Skyscraper is a pattern that uses two rows with a candidate in exactly two positions each.
Understanding the Concept
Two rows each contain a candidate exactly twice.
One column connects the two rows (the "skyscraper").
The other positions are in different columns.
Creates a strong inference chain.
Eliminates the candidate from cells seeing both "base" positions.
Can also work with two columns affecting rows.
Simpler than X-Wing but based on similar principles.
Examples
Skyscraper Example
Candidate 4 in R2C3,R2C7 and R8C3,R8C9. Eliminate 4 from cells seeing both R2C7 and R8C9.
Pro Tips
- •Look for candidates appearing exactly twice in two rows
- •One column should connect them (the skyscraper)
- •Eliminations at the base of the pattern
- •Often easier to spot than X-Wing
