dailysudoku.com

Danny

Resist the temptation!

All the graves I have seen, whether universal or light, bi- or multi-valent, share two characteristics. They imply that the pattern has no solution or gives rise to ...

I think http://www.sudopedia.org/wiki/Law_of_Leftovers sets out pretty much all there is to the logic.

Steve

Hi, unitron.

The puzzle has just one solution but to find it you need to watch out for a pair at the bottom of the second column.

Steve

You can place 3 in r8c2 using the contradiction:

r8c2 ≠3 => r8c1 = 3 => r4c1 ≠ 3 => r4c6 = 3 => r4c3 =1 => r5c2 =7 => r9c2 = 1 => r6c2 =5 => r8c2 = 3.

This gi ...

MM

It’s of minimal interest but, for what it’s worth, I also got straight to Leo’s grid in the very first post with its conjugates for 2 in column 7.

Steve

Kathy’s neat W-wing does the trick all on its own.

Steve

*----------------------------------------------------------------*
| 1 5 6 | 9 3 4 | 7 8 2 |
| 2 3 79 | 78 1 678 | 5 4 ...

Keith’s grid may be written as:

+----------------+------------------+----------------+
| 8 5 6 | 24 14 9 | 7 3 12 |
| 7 2 1 | 3 6 8 | 5 4 9 ...

It's usually called "box-line interaction," just as in classical SuDoku.

Steve

I think I can.

If you run your eye along row 5 you will find it intersects five boxes. Let’s call them A, B, C, D and E from left to right.

Now, your diagram makes it clear that 1 occupies row 5 ...

The puzzle can also be solved using the swordfish for 9 in rows 2, 4 and 7:

*-----------------------------------------------------------*
| 67 67 29 | 4 19 8 | 5 3 ...

In traditional style the implication snippet would be:

r4c9 ≠ 6 => r78c9 = (16) => r8c2 = 4

This looks OK to me.

Steve

It’s good to hear from you, rihiter

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

Nice to hear from you, mieblanc!

As to a hint: there is only one place for E in box 15.

Best wishes

Steve

Ted, I think you may have overlooked a W-Wing.

+-------------------------------------+
| 459 579 1 | 6 47 2 | 3 89 78 |
| 349 279 346 | 48 5 78 | 24 19 167 |
| 8 27 46 | 3 9 1 | ...

At this stage

+------------------------------------------------+
| 3 4 7 | 159 6 8 | 19 2 15 |
| 58 1 9 | 2 4 †35 | 7 †38 6 |
| 6 2 58 | 1359 *13 ...

Keith referred to an XYZ-wing 56-9.

I suspect this is pivoted on r3c9 and does the trick.

Steve

+----------+--------------+----------------+
| 6 9 4 | 5 23 7 | 28 238 1 |
| 12 12 3 | 8 46 9 | 5 46 7 |
| 5 8 7 | 36 1 2346 | 26 9 2346 |
+----------+ ...

crunched

That’s the flightless wing. To take off, check the possibilities for 2 in rows 4 and 9.

Steve

The grid is riddled with a bewildering number of deadly patterns so it’s easy to miss the most helpful.

To avoid a (567) in r456c19, 2 must be placed in r4c1 and singles follow.

Steve