Region Confinement
Learn how to use regions confined to a single row or column for powerful deductions.
IntermediateWhat Is Region Confinement?
Region confinement occurs when all remaining valid cells in a region fall within a single row or column. When this happens, you know the queen for that region must be in that row or column — which means no other queen can be in that same row or column. This is one of the most powerful intermediate techniques.
Applying Confinement
After initial eliminations, check each region's remaining cells. If region A's valid cells are all in column 4, then column 4 belongs to region A. Eliminate column 4 from consideration for all other regions. This can dramatically reduce options and trigger cascading placements.
Mutual Confinement
Sometimes two regions are each confined to a pair of rows. For example, if region A must be in row 2 or row 5, and region B must also be in row 2 or row 5, then those two rows are 'claimed' by these regions. No other region can place a queen in rows 2 or 5. This advanced version of confinement can break open the hardest puzzles.