The New Sudoku Players' Forum

[pistolero]

I've only been Sudoku-ing for a few days and have worked throuh the easy and medium puzzles at websudoku.com. This is my first attempt at a hard one and I'm not sure what the next step is. I haven't learned any of the formal techniques or formations yet (which is probably why I'm stuck), so what should I be looking for here?

Code: Select all

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

8 . 1   . 7 5   . 4 3
3 . 2   . 4 .   7 . .
7 4 5   3 6 .   8 . .

6 1 8   . 9 7   4 3 .
4 . 7   6 3 .   1 . .
9 . 3   . 1 4   . 6 7

[Hud]

One quickie is that 8 cn't go in row 9 box 9. since an 8 must go in row 9 somewhere, the only place left is in box 8.

[CathyW]

Code: Select all

 *-----------*
 |139|786|..4|
 |586|429|371|
 |274|153|...|
 |---+---+---|
 |8.1|.75|.43|
 |3.2|.4.|7..|
 |745|36.|8..|
 |---+---+---|
 |618|.97|43.|
 |4.7|63.|1..|
 |9.3|.14|.67|
 *-----------*

 
 *-----------------------------------------------------------*
 | 1     3     9     | 7     8     6     | 25    25    4     |
 | 5     8     6     | 4     2     9     | 3     7     1     |
 | 2     7     4     | 1     5     3     | 69    89    689   |
 |-------------------+-------------------+-------------------|
 | 8     69    1     | 29    7     5     | 269   4     3     |
 | 3     69    2     | 89    4     18    | 7     159   569   |
 | 7     4     5     | 3     6     12    | 8     129   29    |
 |-------------------+-------------------+-------------------|
 | 6     1     8     | 25    9     7     | 4     3     25    |
 | 4     25    7     | 6     3     28    | 1     2589  2589  |
 | 9     25    3     | 258   1     4     | 25    6     7     |
 *-----------------------------------------------------------*


These are the available candidates from your puzzle. Do you use candidates? If so, note the naked pair in box 9 (bottom right). This means you can eliminate 2 and 5 from r8c89 leaving another pair of 8 and 9. What can you then do in row 8?

If you're not familiar yet with some of the terminology for the techniques do visit:
http://www.simes.clara.co.uk/programs/sudokutechniques.htm
http://www.angusj.com/sudoku

HTH

[pistolero]

One quickie is that 8 cn't go in row 9 box 9. since an 8 must go in row 9 somewhere, the only place left is in box 8.

Wow, duh. Thanks. I must have been staring at it too hard and for too long

[pistolero]

I don't use candidates as I really haven't seen a need for them (yet). I find the idea of pencilmarking the puzzle to death (a la candidates) to be unappealing. I suppose it may be inevitable in the much harder puzzles though. I think putting the 8 in r9c4 unsticks me as the first reply suggests so I'll go from there.

Thanks for the web resources. I will definitely check them out. The more I learn about these puzzles the more interested I am in them!

[Hud]

Pistolero, it seems you're starting out the same way that I, and probably many others, did. Eventually we all hit a puzzle that is beyond our usual reasoning and pencilmarks will help solve it. Within reason, I try to get all the obvious answers and minimize the pencilmarks. Here in Phoenix, the puzzles in the newspaper increase in difficulty each day Mon thru Sat. I try to see how far I can get sans pencilmarks but the Sat ones usually require advanced techniques (like colouring and swordfish or at least x-y wings) to solve.
I'd heartily recommend that you get a free one month trial of Pappocom puzzles (if you haven't already) and work them on the computer. I find the Very Hards pretty interesting and if I get stuck, I print out the puzzle with all candidates and pencilmarks for solving while watching TV. I seem more able to see certain things like locked candidates better when I do them that way.

[CathyW]

Much depends on whether you are a candidate enterer or a candidate eliminator, at least initially. I do different puzzles both ways!

Most paper puzzles (i.e. printed and requiring me to write in numbers in pen or pencil), I prefer to do without candidates at all if possible. The extra hard ones generated on computer may be easier with candidates and some techniques such as colouring would be nigh on impossible without them or an extremely good visual memory.

[ravel]

Much depends on whether ...

Much depends on the weather, when its misty, i put them in

[ronk]

I print out the puzzle with all candidates and pencilmarks for solving ...

I don't believe I've ever printed out the candidates. (Aren't candidates and pencilmarks the same thing?) I print out the puzzle primarily so I've got space to pencilmark. When, and only when, there are four (or fewer) candidates, I'll write them in the four corners of a cell.

Hmm, that makes me wonder how I do line-box interactions. I'll have to peer over my own shoulder to figure that out.

[Hud]

Ronk, I'm having trouble remembering what to call numbers that have been placed. Maybe placements?

[Cec]

Hi Hud,
"big numbers" is what you're looking for - see here
Cec

[ronk]

"big numbers" is what you're looking for - see here

"Big numbers" is not commonly used. I see "placements" fifty times as often ... at a minimum.

[Cec]

"Big numbers" is not commonly used. I see "placements" fifty times as often ... at a minimum.

I don't like referring to "Big numbers" either but that's the recommended terminology. This is what I assumed Hud was asking. If "placements" is the preferred choice of members, which it seems to be, then perhaps the Terminology reference in the "Sticky" Thread should be changed.
Cec

[ronk]

If "placements" is the preferred choice of members, which it seems to be, then perhaps the Terminology reference in the "Sticky" Thread should be changed.

Only Pappocom can change that post.

[Cec]

"Only Pappocom can change that post."

Well, until they do, the recommended terminology is still "big numbers".
It's now 1.15am over here - I'll wind up now by supporting any procedure if other forum members agree of course, to have "placements" referred to in Terminology thread rather than "big numbers".
Cec