Sudoku Help
 

Anyone here really good with sudoku puzzles? This is the first time I've been suck on one. I don't want it solved, but need advice on how to proceed.

The first image is how far I've gotten and the second list all the pairs I could find.

I'm assuming there some technique needed, that I'm not familiar with, to proceed.

Attachment 996889

Attachment 996890

:iono:

If the one pair in the top middle, can ONLY be a 4, and another pair later can be a 4 or a 3... I think you can easily fill in that row.

Then another couple can easily fill in based off of that, and it should snowball to a solution pretty quickly for you.

Thanks for pointing me towards the two pairs of fours.

I still don't see the "easy to fill that row" part, but will concentrate around the fours to see if I can spot it.

The second row should be easy to finish after you get that 4 in.

I look for exclusion sets. What I mean is, there are a number of boxes that MUST contain numbers from the same subset. Simplest is a pair, but 3s can be very handy as well.

This example isn't from your puzzle, but lets say you've got a row that looks like this (big numbers are givens/filled in for sure, slashes are the only options for those boxes, based on unseen clues)

|2 __ __ | 3/6 __ 6/8 | __ 7 3/6/8|

Those blank spaces cannot contain a 3,6, or 8 since you know they have to go into 3 other spots that row. So those blanks must therefore contain the numbers 1,4,5, and 9.





One other technique that I use when stuck, though more for Kakuro than Sudoko, is to take a space with 2 or 3 options, pick one, and follow the chain of possibilities (in my head or on some scrap paper or something) that the choice forces until one of 3 things happen:

1. results in a contradiction
   
2. it solves the puzzle, or
   
3. things stall out inconclusively one way or the other
   

If #3 happens, I just choose another option for the same box and go through it again. If thats inconclusive too (very rare), I'll go to another box not directly linked to the first one.

This shouldn't been needed for Sudoku (at least, not anymore ... there was a time where it was required on some of the most difficult puzzles), but its real handy when you've got a half solved puzzle and don't see a way forward.

Thanks guys!

I'm just going to have to come back to this one later. I hate to just drop a number in without knowing the mathematical proof going on in the background.

I guess I need to stay at a Holiday Inn Express!

:lol:

So the Battlefield 3 "spam" post pulled me into this section where I saw my thread from last year.

With a fresh new look, in about 5 minutes, I can now see what I was missing before. The 3,4,7 closes it's subsection leaving only one place for the 6... which in return easily opens up the puzzle!

Attachment 1034211

:bow:
:happy0180: