Technique to solve this puzzle

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Technique to solve this puzzle

Postby batata004 » Wed Dec 26, 2018 3:55 pm

Hi,

I am wondering if there is some objetive technique to solve this sudoku attached. I already tried X-WING, XY-WING, SWORDFISH and others like that but it looks like nothing works out.

I know at this stage of the puzzle I could "guess" some numbers and try finding the remaining options, checking if it matches or getting to an "impossible solution" (in this case I would discard such guess).
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sudoku.jpg
sudoku.jpg (83.21 KiB) Viewed 161 times
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Re: Technique to solve this puzzle

Postby qiuyanzhe » Thu Dec 27, 2018 11:07 am

Chain on 8:
(Turbot Fish)
r3c6(8)==r1c4(8)--r1c2(8)==r7c2(8)
eliminates r7c6(8)
*edit: corrected spelling error ;)
Last edited by qiuyanzhe on Thu Dec 27, 2018 11:23 am, edited 1 time in total.
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Re: Technique to solve this puzzle

Postby StrmCkr » Thu Dec 27, 2018 11:21 am

skyscraper
row 3 and row r7 digit 8 => R1C2,R9C1 <> 8
Some do, some teach, the rest look it up.
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Re: Technique to solve this puzzle

Postby eleven » Thu Dec 27, 2018 7:56 pm

Or uniquness pattern 24 in r23c1,r12c3,r13c8 -> one of 8r3c1 and 8r1c4 must be true => r1c2=2.
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Re: Technique to solve this puzzle

Postby RSW » Thu Dec 27, 2018 8:40 pm

Nothing more than a naked pair: r2c4 & r4c4 have identical candidates: 2 & 4.
Remove candidate 2 from r1c4 & r8c4.
Remove candidate 4 from r1c4.
Cell r1c4 now has only one possible value: 8
From there on, everything is singles.
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Re: Technique to solve this puzzle

Postby SpAce » Thu Dec 27, 2018 10:07 pm

RSW wrote:Nothing more than a naked pair: r2c4 & r4c4 have identical candidates: 2 & 4.
...
From there on, everything is singles.

A (partially) good observation, and a small wonder no one else mentioned that. With the presented board that's clearly the simplest solution. However, would you agree that some solved cells in the board don't make much sense even though they're all technically correct? Specifically, how were 5r2c5 and 9r2c8 solved? I don't see any obvious way to do that at this stage (except nets, but such complexity makes little sense here). I bet the other replies were based only on the givens, and the two mysteriously solved cells and the resulting naked pair went unnoticed (because they would not appear in a normal solve path).
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Re: Technique to solve this puzzle

Postby batata004 » Fri Dec 28, 2018 8:55 pm

Wow I learned a lot with your techniques and observations! I am starting to adventure into diabolic/expert sudoku and those techniques are really a must! Thank you so much!
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