Sudoku Strategies
Take your sudoku skills to the next level with advanced techniques used by expert solvers. Master these strategies to conquer even the hardest puzzles.
Beyond Basic Solving
Once you've mastered the fundamentals of sudoku, you'll encounter puzzles that require more sophisticated techniques. These advanced strategies will help you tackle hard and expert-level puzzles with confidence.
When to Use Advanced Strategies
If you've scanned the entire puzzle and can't find any cells where a single number fits, it's time to apply these advanced techniques. They help you eliminate candidates and reveal hidden solutions.
Candidate Elimination Techniques
Naked Pairs
When two cells in the same row, column, or box contain only the same two candidates, those numbers can be eliminated from all other cells in that unit. For example, if two cells both contain only {3,7}, no other cell in that row can contain 3 or 7.
Hidden Singles
A hidden single occurs when a number can only go in one cell within a row, column, or box, even if that cell has multiple candidates. Look for numbers that appear as a candidate in only one cell of a unit.
Naked Triples
Similar to naked pairs, but with three cells containing only three candidates between them. These three numbers can be eliminated from all other cells in that unit.
Pointing Pairs
When a candidate in a box exists only in a single row or column, that candidate can be eliminated from the rest of that row or column outside the box.
Advanced Pattern Recognition
X-Wing Technique
The X-Wing is one of the most powerful advanced strategies. It occurs when a candidate appears exactly twice in two different rows, and those candidates are in the same columns. You can eliminate that candidate from all other cells in those columns.
- Step 1: Find a candidate that appears exactly twice in a row
- Step 2: Find another row where the same candidate appears twice in the same columns
- Step 3: Eliminate that candidate from other cells in those two columns
Swordfish Technique
Swordfish is an extension of X-Wing using three rows and three columns instead of two. When a candidate appears 2-3 times in three rows and those appearances align to exactly three columns, eliminate that candidate from other cells in those columns.
XY-Wing
An XY-Wing involves three cells: a pivot cell with two candidates (XY) and two pincer cells that share one candidate each with the pivot (XZ and YZ). Any cell that sees both pincers cannot contain Z.
Expert Solving Tips
- Use Pencil Marks: Write small candidate numbers in each cell to track possibilities
- Scan Systematically: Check each number 1-9 across the entire grid before moving on
- Focus on Constrained Areas: Boxes, rows, or columns with fewer empty cells are easier to solve
- Chain Techniques: For the hardest puzzles, learn forcing chains and coloring methods
- Practice Regularly: Advanced techniques become intuitive with consistent practice
Pro Tip: Bifurcation
As a last resort, you can use "trial and error" - pick a cell with two candidates, assume one is correct, and follow the logic. If you reach a contradiction, the other candidate must be correct. Use this sparingly!
Related Articles
Practice Makes Perfect
Apply these advanced strategies in Sudoku Slash! Choose expert difficulty and put your skills to the test.
Start Practicing