Unique Rectangle Type 5

Unique Rectangle Type 5 occurs when two diagonal cells of the rectangle share an extra candidate beyond the deadly pair. To avoid the deadly pattern, one of these diagonal cells must contain the extra candidate.

Technique

1. Find a potential deadly rectangle with candidates {X,Y}.
2. Two diagonally opposite cells have the same extra candidate Z.
3. To prevent the deadly pattern, at least one diagonal cell must be Z.
4. Eliminate Z from cells that see both diagonal cells containing Z.

Tips

• Type 5 works with diagonal corners rather than same-side corners like Type 2.
• The extra candidate Z appears in exactly two diagonally opposite cells.
• A variant exists where Z appears in three of the four cells.