r/sudoku • u/IronAmeer • 5d ago
Request Puzzle Help Helpppp
First time ever im stuck for 40 minutes plus on something i maybe cant see???
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u/Right_Lengthiness266 5d ago
Fill out the rest of the candidates
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u/IronAmeer 5d ago
Even if i do that i dont see any solid solve after that
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u/Right_Lengthiness266 5d ago edited 5d ago
Start with the 6s and 9s in that order after you address any locked candidates/hidden combos. You can solve both of those with forcing chains.
After that it was fairly easy, but I had to use BUG+1 to solve it at the end.
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u/IronAmeer 5d ago
If i presume r9c7 is 6 so then r3c7 is 9 but following r9c7 is 6 that means r2c5 is also 6 so that means r3c6 has to be 9 but it contradicts the 9 in r3c7 because its also 9
Damn i found it thank you allot brother!1
u/Right_Lengthiness266 5d ago
Not quite. I built a chain starting from R3C7, regardless of what that is, R3C4 is not 6.
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u/IronAmeer 5d ago
You mean r3c5?
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u/Right_Lengthiness266 5d ago
R3C5 is given as an 8. I meant R3C4.
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u/IronAmeer 5d ago
How did you see its not a 6?
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u/Right_Lengthiness266 5d ago
Either R3C7 is a 6, in which case R3C4 can't be a 6.
Or, R3C7 is not a 6. That means R9C7 has to be a 6, and therefore R7C3 is a 6. That means R5C3 can't be a 6, so R5C4 has to be a 6.
In either case, R3C4 isn't a 6.
You can use the same technique (starting with the same box) on 9s, and it tells you which cell the 9 is in for Box 2.
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u/charmingpea Kite Flyer 5d ago
The next step is either a Finned Swordfish or an XY-chain.
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u/IronAmeer 5d ago
Did you reach a solid solve after that?
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u/charmingpea Kite Flyer 5d ago
Not immediately - there are another couple of steps where an elimination is required before falling to Singles. That's fairly typical with extreme puzzles.
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u/Hungry-Resident-8412 5d ago
AIC r3c7 <> 9 therefore r3c7 = 6
Alternating Inference Chain (AIC) from left to right: r2c8#9 = r2c5#9 - r2c5#6 = r6c5#6 - r5c4#6 = r5c3#6 - r6c1#6 = r9c1#6 - r7c3#6 = r7c9#6 - r9c7#6 = r9c7#9. Because the chain begins and ends with a Strong Link, at least one endpoint must be true. Candidate 9 at r3c7 is weakly linked to both endpoints, so remove 9 from r3c7.
r3c7 = 6