## What do you get if you cross an ER with a Y-wing?

Advanced methods and approaches for solving Sudoku puzzles

### What do you get if you cross an ER with a Y-wing?

(no, that's not a joke.)

I ended up with this. I don't know what it is.
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`/./|./.|......|.1.|..././|./.|...---+---+---...|./.|....@.|./.|......|./.|...---+---+---...|.1.|......|./@|......|./.|...1=cell with candidate 1/=cell without candidate 1@=bivalue cell 12r7c2<>1r8c2<>2r5c6<>2`

It's not thwo techniques off the same strong link because r5c2 doesn't see the strong link.
What technnique is this? It looks like some sort of kraken fish but I cannot tell.
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Once upon a time I was a teenager who was active on here 2007-2011
999_Springs

Posts: 367
Joined: 27 January 2007
Location: In the toilet, flushing down springs, one by one.

I think it really is two nice loops in one. The inner one is just the ER:
-1- r123c2=1=r2c123 -1- r2c5=1=r7c5 -1- => r7c2<>1

Attach the two bivalues and you get the other two eliminations:
-2-r5c2-1- r123c2=1=r2c123 -1- r2c5=1=r7c5 -1-r8c6-2- => r5c6|r8c2<>2

Note that this isn't a Y-wing, but is similar. A Y-wing is a nice loop with three elements. This is a four element strong grouped nice loop, but eliminations work the same way. For more information on nice loops and variations you can check out the Collection of Solving Techniques.
Mike Barker

Posts: 458
Joined: 22 January 2006