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| Solving Help http://www.rcbroughton.co.uk/sudoku/forum/viewtopic.php?f=5&t=1748 |
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| Author: | turneraw [ Thu Mar 14, 2024 3:44 pm ] | ||
| Post subject: | Solving Help | ||
I am a very good player, but not the experts that others here are. I need help on a puzzle that seems like it should be easy to solve, but I am completely stumped. I don't want anyone to tell me the answer; I just want someone to tell me what solving technique I need to employ to solve the attached puzzle.
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| Author: | rcbroughton [ Thu Mar 14, 2024 5:15 pm ] |
| Post subject: | Re: Solving Help |
turneraw wrote: I am a very good player, but not the experts that others here are. I need help on a puzzle that seems like it should be easy to solve, but I am completely stumped. I don't want anyone to tell me the answer; I just want someone to tell me what solving technique I need to employ to solve the attached puzzle. There are a couple of techniques that would work from here. I would suggest looking at XY-Wing using a strong link. In the puzzle you have, there is a chain of strongly linked cells (A B C D) ("strong" here means that there is a value X or Y which must be in one or the other) such that (AB) are linked (BC) are linked (CD) are linked and (DA) are linked You can sometimes think of it as a mini trial and error - a what-if - that leads to a contradiction by following a short series of linked cells. So you examine the forcing sequence if A = X then B = (not) X if B = (not) X then B = Y if B = Y then C = (not) Y if C = (not) Y then D = Y but you have a situation where (AD) must be a third value Z - but you have just come to a contradiction because (AD) = XY The power comes from identifying a series of "conjugate pairs" - sets of cells where (AB) are in the same row or column or box and a value must be in one of them; and "pivoting" cells where there are only 2 possible values - and then using those as your XY to look for the chain. |
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