointed above. In order not to lose my identity, I have to sign it in my submissions. So, they are all my names, no problem.

[Marty R.]

If r8c7 is 7, r8c8 is 4. Whichever the solution in r8c7 (2,7); r8c8 cannot be 2. Is this clear?

No, I'm sorry, it's not clear to me. I am locked on to the fact that there are just two 2s in r8 and b9. If r8c7=7, then it's not 2 and r8c8 must be =2. since it's the only other one available.

[eleven]

If r8c7 is 7, r8c8 is 4. Whichever the solution in r8c7 (2,7); r8c8 cannot be 2. Is this clear?

No, I'm sorry, it's not clear to me. I am locked on to the fact that there are just two 2s in r8 and b9. If r8c7=7, then it's not 2 and r8c8 must be =2. since it's the only other one available.

Marty,

if you follow the chain, it says that if r8c7=7, that r8c8=4. So you have a contradiction, and r8c7 cannot be 7.
If you have trouble to understand the conclusion
(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4)r8c8 => - 2 r8c8
here you can just add one more link:
(4=2)r8c8-(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4)r8c8 => 4 r8c8
or
(2=7)r8c7 - (7=8)r6c7 - r6c56 = (8-4)r4c4 = r9c4 - r9c8 = (4-2)r8c8 = 2r8c7=> 2 r8c7
Both 4r8c8 and 2r8c7 imply, that r8c8 cannot be 2.

But generally, if 2 cells see one another, say r1c1 with candidates 12345 and r1c4 with candidates 34567, and you have a chain 3r1c1=....=4r1c4 (either 3 is in r1c1 or 4 in r1c4), you can eliminate 3 from r1c4 (if it is not 4, r1c1 must be 3) and 4 from r1c1 (if it is not 3, r1c4 must be 4).

[Marty R.]

if you follow the chain, it says that if r8c7=7, that r8c8=4. So you have a contradiction, and r8c7 cannot be 7.

OK, thanks, got it. For years I've been looking at the first term to see if it forces the same conclusion as the ending term. In this case I just didn't see it and didn't think about it enough.