The New Sudoku Players' Forum

[Tapestry]

Sorry my format is such a mess - not sure how to do it so that it lines up.

Here's the original puzzle:

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

Here's how far I've gotten:

+----------------------------------------+
| 6 3 18 | 57 2 57 | 4 189 89 |
| 2 7 4 | 13 9 8 | 13 6 5 |
| 5 9 18 | 34 14 6 | 38 7 2 |
|-------+-------+----------------------|
| 3 5 679 | 127 8 17 | 269 49 46 |
| 8 1 2 | 46 46 9 | 5 3 7 |
| 49 46 679 | 27 5 3 | 2689 89 1 |
|-------+-------+-----------------------|
| 7 8 56 | 9 136 2 | 16 145 346 |
| 1 2 569 | 8 36 4 | 7 59 369 |
| 49 46 3 | 156 7 15 | 1689 2 689 |
+---------------------------------------+

Thanks

[tarek]

Tapestry,

The next move according to the pencilmarks IMO is a Swordfish ........

2 links for reading:
Ultimate Fish Guide
arcilla's thread

tarek

[Glyn]

Tapestry

Firstly When you paste the puzzle into the editor box, if you select the grid and select the Code button it will add the appropriate formatting commands.



Now to the puzzle which has a Swordfish for digit 1. The three candidates you need for rows 2, 4 and 9 are restricted to columns 4, 6 and 7. When you solve the rows these columns will automatically be satisfied. The 1 in r7c7 is redundant so you can eliminate it. It's singles from here.

I've marked the Swordfish with X the eliminated candidate with -.

Code: Select all

.---------------.---------------.----------------.
| 6    3    18  | 57   2    57  | 4     189  89  |
| 2    7    4   | 1X3  9    8   | 1X3   6    5   |
| 5    9    18  | 34   14   6   | 38    7    2   |
:---------------+---------------+----------------:
| 3    5    679 | 1X27 8    1X7 | 269   49   46  |
| 8    1    2   | 46   46   9   | 5     3    7   |
| 49   46   679 | 27   5    3   | 2689  89   1   |
:---------------+---------------+----------------:
| 7    8    56  | 9    136  2   | -16   145  346 |
| 1    2    569 | 8    36   4   | 7     59   369 |
| 49   46   3   | 1X56 7    1X5 | 1X689 2    689 |
'---------------'---------------'----------------'

[Steve R]

If, like me, you find conjugates easier to spot than swordfish, you can make the same elimination using the conjugates for 1 in row 2 and column 5:

Code: Select all

.---------------.---------------.-----------------.
| 6    3    18  |  57   2    57 |  4     189  89  |
| 2    7    4   | *13   9    8  | *13    6    5   |
| 5    9    18  |  34  †14   6  |  38    7    2   |
:---------------+---------------+-----------------:
| 3    5    679 |  127  8    17 |  269   49   46  |
| 8    1    2   |  46   46   9  |  5     3    7   |
| 49   46   679 |  27   5    3  |  2689  89   1   |
:---------------+---------------+-----------------:
| 7    8    56  |  9   †136  2  | -16    145  346 |
| 1    2    569 |  8    36   4  |  7     59   369 |
| 49   46   3   |  156  7    15 |  1689  2    689 |
'---------------'---------------'-----------------'

Steve

[tarek]

If, like me, you find conjugates easier to spot than swordfish, you can make the same elimination using the conjugates for 1 in row 2 and column 5

This happens because a 2*2*2 swordfish exists, a colouring equivalent would not be there in the absence of that vaiety.

tarek

[Tapestry]

to all for their help!