The X-Cycle technique is an advanced Sudoku solving strategy that helps you eliminate candidates in certain complex scenarios. It involves identifying a cycle of strong and weak links between candidates in a row, column, or block.
How to Identify an X-Cycle
An X-Cycle pattern consists of the following characteristics:
A chain of cells in a row, column, or block, where each cell contains a specific candidate number.
The chain must alternate between strong links and weak links.
A strong link exists when a candidate number appears in only two cells within a row, column, or block. If one of these cells contains the number, the other cannot.
A weak link exists when a candidate number appears in more than two cells within a row, column, or block.
The chain must form a closed loop, meaning the last cell in the chain must see the first cell.
How the X-Cycle Technique Works
If the above conditions are met, and if all links are strong, then the puzzle has multiple solutions. Therefore at least one link must be weak. If a cell outside the cycle sees both ends of a weak link, then that cell cannot contain the candidate.
Example of the X-Cycle Technique
Tips for Spotting X-Cycles
Look for candidate numbers that form chains in rows, columns, or blocks.
Focus on alternating between strong and weak links.
