Mirrored from **Sudopedia**, the Free Sudoku Reference Guide

# Double Crossover

In Sudoku-X, the **double crossover** technique can be stated as follows:

- Consider a digit
**X**. Suppose the leading diagonal contains only two cells that has **X** as a candidate, call them **A** and **B**. Suppose the non-leading diagonal contains only two cells that has **X** as a candidate, call them **C** and **D**. If **A** and **C** are peers, then we can eliminate **X** from any cell that is seen by both **B** and **D**.

The double crossover technique can be replicated using Color Wing with two clusters, or by using the following chain:

(X): B = A - C = D

Double crossover is a special case of Triangular Connection.

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This page was last modified 10:13, 9 January 2008.