Help please

Advanced methods and approaches for solving Sudoku puzzles

Help please

Postby jakeinprogress » Wed Jun 22, 2005 5:54 am

I'm very new to this and don't really know anyone else who is familiar with Sudoku. I'm trying to learn through experience and have been solving puzzles from the following site:

It is claimed that all puzzles at the above site are solvable through logic alone and do not require trial and error (I won't wade into that dispute). After solving several, I got stuck on one and asked for a hint (after using the drawer tool to enter my progress). Here's where I'm at:

*** 91* ***
3** *2* *1*
175 **8 629

*52 *** 496
6** 5*9 237
*** *6* 185

5*6 8** 94*
*8* *5* **2
*** *94 ***

The hint is that Row 5, Column 3 should be a 1. I know that a 1 needs to go in either Column 2 or 3 of Row 5, but I am missing the logic that compels Column 3. I'm sure there's an obvious answer staring me in the face and that I'll feel like a fool when I find out, but I'm at a total loss right now. Any explanation would be greatly appreciated. Thank you.
Posts: 2
Joined: 21 June 2005

Postby simes » Wed Jun 22, 2005 6:42 am

1. row 8 has a subset of 4 and 9 in columns 1 and 3, so other candidates for these cells can be eliminated.

2. theres a "disjoint subset" with 4, 8 and 9 in cells (1,3)(2,3)(8,3). This allows you to update the candidates for (5,3) and (6,3)

Then you can place the 1 in (5,3)

(My attempt at explaining these techniques can be found from the link below by following the "techniques" link in the header.)
Last edited by simes on Sun Dec 11, 2011 9:56 am, edited 1 time in total.
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Location: UK

Postby jakeinprogress » Wed Jun 22, 2005 6:19 pm

Thank you. Predictably, it now seems obvious. But I read - and more importantly, processed - much of the link you sent me. Hopefully, my eyes will spot things more and more quickly with further repetition. No reason to think otherwise, I guess. Thanks again.
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Joined: 21 June 2005

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