Problem at first Hard

Advanced methods and approaches for solving Sudoku puzzles

Problem at first Hard

Postby HopDunne » Tue Jun 28, 2005 8:38 pm

can anyone help me with the next step

7*5 *1* **9
*6* 8*7 *4*
*** *** ***

938 *** 567
*** 675 ***
657 **8 421

5** *** **4
84* 5*2 *1*
3** *8* *52
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Postby Arnie » Tue Jun 28, 2005 8:42 pm

look at row 8 ...you can insert a number...
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Postby scrose » Tue Jun 28, 2005 9:02 pm

It is worth noting that this grid, as posted, does not have a solution.
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Postby Hammerite » Wed Jun 29, 2005 12:52 am

Yes, it's a funny thing how a starting grid with no obvious problems on it (duplicated numbers, etc) can in fact have no solutions... but, nevertheless...

(if you want to verify this for yourself, go to http://sudoku.sourceforge.net/ and enter the grid, then click "Evaluate". You can also click "Solve" and the program will fill in as much of the grid as possible before giving up - you can do quite a lot before you have to do that it seems...)
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Problem at first HArd

Postby Cec » Wed Jun 29, 2005 4:27 am

Arnie wrote:look at row 8 ...you can insert a number...


To "Arnie " Could you please explain where a number goes in row 8 and your logic to arrive at this?
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Postby simes » Wed Jun 29, 2005 6:45 am

cecbevwr,

There's only one cell in row 8 that can contain a 7.
Last edited by simes on Sun Dec 11, 2011 2:34 pm, edited 1 time in total.
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Re: Problem at first Hard

Postby HopDunne » Wed Jun 29, 2005 6:58 pm

HopDunne wrote:can anyone help me with the next step

7*5 *1* **9
*6* 8*7 *4*
*** *** ***

938 *** 576
*** 675 ***
657 **8 421

5** *** **4
84* 5*2 *1*
3** *8* *52
Sorry everybody,top row in block six had an error which i have now corrected(576 instead of 567)
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Postby scrose » Wed Jun 29, 2005 7:23 pm

Look at where the 4's can go in row 3.
After making some eliminations, you can fill some cells in block 5.
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Postby Arnie » Wed Jun 29, 2005 7:27 pm

cecbevwr,

simes's answer is spot on. Is that clear?

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Postby scrose » Wed Jun 29, 2005 9:01 pm

HopDunne wrote:In row 3, box 1 or 3 can only contain a 4. In row 1, box 4 or 6 and row 8 box 4 or 6, this does not help me with 124 in block 5, what do you think ?

Your terminology is a little confusing. Instead of saying "row 3, box 1 or 3", say "row 3 column 1 or row 3 column 3", or abbreviated as "r3c1 or r3c3". The term "box" usually refers to one of the 3x3 subgrids. Wayne has suggested some common terms that we should try to use to avoid confusion amongst each other.

First, to clarify, I think you meant to write row 9, not row 8.

For now, ignore all other rows: focus only on row 3 and where the 4's can go in it. You may have already noticed what I am about to explain, but just in case you haven't...

The only candidate 4's in block 1 are located in row 3. This means that the 4 that is located in row 3 must be located in block 1. That means that there cannot be any 4's in row 3 in blocks 2 or 3. So in this puzzle, you can eliminate the candidate 4's from r3c4, r3c5, and r3c6.

Having made those eliminations, where can you put a 4 in column 5?

(If interested, you can read more about the technique I used.)
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Problem at first Hard

Postby HopDunne » Wed Jun 29, 2005 9:49 pm

scrose wrote:
HopDunne wrote:In row 3, box 1 or 3 can only contain a 4. In row 1, box 4 or 6 and row 8 box 4 or 6, this does not help me with 124 in block 5, what do you think ?

Your terminology is a little confusing. Instead of saying "row 3, box 1 or 3", say "row 3 column 1 or row 3 column 3", or abbreviated as "r3c1 or r3c3". The term "box" usually refers to one of the 3x3 subgrids. Wayne has suggested some common terms that we should try to use to avoid confusion amongst each other.

First, to clarify, I think you meant to write row 9, not row 8.

For now, ignore all other rows: focus only on row 3 and where the 4's can go in it. You may have already noticed what I am about to explain, but just in case you haven't...

The only candidate 4's in block 1 are located in row 3. This means that the 4 that is located in row 3 must be located in block 1. That means that there cannot be any 4's in row 3 in blocks 2 or 3. So in this puzzle, you can eliminate the candidate 4's from r3c4, r3c5, and r3c6.

Having made those eliminations, where can you put a 4 in column 5?

(If interested, you can read more about the technique I used.)
Thanks scrose i should have seen that one, i am new to the game so i will learn the proper terminology or common terms so as not to be confusing everyone, thanks again, Slainte.
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Problem at first hard

Postby Cec » Wed Jun 29, 2005 11:43 pm

My apologies to simes, arnie, Animator. I now feel an idiot in not recognizing earlier that there's only one cell in row 8 that can contain a 7.
I'm new to this including the procedure for sending posts. Sorry again for my silly mistake.
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Postby Arnie » Thu Jun 30, 2005 10:06 am

If I apologised every time I made a mistake in Sudoku, ....!!

This forum is where you can post questions/puzzles that have you stumped/or where you fail to understand the logic in other threads. Long may that continue.

Please don't feel the need to apologise. Hope you find this forum as useful, approachable and supportive as I do.

Regards,

Arnie
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