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March 4, 2006, hard puzzle

 
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David
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PostPosted: Sun Mar 05, 2006 10:11 pm    Post subject: March 4, 2006, hard puzzle Reply with quote

On March 4 hard puzzle in the top left box, why does the second blank from the top in the third column from the left have to be a 2. As I am trying to work it, I can see that this blank OR the second blank down in the second column from the left must be a 2. However, I can't find a reason to eliminate either one at this point.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Sun Mar 05, 2006 10:31 pm    Post subject: March 4, 2006, hard puzzle Reply with quote

David

It is difficult to be helpful without seeing the position you have reached (and, ideally, the original puzzle as well).

My best guess at present is that you have overlooked the pair (18) in r16c3. Allowing for those entries r2c3 is the only place left for 2 in column 3.

Steve
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David
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PostPosted: Mon Mar 06, 2006 2:54 am    Post subject: March 4, 2006 hard puzzle Reply with quote

Steve, thanks for the response. I'm new to sudokus overall and especially to the hard ones.

In what I would label Row 6 (r6)--the sixth row from the top, I have established the possibility of either a 1 or 8 in Column 3 (c3) and in Column 5 (5c). So if r6c3 is an 8, then r6c5 is a 1. If r6c3 is a 1, r6c5 is the 8. I think the 1-8 pair may be what you refer to in your message as 18.

Does having the 1 or 8 choice in r6c3 determine that r2c3 must be the 2 for Column 3? I still don't see it.

Right now, I have about 20 of 54 blanks in the puzzle completed.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Mon Mar 06, 2006 2:19 pm    Post subject: March 4, 2006 hard puzzle Reply with quote

You have the notation right. By convention the rows are denoted r1, r2, …, r9, counting from top to bottom and the columns c1, c2, …, c9, counting from left to right. The boxes are b1, b2 and b3 from left to right across the top stack, b4, b5 and b6 from left to right across the middle stack etc.

When I said there was a pair (18) in r16c3, the meaning was: “the entries 1 and 8 occupy cells r1c3 and r6c3 in one or the other order.” This means that neither 1 nor 8 is available for r2c3. My grid at that time was:
Code:

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

Excluding 1 and 8 from r2c3 leaves only 2 available.

Steve
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David
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PostPosted: Tue Mar 07, 2006 1:17 am    Post subject: Following up help on March 4 puzzle Reply with quote

Thanks again, Steve. I think I just caught a glimpse of, for me, a new tool for eliminating blanks using the pairs concept to "semi-define" two blanks in a column or row especially.

What's the trick with being able to copy and send your sudoku puzzle grid as you did?

Thanks. Have a good week over there.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Tue Mar 07, 2006 3:10 am    Post subject: Reply with quote

As far as pairs are concerned, bear in mind that you will come across triples and quadruples too.

As to posting grids, and assuming you have a word processing program, one approach is to copy a grid from this site, paste it into a document and delete the entries. The resulting template can then be used to type in your own entries. When you come to inserting the result in your message, click the “Code” button, copy and paste, then click the “Code” button again. One crucial point: you have to use a Courier (fixed-pitch font family) font to preserve the structure of the grid.

I suspect that there are programs which can accept a copy of a grid in picture form, read it and produce the typewritten version automatically but I am getting well out of my depth now. If you hear of one, please let me know.

Good luck!

Steve
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David
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PostPosted: Thu Mar 09, 2006 2:44 am    Post subject: March 4 puzzle and follow up Reply with quote

Thanks for the direction and help overall, Steve.
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