Need a sudoku hint...

[Alex Franke]

This is the first sudoku that has me really stuck... Am I missing something simple here? Did I make a mistake?

Can anyone give me a hint by telling me the next number and why?

This is how far I got:

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

This is how it started:

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

[Copper]

9 in the top row center. Now I'm trying to figure out why I said that...

In the center column, you can have only an 8 or a 9 in the top and bottom. The nine can't be in the bottom because of the way the 8's would work if you fill them around.

[Russianwolf]

I finished it.

Sometimes on the harder ones, when you have only two possible numbers for a square, you have to plug one and go forward to see that it won't work.

"if I put an 8 there, that make this a 4, this a 3, and that a 7. No, there's already a 7 in that row so that 8 should be a 4."

That is still logic and isn't a guess, but reasoning.

I did it with the 8 and 5 in the bottom left of this one.

[crokett]

On bottom row, middle square, middle row is 2. This is because in middle row middle square, 2 can only go in either left or right column.

[tfischer]

Sometimes on the harder ones, when you have only two possible numbers for a square, you have to plug one and go forward to see that it won't work.

One of my Sudocu books said that with a 'proper' puzzle, you should never need to guess like that. Not sure if that's true or just someone's opinion...

If you google "Sudoku Solver" you can find sites that let you plug in a puzzle and give you hints...

-Tim

[gerti]

If you really want to knock yourself out on advanced strategies:

http://www.scanraid.com/Strategy_Families

[Alex Franke]

Thanks, guys. I'll try these hints out today.

[gsmittle]

You won't like my solution:

Put the puzzle down and back away slowly...

g.

[Salty]

I like working these puzzles.
At least I did until you put up this thread.
Also, I thought I was good at it...again, until you put up this thread.
If I may ask. What difficulty level is this one? Most of the difficulty ratings I see are in 'stars' and beyond that they call then maddening or insane.
I have sent too much time on this and cannot get it further than you did. I even started all over and reworked it and still end up here.

Silly humans..wasting time on such things!

[Alex Franke]

Yeah -- I know -- they're addicting.

This one was a 4 out of 4.

I feel like I'm just of the brink of discovering a strategy for this one to make it easier to try one of two options, then find out what impact it has down the line. I've been avoiding the strategy websites because I want to try to figure out the strategies by myself...

[Salty]

Well, I have worked a lot of 4-star puzzles but this one has me beat....at least for now.
I too have resolved to work them through logic and not guess.
I'll get it eventually and I'm sure you will too.
May take weeks....but I will solve it.
Thanks.....I think!!

[Salty]

Well Alex, I have the solution.
However, you may not want me to solve it for you but rather perhaps you want that hint.
My way of getting there was a bit unorthodox as I basically guessed and then reverse engineered the logic. I'm sure that explanation is a clear as mud.
To put it simply, I figured out a pattern where the logic proved to be an impossibility and therefore it proved that choice to be false. So far I cannot totally relate it to any of the patterns/strategies on the webpage link but it does have to do with linked pairs. I already knew about those but never knew it to have a proper term.
Anyway, if you want, I can identify the linked pairs that I used.

Salty

[Alex Franke]

Anyway, if you want, I can identify the linked pairs that I used.

I many take you up on that. I was hoping pick it up again this weekend, but never got around to it. I'll take another stab at it with fresh eyes this week and let you know if I need your hint. (I often do these on the bus on the way to and from work...)

[Salty]

Sounds like a good way to miss your stop!

hehe

[chopnhack]

If your still puzzling away on this one Alex, try

625 394 871 for your top row
478
931

846
592
317

789 465
153
264 183 795

hope this helps