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Unique Rectangle Type 5

When diagonal or three roof cells share one extra candidate.

Explanation

Type 5 keeps the deadly rectangle idea but lets the shared extra candidate sit in diagonal roof cells or in three corners of the rectangle. One of those roof cells must contain the extra candidate, so any cell that sees all of them can remove that candidate.

Unique Rectangle Type 5 example Sudoku board 6 5 8 9 1 3 1 5 9 3 8 6 8 9 3 1 6 7 5 2 8 6 9 3 2 5 4 1 3 5 9 6 1 2 7 8 1 2 4 8 7 5 6 3 9 6 7 2 3 8 4 1 9 5 9 3 8 5 1 7 4 2 6 5 4 1 6 2 9 3 8 7
An example board where Unique Rectangle Type 5 applies

Practice tip

Confirm the floor cells still hold only the base pair. Then check which outside cells can see every roof cell with the shared extra candidate.

Example steps

  1. Find a unique rectangle with a repeated base pair.
  2. Mark the two diagonal or three roof cells that contain the same extra candidate.
  3. Remove that extra candidate from cells that see all marked roof cells.

Try this technique on a real puzzle.

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