What is what to do in sudoku when stuck?

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What to Do When You're Stuck in Sudoku

Getting stuck in Sudoku is a common experience. Here's a breakdown of techniques to help you break through:

• Review the Basics: Start by ensuring you haven't overlooked any obvious errors. Are there any duplicate numbers in a row, column, or 3x3 box? Double-check your work! Sometimes a fresh look is all you need.
• Scanning: This involves focusing on a single number (1-9) and systematically scanning the grid to identify possible locations for that number. Look for rows, columns, or boxes where the number is already present, eliminating those possibilities. Learn more about scanning.
• Marking Candidates (Pencil Marks/Notations): If you haven't already, meticulously mark all the possible candidates (potential numbers) for each empty cell. This is crucial for more advanced techniques. Learn the importance of candidate%20marking.
• Hidden Singles: A hidden single is a number that is a candidate in only one cell within a row, column, or box, even if other candidates exist in that cell. Find more on hidden%20singles.
• Naked Singles: This is the simplest technique. If a cell has only one possible candidate marked, that candidate must be the correct number for that cell. Discover naked%20singles.
• Locked Candidates (Pointing Pairs/Triples): When all the candidates for a particular number within a box are confined to a single row or column, you can eliminate that candidate from the same row or column outside of that box. Deep dive into locked%20candidates.
• Elimination Techniques (Box/Line Reduction): Similar to locked candidates, this involves identifying candidate placements that restrict a number to only one row or column within a box. Understand box%20line%20reduction.
• Naked Pairs/Triples/Quads: Look for two/three/four cells within the same row, column, or box that contain only the same two/three/four candidates. This allows you to eliminate those candidates from other cells in that row, column, or box. Explore naked%20pairs%20triples.
• Hidden Pairs/Triples/Quads: Look for two/three/four candidates that only appear in two/three/four cells within a row, column, or box. This allows you to eliminate other candidates from those cells. Dig into hidden%20pairs%20triples.
• X-Wing: This is an advanced technique that involves identifying two rows or columns where a specific number appears as a candidate in only two cells, and those cells align to form a rectangle. You can then eliminate that candidate from the cells in the corresponding columns/rows that intersect the rectangle. Grasp the x-wing%20technique.
• Swordfish: Similar to X-Wing, but involves three rows or columns. Learn the swordfish%20technique.
• XY-Wing: Another advanced technique involving three cells (X, Y, and Z) that have only two candidates each. If X has candidates XY, Y has candidates YZ, and Z has candidates XZ, and X and Z see a common cell, then you can eliminate the common candidate between X and Z from that common cell. Study the xy-wing%20technique.
• Y-Wing: An XY-Wing variation, see details Y-Wing%20Technique.
• AIC (Alternative Inference Chain): These very complex techniques are used to solve the hardest puzzles. It involves looking for chain of numbers and relations, read more about AIC%20Technique.
• Trial and Error (Last Resort): If all else fails, you can try making a temporary guess in one of the candidate cells. Follow the implications of your guess. If it leads to a contradiction (e.g., a duplicate number in a row), you know that the guess was wrong, and you can eliminate that candidate. Only use this as a last resort!

Remember, patience and persistence are key to solving Sudoku puzzles. Good luck!