Stuck again - need next step

Advanced methods and approaches for solving Sudoku puzzles

Stuck again - need next step

Postby Shazbot » Sat Oct 22, 2005 12:14 pm

Another V.Hard - maybe I'm biting off more than I can chew here....

Can someone help me just enough to get me moving again please? Not after the full solution. Thanks.

Code: Select all
GRID:

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


CANDIDATES:

[1]   [4578] [457]   | [568] [2]    [5689] | [4579]  [459]   [3]   
[6]   [2578] [3]     | [58]  [89]   [4]    | [12579] [1259]  [57] 
[9]   [245]  [245]   | [7]   [1]    [3]    | [8]     [245]   [6]   
---------------------+---------------------+-----------------------
[28]  [246]  [2469]  | [1]   [489]  [256]  | [3]     [7]     [458]
[5]   [1]    [479]   | [48]  [3]    [789]  | [49]    [6]     [2]   
[278] [3]    [24679] | [256] [4789] [256]  | [1459]  [14589] [458]
---------------------+---------------------+-----------------------
[237] [267]  [8]     | [234] [5]    [1]    | [2467]  [234]   [9]   
[237] [2567] [2567]  | [9]   [478]  [278]  | [2467]  [2348]  [1]   
[4]   [9]    [1]     | [238] [6]    [278]  | [257]   [2358]  [578]
Shazbot
 
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Postby SteveF » Sat Oct 22, 2005 12:46 pm

There is another locked candidates situation.

Where can the 4's go in column 9? This should allow some eliminations and a placement in box 6.
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Re: Stuck again - need next step

Postby QBasicMac » Sat Oct 22, 2005 3:33 pm

shazbot wrote:maybe I'm biting off more than I can chew here....


Heh - happens to me a lot.

Since the only occurrences of 4 in column 9 are in box 6, there can be no other 4's there. Eliminating 4 from those gives r5c7=9.

Unfortunately, it looks like that is the end of the easy stuff! My guess is that we are looking for hidden triples or even more advanced techniques.

Mac
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Re: Stuck again - need next step

Postby simes » Sat Oct 22, 2005 3:59 pm

edit: Deleted, because it was just plain wrong!

S
Last edited by simes on Sat Oct 22, 2005 6:08 pm, edited 1 time in total.
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Re: Stuck again - need next step

Postby QBasicMac » Sat Oct 22, 2005 8:07 pm

simes wrote:One hidden single, then just naked singles.


Mind pointing out exactly where the "hidden single" you refer to is?

Thanks

Mac

Solution So Far
Code: Select all
1-- -2- --3
6-3 --4 ---
9-- 713 8-6
--- 1-- 37-
51- -3- 962
-3- --- ---
--8 -51 --9
--- 9-- --1
491 -6- ---


Pencilmarks So Far
Code: Select all
-         4578      457       568       -         5689      457       459       -       
-         2578      -         58        89        -         1257      1259      57       
-         245       245       -         -         -         -         245       -       
28        246       2469      -         489       25689     -         -         458     
-         -         47        48        -         78        -         -         -       
278       -         24679     24568     4789      256789    15        158       458     
237       267       -         234       -         -         2467      234       -       
237       2567      2567      -         478       278       2467      2348      -       
-         -         -         238       -         278       257       2358      578     
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Postby Nick67 » Sat Oct 22, 2005 9:48 pm

Hi QBasicMac,

Here are 2 quick hints from Simple Sudoku:

1) The 8's in row 5 are locked in box 5.
2) Check out column 6: I think you'll spot something there.

You are pretty close to the avalanche of singles.
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Re: Stuck again - need next step

Postby simes » Sat Oct 22, 2005 10:07 pm

QBasicMac wrote:
simes wrote:One hidden single, then just naked singles.


Mind pointing out exactly where the "hidden single" you refer to is?

errr... it looks like I answered using the wrong grid... again.:(

My Apologies.

S
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Postby Shazbot » Sun Oct 23, 2005 12:41 am

thanks gang - sometimes I feel I just look at these things too long.


Do I now get the "can't see it unless it hits me in the face" award?
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Postby QBasicMac » Sun Oct 23, 2005 1:58 am

shazbot wrote:Do I now get the "can't see it unless it hits me in the face" award?


No way! I OWN that award!

simes wrote:it looks like I answered using the wrong grid


Whew! I'm just glad you didn't find one, proving I am blind.

Nick67 wrote:Check out column 6: I think you'll spot something there


I finally found what you were talking about. I would have preferred
this:

"r1c6, r4c6 and r6c6 contain the only occurrences of 5, 6 and 9. Therefore the other candidates in those cells can be erased"

But I have gone through all that before and admit it was my fault not to request exact, specific answers. I hate hints. When I reach the point I am stuck, I want the answer. I get no joy whatsoever out of struggling after I once give up.

That aside, I wish you a lot of grass! I can sleep now.

Mac
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Postby robertsetiadi » Mon Oct 24, 2005 6:02 am

[1,8,7,6,2,9,4,5,3]
[6,2,3,5,8,4,1,9,7]
[9,4,5,7,1,3,8,2,6]
[8,6,2,1,9,5,3,7,4]
[5,1,4,8,3,7,9,6,2]
[7,3,9,2,4,6,5,1,8]
[2,7,8,4,5,1,6,3,9]
[3,5,6,9,7,8,2,4,1]
[4,9,1,3,6,2,7,8,5]
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Postby QBasicMac » Mon Oct 24, 2005 11:52 am

Err, robertsetiadi

For your information, you are just wasting forum space by merely entering solutions. Any programmer can write a quickie program to solve SuDoku puzzles and there are some nice ones already coded and posted on the internet. Even if you solve it yourself with no computer, so what?

The forum is to discuss HOW a given puzzle can be solved, using techniques other than guessing or automatic computer solutions. The solution itself is boring and non-instructive. Nobody here has ever requested a solution.

Mac
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Postby stuartn » Mon Oct 24, 2005 12:10 pm

Hear Hear QB. - Robertsetiadi - could you tell us HOW you did it please - your techniques for dealing with locked cells - disjoint subsets etc? It'd be most helpful in future.

BTW - Nobody on the forum is the least bit interested in postings of completed grids - unless they are a valid part of a discussion concerning technique - Anybody can paste a copy of a grid from one of the multitude of solvers - so please - no more.

stuartn
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