Medium XV Sudoku
Ready to sharpen your skills? Medium XV Sudoku puzzles introduce interactions between the variant constraint and classic Sudoku techniques. You'll need to combine both skill sets to progress.
What to expect at Medium level
Medium XV Sudoku puzzles require you to combine the variant constraint with standard Sudoku deduction - Naked pairs, hidden singles, and unit scans. The constraint is more tightly woven into the grid, so you'll need to think a few steps ahead.
Best suited for players comfortable with Easy XV Sudoku who want to build their pattern recognition.
Difficulty overview
About XV Sudoku
XV Sudoku (also called Ten-Five Sudoku) places X and V markers between adjacent cells. An X means the two cells sum to 10; a V means they sum to 5. Many XV puzzles use the negative constraint: the absence of a marker guarantees the pair neither sums to 10 nor to 5. Combined with standard Sudoku, this provides very tight constraints across the grid.
Solving Techniques for Medium Level
| Technique | Description | Level |
|---|---|---|
| Negative Constraint | Where no X or V appears between adjacent cells, their sum is neither 10 nor 5. This eliminates (1,9), (2,8), (3,7), (4,6) for X and (1,4), (2,3) for V. | Beginner |
| Sum Pair Enumeration | List all digit pairs that sum to 10 (for X) or 5 (for V), then use row/column placement to identify which pair must occupy each marked pair. | Beginner |
| Marker Chain Logic | Multiple consecutive X and V markers in a row form a sum chain — enumerate valid assignments for the entire chain simultaneously. | Intermediate |
Master these, then take on Hard Killer Sudoku to learn Advanced techniques.