## y-wing

Everything about Sudoku that doesn't fit in one of the other sections

### y-wing

G'Day Folks,

I'm starting to code y-wing strategy into my sudoku program.

The 'classic' representation of y-wing (from http://www.sudokuwiki.org/Y_Wing_Strategy) is:

Code: Select all
`  . .  . | . .  .  . AB . | . BC .  . .  . | . .  .  -------+--------  . .  . | . .  .  . AC . | . C  .where:  AB = pivot  BC & AC = pincers  C can be discarded.`

My question is, is it (also) possible to have:
Code: Select all
`  . .  . | . .  . | . .  .  . AB . | . BC . | . BD .  . .  . | . .  . | . .  .  -------+--------+--------  . .  . | . .  . | . .  .  . AC . | . C  . | . .  .  . .  . | . .  . | . .  .  -------+--------+--------  . .  . | . .  . | . .  .  . AD . | . .  . | . D  .where:  AB = pivot  BC & AC = pincers  C can be discarded.and  BD & AD = pincers  D can be discarded.`

In other words, can y-wing's pivots be "used" multiple times, using the same (where C = D) or different (where C != D) discard candidates?
speter

Posts: 16
Joined: 30 March 2017

### Re: y-wing

Welcome to the Sudoku Players Forum!

Yes, of course. Nothing about a Y-Wing "uses up" the pivot, so you are free to use the pivot in another Y-Wing. More generally, as long as the criteria for a Y-Wing are met, you can use it. It doesn't matter what other patterns are present at the time or what the history of your deductions up to that point is (as long as you haven't made any mistakes).

JasonLion
2017 Supporter

Posts: 641
Joined: 25 October 2007
Location: Silver Spring, MD, USA

### Re: y-wing

Thanks for the welcome and the answer.
speter

Posts: 16
Joined: 30 March 2017