The Unique Rectangle technique is an advanced Sudoku solving strategy that helps you eliminate candidates in certain complex scenarios. It involves identifying a rectangle formed by four cells in two rows and two columns with specific candidate combinations.
How to Identify a Unique Rectangle
A Unique Rectangle pattern consists of the following characteristics:
Four cells forming a rectangle in two rows and two columns.
All four cells must contain the same two candidate numbers (X and Y).
At least two of the cells must be empty (not contain a solved number).
How the Unique Rectangle Technique Works
If the above conditions are met, and if the four cells were to contain only the numbers X and Y, then the puzzle would have multiple solutions. To avoid this, you can eliminate candidates from cells that see two or more corners of the rectangle.
Example of the Unique Rectangle Technique
Tips for Spotting Unique Rectangles
Look for rectangles formed by four cells in two rows and two columns.
Focus on cells that contain the same two candidate numbers.
Remember that at least two of the cells must be empty.
