The New Sudoku Players' Forum

[dneely]

I'd like an easy way to start to identify them

[angusj]

I'd like an easy way to start to identify them

Put your reading glasses on then

</ feeble attempt at humour>

[CathyW]

Using Simple Sudoku, I use the facility to highlight the bivalue cells as the first step in identifying any xy-chain that may be in a puzzle.

[thomas]

Hi, have been trying to solve more difficult puzzles- sunday times sudoku not doing too badly but thought its about time i knew what an x-wing is!

[TKiel]

Thomas,

Visit www.angusj.com for an explanation. There is also an explanation in the 'help with particular puzzles' forum under the "stuck, any ideas' thread. I wrote that post but I think the one at the website above is better or at least more concise.

Tracy

[evert]

I like the explanation given here:
http://www.simes.clara.co.uk/programs/sudokutechnique11.htm

I wonder if XY-wing could be explained in the following way:
If value Z MUST be filled in exactly one of two given cells then every 3d cell that looks at both of these two cells cannot contain Z.

The first two cells do not necessarily share a house.

[TKiel]

Evert,

The link contains a good description of an xy-wing but I thought thomas asked for an explanation for an x-wing. (A little off topic maybe.) That might have only been a typo on his part, in which case my suggestions are irrelevant and yours are appropriate.

Tracy

[Animator]

Actually, the 'off-topic' post is the one of thomas. (off-topic by one letter that is )

dneely started the topic and used the title 'xy chains'.

Then thomas replied and asked for an explanation of x-wing(s).

[emm]

I see the hackers took my post about bottom feeders, twitchiness and off-topic polarisation ... so be it ... I'm not going over all that again.

However since I don't know if dneely is still wondering, here's the old link to finding XY chains
http://forum.enjoysudoku.com/viewtopic.php?p=12753#p12753