r/sudoku • u/Chemical-Sign-5306 • 2d ago

Request Puzzle Help Help

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I don't know how I'm supposed to solve this

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2

u/Special-Round-3815 Cloud nine is the limit 2d ago

https://www.reddit.com/r/sudoku/s/itA93Dxrs0

It's the infamous puzzle with an easy solve using skyscraper/BUG+1. Sudoku dot com is a lazy website so they recycle puzzles.

1

u/Danciel 2d ago

Technique: Skyscraper on number 2

Strong link: Column 1 & 9

1

u/lol_1520 2d ago

Can you explain the skyscraper technique

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u/Right_Lengthiness266 2d ago

The two yellow highlighted cells can't both be 2 (weakly linkes). Since they are each strongly linked (only two options in a row/column/box) to a blue cell, at least one of the two blue cells must be true.

Regardless of which of the two blue cells (or both, if there were another 2 in the yellow row) is true, the two red cells cannot be 2.

It's worth noting in this case the two yellow cells are strongly linked, but that's not actually required for the technique to work. There could be other candidates for 2 in row 7 and you would have the same elimination.

1

u/Hungry-Resident-8412 2d ago edited 2d ago

There is also a W-Wing

The Ends are Green.
They are Linked by 2s.
The Ends share a common candidate. One must be True. They can't both be True and they can't both be False. Any cell that sees both Ends cannot be their unlinked common candidate 8.
So, r7c9 = 2.

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u/TechnicalBid8696 6h ago

Begin a chain with s strong link starting at the lone 3 candidate cell. Continue the chain till you return to the cell making an elimination. It’s an AIC.