XYZ-Wing: Advanced Solving Sudoku Technique
XYZ-Wing by createclassicsudoku.com , and sudokuwiki.org/XYZ_Wing , and http://www.sudokusnake.com/xyzwings.php
XYZ-Wing:
Courtesy from http://www.sudokusnake.com/xyzwings.php
An XYZ-Wing is like an XY-Wing in that it is a group of three cells, one sharing a unit with the other two. However, the first cell in an XYZ-Wing has three candidates while the other two, called the wings, have two. Each of the wings must share one candidate with the first cell, (that's part of sharing a unit) but of different values. If the second candidates in the wings are both the same, and are also the same as the extra candidate in the first cell, then if any fourth cell shares that candidate and a unit with all three, that candidate can be eliminated.
Below is an example of using XY-Wing-RowBox(one case of XY-Wing in our Sudoku solver, explained after the example) to refine the candidate values of R3C6 (the highlighted square that is not circled in red). Blank/Empty Squares are marked with candidate values in red.
