20170628, 14:43  #1 
"Matthew Anderson"
Dec 2010
Oregon, USA
2^{3}·149 Posts 
a partial sudoku puzzle
Hi MersenneForum,
I picked up a Sudoku book today and tried again at a puzzle that had stumped me before. I was able to put in the number 8 near the center and then I was again stumped. I know there are some advanced Sudoku techniques out there, on the internet. Can anyone tell me a next step ( with logic) for the attached puzzle? Also the possibility of a machine solver has been considered. This is from the "New York Post Bloom Sudoku Book" (fiendish puzzles c 2013). I am stuck on page 31. I do not want to 'reverse engineer' the puzzle by looking in the answer section. Regards, Matt 
20170628, 15:14  #2 
Aug 2006
1011101100100_{2} Posts 
Well, in the topright box you can fill in a 6 (in the bottommiddle position) because nothing else in the middle column can be a 6. Similarly the middle row across the top has only one position to put a 9, the middle of the left grid. That forces the "49" at the bottom to 4 and the "47" above it to 7, and probably cascades further.

20170628, 21:14  #3  
"Forget I exist"
Jul 2009
Dartmouth NS
2^{2}·7^{2}·43 Posts 
Quote:
Lets rewrite it here, on the forum ( in roughly,original form), instead of the file and rotating it: now it's mostly a combination of set union, and set difference to consider. Last fiddled with by science_man_88 on 20170628 at 21:27 

20170628, 21:36  #4  
If I May
"Chris Halsall"
Sep 2002
Barbados
10101110110101_{2} Posts 
Quote:
"2" is the only possible solution for 2x,5y. Everything simply cascades. Last fiddled with by chalsall on 20170628 at 21:43 

20170629, 07:14  #5 
"Matthew Anderson"
Dec 2010
Oregon, USA
2^{3}×149 Posts 
thanks
Hi Mersenne Forum,
Thank you to all the responses to this thread. I see Greathouse's reasoning for a 6 in the bottom row of the top right 3 by 3 grid. Now this one should be easy. Regards, Matt 
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