SudokuSolver Forum http://www.rcbroughton.co.uk/sudoku/forum/ |
|
Regular Samurai #16 http://www.rcbroughton.co.uk/sudoku/forum/viewtopic.php?f=16&t=230 |
Page 2 of 2 |
Author: | enxio27 [ Tue Oct 26, 2010 1:23 am ] |
Post subject: | Re: Regular Samurai #16 |
Børge wrote: Can you see the elimination(s) now? I had the right cells, but it took me a while to find one elimination (5 in R4C1). We'll see how far that gets me. UPDATE: OK, that did the trick! Thanks, Børge! I'm just not sure I could recognize a similar scenario if I saw one again. Was that a Y-wing or an XY-X chain you showed me? I can't seem to find either one (at least by those names) in Tom Davis' monograph. |
Author: | Børge [ Tue Oct 26, 2010 2:51 pm ] |
Post subject: | Re: Regular Samurai #16 |
The correct elimination is r6c4 <> 5 using the following Y-Wing: Here one possible general description of a Y-Wing:
In the above Y-Wing: W1 = r4c5 W2 = r4c8 W3 = r5c4 W4 = r6c8 |
Author: | enxio27 [ Tue Oct 26, 2010 3:14 pm ] |
Post subject: | Re: Regular Samurai #16 |
Børge wrote: The correct elimination is is r6c4 <> 5 using the following Y-Wing: Now I see it! I must have taken a harder path using all five of those highlighted cells to eliminate the 5 in r4c1. Quote: Here one possible general description of a Y-Wing: Thanks for that! I'll have to study it out some more so I can get a handle on it to recognize it again. Out of curiosity, do I really need the r4c58 to eliminate the 5 in r6c4? BTW, did you go back and delete part of your above post? I could have sworn there was some description of 2-string kite and another technique being special cases of the Y-wing, but now it's gone. |
Author: | Børge [ Tue Oct 26, 2010 3:44 pm ] |
Post subject: | Re: Regular Samurai #16 |
enxio27 wrote: Now I see it! I must have taken a harder path using all five of those highlighted cells to eliminate the 5 in r4c1. You can use a 4 cell chain (XY-X-Chain I think, getting a bit rusty so I have to think it over) r4c8 -> r6c8 -> r6c4 -> r4c5 to prove that r4c1 <> 5.Here a Y-Wing, which proves that r4c1 <> 5 Hidden Text: enxio27 wrote: Out of curiosity, do I really need the r4c58 to eliminate the 5 in r6c4? If you have any suggestions on how to eliminate the 5 in r6c4 without using r4c58, I am all ears!enxio27 wrote: BTW, did you go back and delete part of your above post? I could have sworn there was some description of 2-string kite and another technique being special cases of the Y-wing, but now it's gone. YES, I did go back and delete part of my above post. I wrote that Two-String Kite and Skyscraper are special cases of the general Y-Wing. This is of course absolute rubbish. As I said above, getting a bit rusty from not having solved sudokus in a while.
|
Author: | Børge [ Tue Oct 26, 2010 6:09 pm ] |
Post subject: | Re: Regular Samurai #16 |
enxio27 wrote: I had the right cells, but it took me a while to find one elimination (5 in R4C1). enxio27 wrote: I must have taken a harder path using all five of those highlighted cells to eliminate the 5 in r4c1. You probably used the following chain, AFAIK called an XYT-Chain: This is the more formal XY-X-Chain: |
Author: | enxio27 [ Tue Oct 26, 2010 8:35 pm ] |
Post subject: | Re: Regular Samurai #16 |
Børge wrote: If you have any suggestions on how to eliminate the 5 in r6c4 without using r4c58, I am all ears! Never mind! Just my faulty logic again. enxio27 wrote: YES, I did go back and delete part of my above post. Ok, just making sure I'm not going crazy! LOL! Quote: You probably used the following chain, AFAIK called an XYT-Chain: Yes, that's it! The more advanced the techniques get, the longer it's taking me to work out the logic behind them. I'm still wrapping my brain around the Y-wing. |
Author: | Børge [ Tue Oct 26, 2010 8:57 pm ] |
Post subject: | Re: Regular Samurai #16 |
enxio27 wrote: I'm still wrapping my brain around the Y-wing. Brain exercise is almost always a good thing.The logic behind the Y-Wing is fairly simple. Spotting one is a total different story. Again my definition of a Y-Wing:
1. says that in a given house the digit X can only be placed in one of the two cells W1 or W2.
|
Page 2 of 2 | All times are UTC |
Powered by phpBB® Forum Software © phpBB Group https://www.phpbb.com/ |