Difference between revisions of "Unique Rectangle"

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(Created page with "A '''Unique Rectangle''' is a Deadly Pattern formed by 4 cells that share 2 rows, 2 columns and 2 boxes. In Sudoku Variations with additional constra...")
 
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Rows 1 and 2, columns 1 and 4 and boxes 1 and 2 each contain 2 cells from this pattern. All cells have candidates 1 and 2. There are 2 ways to complete this pattern.
 
Rows 1 and 2, columns 1 and 4 and boxes 1 and 2 each contain 2 cells from this pattern. All cells have candidates 1 and 2. There are 2 ways to complete this pattern.
  

Revision as of 20:35, 31 May 2020

A Unique Rectangle is a Deadly Pattern formed by 4 cells that share 2 rows, 2 columns and 2 boxes. In Sudoku Variations with additional constraints, each of these constraints must either contain 2 cells or none at all. All 4 cells only have candidates for the same 2 digits.

The name is not well chosen. The pattern causes the puzzle to have at least 2 solutions, so a better name would be non-unique rectangle.

Here is an example:

12 . .
12 . .
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12 . .
12 . .
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Rows 1 and 2, columns 1 and 4 and boxes 1 and 2 each contain 2 cells from this pattern. All cells have candidates 1 and 2. There are 2 ways to complete this pattern.

A more concrete example:

UniqueRectangleDeadlyPattern.png

This puzzle has two solutions.

A mistake to be avoided

The following pattern is sometimes mistaken for a unique rectangle. However, this pattern occupies 4 boxes.

This is not a unique rectangle!

. 1 .
. . 2
. . .
. 2 .
. 1 .
. . .
. . .
. . .
. . .
. 2 1
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. . .

See also

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