Minimum (given numbers) before guessing?

stevegnet

Hi all, hope this quetion is in the right forum? (if not can a MOD move)

What is the minimum number of (given numbers) a Sudoko puzzle needs to have to be completed without having to guess a number in a position to be able to continue?

I know 17 is the minimum numbers required for a unique completion.

The reason I ask is I started a puzzle which had 27 numbers given at start. I progressed to finding another 13 numbers IE:- 41 in total so far.

Have penciled in all combinations of remaining numbers.

I have used a couple of internet solvers to prove the numbers can work to complete. A couple of solvers when I entered the initial 27 numbers stopped when they got to where I am with the further 13 numbers?.

Hope this makes sense and thanks in advace for any replies....Steve

Initial numbers are:-

-3---52--
4--31--6-
8-----7--
7-2-3----
56----9-8
----2-3--
-5-4----9
-46--75--
---1--4--

with numbers I have found:_

63-8752--
4--31-865
8-5--47--
7-2-3----
563741928
--4-2-3--
-5-4----9
-46--75--
---15-4--

JasonLion · Posted: Sun Jan 24, 2010 2:01 pm Post subject:

That puzzle has a unique solution. After filling in 14 digits fairly easily it suddenly requires some fairly complex solving techniques. I would use a finned X-Wing and a W-Wing, though there are other ways to do it. After that it gets simple again.

lkSudoku

daj95376

stevegnet · Posted: Sun Jan 24, 2010 7:22 pm Post subject:

OK thanks for the replies,

I am new to this and have completed a number of sudoku puzzles recently. I didn't realise just how involved and complicated a "SIMPLE??" puzzle could be I guess.

. I have been pulling my hair out for the past week trying to see a logical answer to this puzzle. I keep leaving it and coming back trying with a fresh mind.
Having since looked up a few of these weird names of strategies suggested and even more confused would it be possible for someone on here to work out the next number in the above puzzle so I can try to see why without guessing??

Thanks again Steve.........very confused.

hobiwan · Posted: Tue Jan 26, 2010 5:58 pm Post subject:

Assuming you arrived at this state:

stevegnet · Posted: Sat Mar 20, 2010 2:42 pm Post subject:

Well after coming back to this puzzle after about 2 months now each week it seems I have finally completed it. I did however try to understand these various named strategies posted to no avail. I would like to thank those who replied....THANK YOU!!!

Here's my logical? approach to it:-

The 2's in box 1 eliminate the 2 at r8c2
The 1,2, 3's in box 7 column 1 eliminate the 9's in box 7 column 1
Therefore the remaining 9 in column 1 is in r6c1

The rest is straight forward from there on........Well it worked for me Very Happy

stevegnet · Posted: Sat Mar 20, 2010 3:30 pm Post subject:

Ooops!

over looked the possibility of the 1 in r7c3 which puts the spanner in the works to my theory even if result was correct?. Confused

Back to the drawing board. Rolling Eyes