Forcing Chain

Forcing Chain Strategy is considered a last-resort method and is not endorsed by Logic Wiz. Many, including us, view it as more of a guessing technique rather than a logical process. Our apps do not feature puzzles that require this strategy. You might encounter it in our hints under the following circumstances:

• In the ‘Solve Your Own’ feature, when no other Sudoku strategy can solve the puzzle.
• In special puzzles created by Logic Wiz to demonstrate new solving techniques that are not yet implemented in the app.

The Forcing Chain strategy involves creating a sequence of if-then scenarios, starting with an initial assumption about a candidate in a specific cell. By following the chain of implications, you can determine whether the assumption leads to a contradiction or confirms a candidate’s placement. If all possible outcomes from an assumption converge on the same conclusion or eliminate a candidate, you can confidently place or remove that candidate from the grid. This method helps resolve ambiguities by leveraging logical outcomes. When using a Forcing Chain, it is advisable to start with a cell containing bi-value candidates.

Example

By following the chain of events resulting from placing 1 in B2, you’ll eventually reach a contradiction in the puzzle. Therefore, 1 can be eliminated from B2, confirming that B2 = 4. We do not elaborate on the chain of events, as it is a tedious process, which we consider more akin to ‘guessing’ rather than applying a logical method.