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| Is this an XY-wing? http://www.rcbroughton.co.uk/sudoku/forum/viewtopic.php?f=10&t=549 |
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| Author: | enxio27 [ Sat Jun 20, 2009 2:23 pm ] |
| Post subject: | Is this an XY-wing? |
Code: . . . | . . . | . . . . . . | . . . | . . . . 57 . | 47 . . | . . . ----------------------------------------- . . . | . . . | . . . . . . | . . . | . . . . . . | . . . | . . . ----------------------------------------- . . . | 45 . . | . . . . . . | . . . | . . . . . . | . . . | . . . Am I correct that this pattern would eliminate all other 7s in r3 and all other 4s in c4? |
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| Author: | Afmob [ Sat Jun 20, 2009 2:56 pm ] |
| Post subject: | |
This is an XY-Wing but it does not eliminate the candidates you mentioned. In this case the only elimination you could make is R7C2 <> 5. Here is how: If R3C4 = 4, then R7C4 = 5 If R3C4 = 7, then R3C2 = 5. So no matter what the placement of R3C4 is, one of R3C2 and R7C4 must be 5. So all cells which see both of them, cannot be 5. Therefore R7C2 <> 5 since it sees R3C2 and R7C4. |
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| Author: | enxio27 [ Sat Jun 20, 2009 6:20 pm ] |
| Post subject: | Re: Is this an XY-wing? |
Ok, I see that. Thanks! I think that's where I made my mistake on this puzzle on the last attempt. It makes the logic a lot more clear to see the three cells without all of the candidates in the other cells. |
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