The New Sudoku Players' Forum

[mayres]

*-----------*
|4..|..7|3..|
|..3|..6|..4|
|.8.|431|...|
|---+---+---|
|.1.|..8|.46|
|.64|.1.|85.|
|798|564|123|
|---+---+---|
|.3.|645|.7.|
|...|1..|4..|
|.49|87.|..1|
*-----------*
I apologize if I have posted in the wrong place - I am still in the early stages of learning some of the principles of solving and cannot figure the logic for the next move at this stage of this particular puzzle. Can someone please tell me which cell you would put a number in next and what is the logic for that selection? THANKS! mike

[daj95376]

Code: Select all

# You've done all you can with assigning Singles
# Now, it's time to learn about elimination techniques
# I would suggest the Naked Pair <29> in (column 4) and (box 2)
 *--------------------------------------------------------------------*
 | 4      25     1256   |*29     58-29  7      | 3      1689   2589   |
 | 1259   257    3      |*29     58-29  6      | 2579   189    4      |
 | 2569   8      2567   | 4      3      1      | 25679  69     2579   |
 |----------------------+----------------------+----------------------|
 | 235    1      25     | 37-29  29     8      | 79     4      6      |
 | 23     6      4      | 37-29  1      239    | 8      5      79     |
 | 7      9      8      | 5      6      4      | 1      2      3      |
 |----------------------+----------------------+----------------------|
 | 128    3      12     | 6      4      5      | 29     7      289    |
 | 2568   257    2567   | 1      29     239    | 4      3689   2589   |
 | 256    4      9      | 8      7      23     | 256    36     1      |
 *--------------------------------------------------------------------*


[mayres]

Thank you for the reply. I actually had used that technique to get to the part where my puzzle looked like the following one. I should have written it in this form the first time but I obviously didn't know how to quickly jot my sample down in text form as you have shown - in fact I don't know if mine will be as good as yours even now. Can you tell me what the next step of logic from THIS point might be?
*--------------------------------------------------------------------*
| 4 25 1256 |29 58 7 | 3 1689 2589 |
| 1259 257 3 |29 58 6 | 2579 189 4 |
| 2569 8 2567 | 4 3 1 | 25679 269 2579 |
|----------------------+----------------------+----------------------|
| 235 1 25 | 37 29 8 | 79 4 6 |
| 23 6 4 | 37 1 29 | 8 5 79 |
| 7 9 8 | 5 6 4 | 1 2 3 |
|----------------------+----------------------+----------------------|
| 128 3 12 | 6 4 5 | 29 7 289 |
| 2568 257 2567 | 1 29 239 | 4 2368 258 |
| 256 4 9 | 8 7 23 | 256 36 1 |
*--------------------------------------------------------------------*

If it would be any easier I could email the puzzle in excel format and we could discuss via email OR continuing via the forum format is just fine too if that is preferred? I'm (again) searching for anyone who can help me learn a few principles that will take me to the next level by pointing out the logic to get beyond a few stuck points. I appreciate your comments and thank your again for responding. mike

[ronk]

Can you tell me what the next step of logic from THIS point might be?

You can get hints from freeware programs. I don't hesitate to recommend Angus Johnson's Simple Sudoku which can be downloaded (sudoku_setup.exe) from here. The page also contains a link to a helpful step-by-step guide.

[edit: correct typo]

[Steve R]

You will find two pairs helpful. The first, (16) in the first row, leads immediately to the second, (19) in the second row.

Steve

[mayres]

Steve - can you explain what you mean by this? r1c8 has 1689 and right below in r2c8 is 189. What does this do for me? Sorry to be a little slow in understanding the hints. Thanks - mikr

[Steve R]

You gave your first row as:

Code: Select all

4 25 1256 |29 58 7 | 3 1689 2589

Only two cells are open to 1 and 6, so they must contain these entries: all other candidates may be eliminated from them. This makes the first row:

Code: Select all

4 25 16 |29 58 7 | 3 16 2589

If you now look at boxes 6 and 9, you will see that that neither can have 9 placed in the eighth column, which means that it must be in the eighth column in box 3. In particular r1c9 does not contain 9 and only one cell is left for it in the first row.

Steve

[mayres]

Steve - THANK YOU THANK YOU - I actually understood all the logic you explained very clearly. This was the first time I have ever seen the two pairs removed from other strings of numbers like you did in row 1 to get the two 16's. I will try to build on this.
Thanks again - blessings, Mike

[Cec]

"....but I obviously didn't know how to quickly jot my sample down in text form as you have shown - in fact I don't know if mine will be as good as yours even now..."

Hi Mike,
I haven't posted in for a while so my attempt may be a bit rusty to help you post puzzles in a format similar to daj95376 above post . You should enclose your puzzle between the "Code" tags which appear in the "Message body" of the "Post a reply" window. In the following explanation I have used parenthesis brackets { } to show how it looks but you must use the correct [ ] brackets.

{Code} Your puzzle inserted here {/Code}.. When I use the correct [ ] brackets then it would look like this:

Code: Select all

 Your puzzle inserted here

My apologies to udosuk who posted a simpler explanation of this some time back but I couldn't remember the particular thread.

In addition to the excellent Angus Johnson link suggested above by Ronk you may also find the following link useful:

http://www.scanraid.com/BasicStrategies.htm

Cec

[udosuk]

My apologies to udosuk who posted a simpler explanation of this some time back but I couldn't remember the particular thread.

No need to apologize. Here is the thread:

http://forum.enjoysudoku.com/viewtopic.php?t=5405

Been away for awhile, just catching up at the moment...

[Cec]

"...No need to apologize. Here is the thread:

Thanks udosuk for your reply. However, this wasn't the thread I was thinking of, which, from memory, showed where the correct code brackets thus

Code: Select all

 and

should be placed rather than using the synthesis brackets { }. I think you did this by using a white colour or zero size font so that the reader understood your explanation rather than produce the confusing quotation "and" which now appears in this thread. I suspect I'm making a mess with this explanation and I can't overlook the possibility that the author of the "mystery" thread may have originated from another member.

Cec

[udosuk]

Let's try these 2 threads:

http://forum.enjoysudoku.com/viewtopic.php?t=5346

http://forum.enjoysudoku.com/viewtopic.php?t=3981

[Cec]

Thanks again udosuk. Your above second thread, courtesy of Ruud, viz.
http://forum.enjoysudoku.com/viewtopic.php?t=3981 seems to be the "nifty trick" I remembered though my memory failed badly as to how it was done..

Using Ruud's technique, explaining how a puzzle is enclosed between the code tags without them being interpreted as BBCode, makes [code[b][/b]]text[/code[b][/b]] look like [code] text [/code]

Cec

[Steve48]

Steve - THANK YOU THANK YOU - I actually understood all the logic you explained very clearly. This was the first time I have ever seen the two pairs removed from other strings of numbers like you did in row 1 to get the two 16's.

Mike, in case you're interested, the situation that Steve R pointed out to you is called a "hidden pair". There's another way of looking at it that leads to the same result. In that same row, cells 2, 4, 5, and 9 contain 25, 29, 58, and 2589 respectively. The four digits 2, 5, 8, and 9, and only those four digits, are candidates for those four cells, and therefore must occupy those cells. This is called a "naked quad", and it means that those four digits can be eliminated from every other cell. Eliminating them from cells 3 and 8 leaves only 1 and 6 as candidates in those cells, just as before.

You'll find this sort of complementary situation often in Sudoku. I find that I can spot a naked triple or naked quad more easily than I can spot a hidden pair, but maybe that's just me.