The New Sudoku Players' Forum

[Ocean]

This might serve as an exercise in chain application:

Code: Select all

 . . 9 | . 4 . | 7 . .
 . . . | . . . | . . .
 4 . . | 1 . 3 | . . 6
-------+-------+------
 . . 3 | 8 . 7 | 4 . .
 2 . . | . . . | . . 1
 . . 8 | 4 . 2 | 6 . .
-------+-------+------
 9 . . | 2 . 6 | . . 3
 . . . | . . . | . . .
 . . 7 | . 8 . | 5 . .

[Edit: It was not as hard as I thought. Needed one step with bilocation chains, and a later step with mixed xy-chains. So, I don't need 'help' any longer, but leaves the puzzle as an exercise.]

[keith]

I would rate any puzzle that starts with three swordfish as challenging!

Keith

[ravel]

After the 2 swordfishes:

Code: Select all

 *-----------------------------------------------------------------------------*
 | 13568   12356   9       | 56      4       58      | 7       1235    258     |
 | 135678  1356    1256    | 5679    2569    589     | 1239    13459   4589    |
 | 4       578     25      | 1       2579    3       | 289     589     6       |
 |-------------------------+-------------------------+-------------------------|
 | 156     1569    3       | 8       1569    7       | 4       259     259     |
 | 2       45679   456     | 3569    3569    59      | 389     35789   1       |
 | 157     159     8       | 4       1359    2       | 6       359     579     |
 |-------------------------+-------------------------+-------------------------|
 | 9       1458    145     | 2       57      6       | 18      1478    3       |
 | 13568   13456   12456   | 3579    359     14      | 129     1469    4789    |
 | 136     12346   7       | 39      8       14      | 5       12469   249     |
 *-----------------------------------------------------------------------------*


If r2c4=7:
r3c2=7,r7c2=8
r8c9=7,r8c1=8
=> r2c1=7

Code: Select all

 *--------------------------------------------------------------------*
 | 1356   12356  9      | 56     4      58     | 7      125    258    |
 | 7      156    56     | 569    2      589    | 13     1345   458    |
 | 4      8      25     | 1      7      3      | 29     59     6      |
 |----------------------+----------------------+----------------------|
 | 156    1569   3      | 8      19     7      | 4      259    259    |
 | 2      7      4      | 359    6      59     | 39     8      1      |
 | 15     159    8      | 4      139    2      | 6      359    7      |
 |----------------------+----------------------+----------------------|
 | 9      4      1      | 2      5      6      | 8      7      3      |
 | 8      356    256    | 7      39     14     | 129    1469   49     |
 | 36     236    7      | 39     8      14     | 5      12469  249    |
 *--------------------------------------------------------------------*


If r6c5=3:
r8c5=9
r2c8=3,r2c9=4,r8c9=9
=> r6c8=3

PS: Sorry, i have not seen before, that Ocean already posted essentially the same solution in another thread yesterday.

[Ocean]

If r2c4=7:
r3c2=7,r7c2=8
r8c9=7,r8c1=8
=> r2c1=7

If r6c5=3:
r8c5=9
r2c8=3,r2c9=4,r8c9=9
=> r6c8=3

PS: Sorry, i have not seen before, that Ocean already posted essentially the same solution in another thread yesterday.

Thank you for showing your solution. The fact that our methods are essentially the same, might indicate that this is the most natural way to solve the two hard steps.