The New Sudoku Players' Forum

[gurgi]

I am really stumped. Help!

56 7 356 | 1 9 258 | 3568 2568 4
569 8 3569 | 7 4 25 | 356 1 236
14 14 2 | 6 58 3 | 7 9 58
______________________________________________________

2569 259 569 | 8 7 56 | 4 3 1
3 1459 14569 | 249 25 456 | 5689 2568 7
7 459 8 | 2349 235 1 | 569 256 269
______________________________________________________

149 6 1479 | 5 138 48 | 2 47 39
1245 3 1457 | 24 6 9 | 158 4578 58
8 12459 1459 | 234 123 7 | 13569 456 369

[TKiel]

gurgi,

Box-line interaction, naked triple/hidden pair, another box-line interaction. Then all singles. Most of the action takes place in box 4 (left middle) and column 2. Hope this is enough info but not more that you want/need.

Tracy

[gurgi]

If there is a naked triple in this puzzle (and I believe you) I am at a loss to find it. Ditto with a hidden pair. Can you give me a few more clues?

[TKiel]

Gurgi,

You need to find the box-line interaction in box 4 first. Look at where the 9's in row 4 are. The exclusions from that create the naked triple/hidden pair.

Tracy

[gurgi]

Tracy,

You are teaching me something new here, which I really appreciate. But I don't seem to be an apt pupil. When I look at the 4s and 9s in both box 4 and row 4, I can't find anything that I've ever used before. Box 4 has 9's in every unsolved square, making anything with 4-9 unworkable. Row 4, column 7 gets an 8 with a 9 which seems to muck the whole thing up as far as doing anything with 4's and 9's in the row. Can you be even more specific? I might be able to get farther in this book if I can learn your approach here.

Thanks. Kate

[Cec]

Hi Kate, I hope Tracy doesn't mind me helping out.

Your grid looks like this:

Code: Select all

 *--------------------------------------------------------------------*
 | 56     7      356    | 1      9      258    | 3568   2568   4      |
 | 569    8      3569   | 7      4      25     | 356    1      236    |
 | 14     14     2      | 6      58     3      | 7      9      58     |
 |----------------------+----------------------+----------------------|
 | 2569   259    569    | 8      7      56     | 4      3      1      |
 | 3      1459   14569  | 249    25     456    | 5689   2568   7      |
 | 7      459    8      | 2349   235    1      | 569    256    269    |
 |----------------------+----------------------+----------------------|
 | 149    6      1479   | 5      138    48     | 2      47     39     |
 | 1245   3      1457   | 24     6      9      | 158    4578   58     |
 | 8      12459  1459   | 234    123    7      | 13569  456    369    |
 *--------------------------------------------------------------------*


Look at row4 (r4). Notice the only 9's in that row occur in Box4 (the middle left 3X3 box). This means the 9 in box4 must be in either the cells row4 column1 (r4c1) or r4c2 or r4c3. Therefore all other 9's in the rest of box4 can be eliminated. With these exclusions, you will see that c2 now has a naked triple [14] [145] and [45] occupying just three cells. This now means all other candidates[145] in this same column2 can be excluded.

Look at Box6 and r6 and try seeing why other 6's can be excluded from Box6. Also look at c2 and Box 4 again. Note the 5's only in c2 which means further exclusions of 5's in this Box.

For solving techniques click on these links:

http://www.angusj.com/sudoku/hints.php
http://www.sadmansoftware.com/sudoku/techniques.htm
http://www.scanraid.com/BasicStrategies.htm

Post if you are still stuck.

Cec

[gurgi]

Cec and Tracy:

Argggghhhh.

Plain as the nose on my face. Couldn't see the forest for the trees, or in this case trees for the forest.

Totally embarrassed, and in your debt. I'll solder on.

[TKiel]

Couldn't see the forest for the trees, or in this case trees for the forest.

Happens to all of us at one time or another. Sort of reminds me of the time I used multi-colouring to answer a poster's question because I didn't see the naked pair. If it's any consolation, IMO that is the hardest kind of box-line interaction to spot. Do soldier on, it will only get easier. (Until you get to forcing chains, anyway.)

I hope Tracy doesn't mind me helping out.

Of course not, always glad for the assistance. As usual, you've managed to explain it as well as or better than I did. So I should say that I assisted you in the explanation and not the other way around.

Tracy

[Cec]

Thanks for the feedback Kate. It's always nice to know the help offered was both understood and appreciated. Also Tracy has helped me out a lot in explaining some techniques i didn't understand - so we all help one another

Cec

[Pat]

Frank Longo Black Belt

Code: Select all

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

seems a decent puzzle at the level of Pappocom's Hard puzzles - is the rest of the book at the same level?


there are many SuDoku titles by Frank Longo,
including:

• Second-Degree Black Belt Sudoku
  
• Martial Arts Sudoku Level 9: Black Belt Sudoku
  
  

~ Pat