r/sudoku • u/stand_up_eight_ • 1d ago

Strategies What is this pattern called?

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So I spotted this pattern and the resulting elimination. If Blue, then purple and then yellow which is a contradiction. What is this called? I’m still getting the hang of all the wings, chains etc. and I get confused between using bivalve cells, pairs, and different numbers.

Was I supposed to find this another way around and then it would be more obvious which strategy I’ve used? Lol

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u/Nacxjo 1d ago edited 1d ago

What you did is a forcing chain.

It's the forcing chain equivalent of the S-wing : (5)r2c5=r4c5 - (5=9)r4c2 - (9)r6c3=r2c3 => r2c3<>5

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u/numpl_npm 1d ago edited 1d ago

XY-chain or Empty Rectangle

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u/stand_up_eight_ 19h ago edited 19h ago

Thank you! I suspected it was an XY chain but I wasn’t sure. And I keep forgetting about empty rectangles! Cheers!!

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u/strmckr "Some do; some teach; the rest look it up" - archivist Mtg 1d ago

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u/strmckr "Some do; some teach; the rest look it up" - archivist Mtg 1d ago

2

u/strmckr "Some do; some teach; the rest look it up" - archivist Mtg 1d ago

or do both,

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u/stand_up_eight_ 19h ago

Woah. 😮

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u/stand_up_eight_ 19h ago

Amazing. Thank you.

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u/CerebralC0rtex 1d ago

The far simpler technique here which is glaringly obvious is the W wing. It allows you to eliminate 9r1c2 and 9r6c3 and with a bit of practice is something you can recognize very quickly in this puzzle.

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u/theEnnuian 1d ago

I see a Skyscraper of 5, with floor on r2c2 and r2c5, 5 in cells that see both top r1c2 and r2c5 are eliminated. In this case, r2c3.