Stuck on Hard puzzle - Star Ledger, NJ, Feb 27 2006 #57288

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Stuck on Hard puzzle - Star Ledger, NJ, Feb 27 2006 #57288

Postby NoahsMyBro » Fri Mar 03, 2006 3:47 am

Code: Select all
. . 5 | 7 . 2 | . 8 .       . . 5 | 7 3 2 | . 8 .
8 . . | . 9 . | . . .       8 7 . | . 9 . | . . .
. 9 2 | . . . | . . .       . 9 2 | . 8 . | . . .
- - - + - - - + - - -       - - - + - - - + - - -
. . . | . . 3 | . . 4       . . 8 | 9 7 3 | . 5 4
7 4 . | . . . | . 9 6       7 4 . | . . . | . 9 6
5 . . | 1 . . | . . .       5 . 9 | 1 6 4 | . . .
- - - + - - - + - - -       - - - + - - - + - - -
. . . | . . . | 7 1 .       . . . | . . . | 7 1 .
. . . | . 4 . | . . 2       . . . | . 4 7 | . 6 2
. 8 . | 6 . 9 | 5 . .       2 8 7 | 6 1 9 | 5 4 3

AS PRINTED IN PAPER.        WITH MY ANSWERS SO FAR.


I've been wracking my brains on this puzzle since Monday evening. The above is the original, as printed in the paper, and with my answers so far.

I've determined the following:
* In box 2: r2c4 & r3c4 are the pair of 4 & 5. r2c6 & r3c6 are the pair of 1 & 6.
* In box 3: Either r1c7 or r1c9 is 9.
* Column 6: Row 2 & 3 share the pair of 1 & 6; Row 5 & Row 7 share the pair of 5 & 8.

There's a bunch of other, pretty obvious facts as well, but I'm sure you guys can see them for yourself.

I haven't been able to determine any more definite placements though. I'd prefer not to just look at the answers, however. But at this point I've spent way too much time on this particular puzzle (to the detriment of wife and work), and I've got to ask for a hint, if any of you can nudge me in the right direction.

Thanks,
Steve
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Postby vidarino » Fri Mar 03, 2006 8:47 am

You should have a pair of 1 and 3 in column 3. That will leave just a single spot for a 3 in one of the boxes.:)
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Re: Stuck on Hard puzzle - Star Ledger, NJ, Feb 27 2006 #57

Postby Cec » Fri Mar 03, 2006 11:48 am

in Hi Steve,

I don't know if you have read up the recommended procedures for submitting puzzles and terminology which are set out in the following (click on this) THREAD. The original puzzle and the stage you reached, including the pencilmarks (candidates), would look like this. I've deleted the pencilmark grid for the original puzzle merely to save space. As you can see it's then easier, both to yourself and readers, to look for hints to start eliminating pencilmarks.
Code: Select all
 *-----------*
 |..5|7.2|.8.|
 |8..|.9.|...|
 |.92|...|...|
 |---+---+---|
 |...|..3|..4|
 |74.|...|.96|
 |5..|1..|...|
 |---+---+---|
 |...|...|71.|
 |...|.4.|..2|
 |.8.|6.9|5..|
 *-----------*

 *-----------*
 |..5|732|.8.|
 |87.|.9.|...|
 |.92|.8.|...|
 |---+---+---|
 |..8|973|.54|
 |74.|...|.96|
 |5.9|164|...|
 |---+---+---|
 |...|...|71.|
 |...|.47|.62|
 |287|619|543|
 *-----------*

 *--------------------------------------------------------------------*
 | 146    16     5      | 7      3      2      | 1469   8      19     |
 | 8      7      346    | 45     9      16     | 12346  23     15     |
 | 1346   9      2      | 45     8      16     | 1346   37     157    |
 |----------------------+----------------------+----------------------|
 | 16     126    8      | 9      7      3      | 12     5      4      |
 | 7      4      13     | 258    25     58     | 1238   9      6      |
 | 5      23     9      | 1      6      4      | 238    237    78     |
 |----------------------+----------------------+----------------------|
 | 3469   356    346    | 2358   25     58     | 7      1      89     |
 | 139    135    13     | 358    4      7      | 89     6      2      |
 | 2      8      7      | 6      1      9      | 5      4      3      |
 *--------------------------------------------------------------------*

Looking at the pencilmark grid you will see the [13] pair in column3 that Vidar mentioned. This is known as a "naked pair" - two numbers in two cells by themselves, which means you can exclude any other 1's and 3's from other cells in this same group (row, column or box). This leads to a "hidden" single 3 being left in one of these 'boxes'. Boxes are the nine 3X3 grids, box1 is the top left corner grid, box5 is the centre grid and box9 the lower right corner grid.

You can also have "naked triples" which is three numbers or a combination of those three numbers occupying only three cells in a group with no other candidates in those three cells. An example of this is the [258] numbers exclusively in three cells in row5 (box 5). This triple means candidates 2 and 8 can be excluded from other cells in this row (cell r5c7). The rest of the puzzle can be solved mainly by spotting 'hidden' singles - only one cell in a group where a candidate can go.

If you haven't yet looked at the following sites, they explain many of the solving techniques, ranging from basic to advanced.
http://www.angusj.com/sudoku/hints.php
http://www.simes.clara.co.uk/programs/sudokutechniques.htm

I hope this helps rather than interfere too much with your work:):)

Cec
Last edited by Cec on Fri Mar 03, 2006 8:22 am, edited 1 time in total.
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Postby tarek » Fri Mar 03, 2006 12:11 pm

hi NoahsMyBro,

There is no way of saying where you actually reached........

The pencilmarks will give us an idea of your solving techniques.....

now,

although the naked double "13" ultimately solves it,, did you manage to spot some box-line (locked candidate) eliminations before that ??

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"Star Ledger,NJ,Feb 27 2006#57288

Postby Cec » Fri Mar 03, 2006 12:34 pm

tarek wrote:hi NoahsMyBro,
"There is no way of saying where you actually reached..."

Unless I'm missing something Tarek doesn't Steve's second grid show the stage he reached?.
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Re: "Star Ledger,NJ,Feb 27 2006#57288

Postby vidarino » Fri Mar 03, 2006 1:08 pm

cecbevwr wrote:
tarek wrote:hi NoahsMyBro,
"There is no way of saying where you actually reached..."

Unless I'm missing something Tarek doesn't Steve's second grid show the stage he reached?.
Cec


Only partially. It doesn't show if he has made any eliminations (that haven't yielded the placement of a number) yet.
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Postby MCC » Fri Mar 03, 2006 1:12 pm

Cec I believe Tarek was talking about candidate elimination.
NoahsMyBro my have made further eliminations candidate wise than the grid which he'd posted would show. Does that make sense?

In addition to what's be said, 5's are locked candidates in box2 column 4 so any other 5's in c4 can be eliminated.

A x-wing in 5's
r5c56 and r7c56
Allows you to eliminate the 5 in r7c2

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Re: "Star Ledger,NJ,Feb 27 2006#57288

Postby tarek » Fri Mar 03, 2006 1:13 pm

cecbevwr wrote:Unless I'm missing something Tarek doesn't Steve's second grid show the stage he reached?


[Edited, The question was actually to me:D ]

here is steve's 2nd grid:
Code: Select all
 . . 5 | 7 3 2 | . 8 . 
 8 7 . | . 9 . | . . . 
 . 9 2 | . 8 . | . . . 
-------+-------+------
 . . 8 | 9 7 3 | . 5 4 
 7 4 . | . . . | . 9 6 
 5 . 9 | 1 6 4 | . . . 
-------+-------+------
 . . . | . . . | 7 1 . 
 . . . | . 4 7 | . 6 2 
 2 8 7 | 6 1 9 | 5 4 3


which one of the following reflects where did he reach:

Code: Select all
#1
*-----------------------------------------------------------------*
| 146    16     5     | 7      3      2     | 1469   8      19    |
| 8      7      1346  | 45     9      156   | 12346  23     15    |
| 1346   9      2     | 45     8      156   | 1346   37     157   |
|---------------------+---------------------+---------------------|
| 16     126    8     | 9      7      3     | 12     5      4     |
| 7      4      13    | 258    25     58    | 1238   9      6     |
| 5      23     9     | 1      6      4     | 238    237    78    |
|---------------------+---------------------+---------------------|
| 3469   356    346   | 2358   25     58    | 7      1      89    |
| 139    135    13    | 358    4      7     | 89     6      2     |
| 2      8      7     | 6      1      9     | 5      4      3     |
*-----------------------------------------------------------------*

#2
*--------------------------------------------------------*
| 146   16    5    | 7     3     2    | 469   8     19   |
| 8     7     1346 | 45    9     156  | 2346  23    15   |
| 1346  9     2    | 45    8     156  | 346   37    157  |
|------------------+------------------+------------------|
| 16    126   8    | 9     7     3    | 12    5     4    |
| 7     4     13   | 258   25    58   | 13    9     6    |
| 5     23    9    | 1     6     4    | 238   237   78   |
|------------------+------------------+------------------|
| 3469  356   346  | 2358  25    58   | 7     1     89   |
| 139   135   13   | 358   4     7    | 89    6     2    |
| 2     8     7    | 6     1     9    | 5     4     3    |
*--------------------------------------------------------*

#3
*--------------------------------------------------------*
| 146   16    5    | 7     3     2    | 469   8     19   |
| 8     7     46   | 45    9     156  | 2346  23    15   |
| 1346  9     2    | 45    8     156  | 346   37    157  |
|------------------+------------------+------------------|
| 16    126   8    | 9     7     3    | 12    5     4    |
| 7     4     13   | 258   25    58   | 13    9     6    |
| 5     23    9    | 1     6     4    | 238   237   78   |
|------------------+------------------+------------------|
| 3469  356   46   | 2358  25    58   | 7     1     89   |
| 139   135   13   | 358   4     7    | 89    6     2    |
| 2     8     7    | 6     1     9    | 5     4     3    |
*--------------------------------------------------------*


#1: you can do some box-line eliminations
#2: you need the double
#3: you need a hidden single

That is why we ask for the actual pencilmarks cec.


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Postby NoahsMyBro » Fri Mar 03, 2006 2:48 pm

Wow - thanks for all of the replies.

I can't really look at all of this now, but will definitely give it some attention tonight.

But, briefly:
I didn't originally post the pencilmarks out of laziness; I just didn't want to type the grid a third time. From now on I'll do better.

Late last night I tried to figure out how vidarino could conclude that the two cells in column 3 were only 1 and 3. I didn't figure it out yet, but it was something like 2 or 3am, so I plan on attempting it again before coming back here for more help.

When I return, I'll post with my pencilmarks, and look at the suggestions you guys have offered.

Thanks,
Steve
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Re: "Star Ledger,NJ,Feb 27 2006#57288

Postby Cec » Fri Mar 03, 2006 3:18 pm

Thanks Tarek and MCC for replying. Both your explanations and posted grids make sense that the candidate grid will progressively change with progressive elimination of candidates without adding a new "Big number (clue) to the grid. I "checked" Steve's first grid to make sure it correctly proceeded to his second submitted grid which it did. I then progressed from there to explain a couple of techniques to help Steve try and continue solo with the techniques described in the links suggested.

I'm probably entering into a different topic by raising my next point but I'm never really sure how much help to offer for "first time posters"- this being a typical situation - where the poster's skill level is obviously unfamiliar to me. It's hard to strike a balance between giving too much - which at times I think I might be doing - or only giving say one hint and suspecting one hint isn't going to get 'them' very far, if that makes sense. I suppose we do what we think we need to do and just hope it will be satisfactory. Just thought I'd mention this 'cause it's been on my mind for a while.

Cec
PS. It's now 1.30am, crickey! this is getting serious:) Just noticed that Steve has obviously appreciated the posts but he mentions about the time involved if he had to type up a third grid. Loading puzzles into Solvers, such as SS, greatly reduces this work with no typing involved and am happy to explain this to Steve if he wants this. Now off to bed!:(
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Postby NoahsMyBro » Tue Mar 07, 2006 4:30 pm

I wanted to return and post an update for you all, so you didn't think I blew you off.

Over the last week I've been very busy with work, so I never had a chance to try out the suggestions you offered, or to jot down the pencilmarks I'd had in my head while working on the puzzle.

Last night, on the train home, I solved the puzzle, though!:D

So all's good. Of course, it took me 3 nights in a row staring at it in the paper, and then another 98 minutes on my little handheld electronic Sudoku, but it's finally solved. (I couldn't tell you how I figured it out, though. And I never figured out how to know there was a 1 & a 3 in the third column as somebody hinted above, so I couldn't use that hint.)

Thanks for the help,
Steve
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