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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.