The New Sudoku Players' Forum

[ArkieTech]

Code: Select all

 *-----------*
 |9..|..8|..5|
 |..2|3.5|8.6|
 |...|..2|.1.|
 |---+---+---|
 |3..|...|...|
 |.25|...|39.|
 |...|...|7.4|
 |---+---+---|
 |.8.|6..|...|
 |2.3|5.4|1..|
 |7..|9..|..3|
 *-----------*


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[JC Van Hay]

Code: Select all

+--------------------+--------------------+---------------------+
| 9     1467   1467  | 147    147     8   | 2      3      5     |
| 14    147    2     | 3      9       5   | 8      47     6     |
| 5     3      8     | 47     6       2   | -4(9)  1      7(9)  |
+--------------------+--------------------+---------------------+
| 3     14679  14679 | 12478  124578  679 | 56     2568   128   |
| 1468  2      5     | 1478   1478    67  | 3      9      18    |
| 168   169    169   | 128    12358   369 | 7      2568   4     |
+--------------------+--------------------+---------------------+
| 14    8      149   | 6      237     37  | 459    2457   279   |
| 2     (69)   3     | 5      78      4   | 1      78(6)  78(9) |
| 7     5      46    | 9      28      1   | (46)   2468   3     |
+--------------------+--------------------+---------------------+
UP36; 9r3c7=9r3c9-9r8c9=(9-6)r8c2=6r8c8-(6=4)r9c7 :=> -4r3c7; UP81

[Leren]

Code: Select all

*--------------------------------------------------------------------------------*
| 9       467     467      | 147     147     8        | 2       3       5        |
| 14      17      2        | 3       9       5        | 8      c47      6        |
| 5       3       8        | 47      6       2        |b49      1       79       |
|--------------------------+--------------------------+--------------------------|
| 3       47      47       | 128     15      9        | 56      2568    128      |
| 68      2       5        | 1478    147     67       | 3       9       18       |
| 68      19      19       | 28      35      36       | 7       258     4        |
|--------------------------+--------------------------+--------------------------|
| 14      8       19       | 6       237     37       |a59     d24-57   279      |
| 2       69      3        | 5       78      4        | 1       678     789      |
| 7       5       46       | 9       28      1        | 46      28      3        |
*--------------------------------------------------------------------------------*

After basics + XWing in 4's c18 r27:

H-Wing (5=9)r7c7 - (9=4)r3c7 - r2c8 = r7c8 => r7c8<5>

Leren

[Leren]

JC Van Hay wrote : UP36; 9r3c7=9r3c9-9r8c9=(9-6)r8c2=6r8c7-(6=4)r9c7 :=> -4r3c7; UP81

Looks like a typo in your move - should be ...=6r8c8...

Leren

[ArkieTech]

Code: Select all

 *-----------------------------------------------------------*
 | 9     467   467   | 147   147   8     | 2     3     5     |
 | 14    147   2     | 3     9     5     | 8    a47    6     |
 | 5     3     8     | 47    6     2     |b49    1     79    |
 |-------------------+-------------------+-------------------|
 | 3     47    47    | 128   15    9     | 56    2568  128   |
 | 68    2     5     | 1478  147   67    | 3     9     18    |
 | 68    19    19    | 28    35    36    | 7     258   4     |
 |-------------------+-------------------+-------------------|
 | 14    8     19    | 6     237   37    |c459  d257-4 279   |
 | 2     69    3     | 5     78    4     | 1     678   789   |
 | 7     5     46    | 9     28    1     | 46    28    3     |
 *-----------------------------------------------------------*
L-wing
4r2c8=(4-9)r3c7=(9-5)r7c7=5r7c8 => -4r7c8; stte

[Marty R.]

Code: Select all

+------------+-------------+--------------+
| 9  467 467 | 147  147 8  | 2   3    5   |
| 14 147 2   | 3    9   5  | 8   47   6   |
| 5  3   8   | 47   6   2  | 49  1    79  |
+------------+-------------+--------------+
| 3  47  47  | 128  15  9  | 56  2568 128 |
| 68 2   5   | 1478 147 67 | 3   9    18  |
| 68 19  19  | 28   35  36 | 7   258  4   |
+------------+-------------+--------------+
| 14 8   19  | 6    237 37 | 459 2457 279 |
| 2  69  3   | 5    78  4  | 1   678  789 |
| 7  5   46  | 9    28  1  | 46  28   3   |
+------------+-------------+--------------+


Play this puzzle online at the Daily Sudoku site

UR 47 r14c23. External analysis using candidates in box 1.

4r2c12-(4=7)r2c8-(7=9)r3c9-r3c7=r7c7-(9=1)r7c3-(1=4)r7c1
7r2c2-(7=4)r2c8-r2c1=4r7c1

Common outcome r7c1=4

[David P Bird]

Marty R, the (14)UR:r14c23 you explored is a mirage. As (6) is confined to r1c23, the UR can never be formed and so its threat won't supply any extra inferences. Similarly there is a less developed (47)UR:r15c45 that's can also be ignored because the bivalue (47)r3c4 will ensure it can't happen.

Branched logic, as you seem to have used for your deduction, is generally considered less elegant than simple chains.

As Leren alone found (4)r2c2 & (4)r7c7 can be eliminated by (4)Xwing:r27c18 in the preliminary steps, but I guess it depends on what methods are considered to be generally accepted at the start.

[Marty R.]

Marty R, the (14)UR:r14c23 you explored is a mirage. As (6) is confined to r1c23, the UR can never be formed and so its threat won't supply any extra inferences. Similarly there is a less developed (47)UR:r15c45 that's can also be ignored because the bivalue (47)r3c4 will ensure it can't happen.

Branched logic, as you seem to have used for your deduction, is generally considered less elegant than simple chains.

As Leren alone found (4)r2c2 & (4)r7c7 can be eliminated by (4)Xwing:r27c18 in the preliminary steps, but I guess it depends on what methods are considered to be generally accepted at the start.

David, thank you for your comments. I agree branched logic is less elegant, but one has to go with what one can find.

Critique of my moves is always welcome; I need all the help I can get.

[pjb]

Starting with Leren's position, I rather like the following chain which does it in one:

(1=4)r2c1 - 4r2c8 = (4-9)r3c7 = 9r7c7 - (9=1)r7c3 :=> -1r7c1

Cheers, pjb

[tlanglet]

Still another solution is

4r7c1=4r2c1-(4=7)r2c8-(7=9)r3c9-r78c9=r7c7-(9=1=4)r7c31 => r7c1=4