Sudoku Players' Forum (clone)

XY wing is a powerful technique of elimination, which has the disadvantage that the third cells of the chain can be laborious identified. Specially the beginners meet with difficulties in finding XY wing model, and insistently solicit help on web sites:
http://www.intosudoku.com/forum/viewtopic.php?t=99&sid=da2df1dee2df9a7518ec5da5950a99c1

In the study
„Algorithm for identification of the XY wing from the Sudoku grid”
attached to the site:
http://www.sudoku.org.uk/discus/messages/2/3787.html?1174859479

I propose a simple method for identification of the XY wing, which I submit to your analysis.
I'm using now almost exclusively the graphic variant with nonagon, in order to identify XY models from grids.

Mihail Iusut, Romania

I disagree. XY wing is rarely needed.

Powerfull suggest lots of eliminations, extreme simplification.

Here is another tutorial on finding xy-wings
http://forum.enjoysudoku.com/viewtopic.php?p=36266&highlight=#36266