Sudoku strategies explained with graphics

Strategies


Overview Singles Naked Pairs Naked Triples Hidden Pairs Hidden Triples Naked Quads Hidden Quads Pointing Pair Pointing Triple Box Reduction X-Wing Finned X-Wing Sashimi Finned X-Wing Franken X-Wing Finned Mutant X-Wing Skyscraper Chute Remote Pairs Simple Coloring Y-Wing W-Wing Swordfish Finned Swordfish Sashimi Finned Swordfish Franken Swordfish Mutant Swordfish Finned Mutant Swordfish Sashimi Finned Mutant Swordfish Sue De Coq XYZ-Wing X-Cycle Bi-Value Universal Grave XY-Chain 3D Medusa Jellyfish Jellyfish Jellyfish Avoidable Rectangle Unique Rectangle Hidden Unique Rectangle WXYZ-Wing Firework Subset Exclusion Empty Rectangle Sue De Coq Extended SK Loop Exocet Almost Locked Sets Alternating Inference Chain Digit Forcing Chains Nishio Forcing Chains Cell Forcing Chains Unit Forcing Chains Almost Locked Sets Forcing Chain Death Blossom Pattern Overlay Bowman Bingo



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Hidden Pairs


If two candidates can be found in only the same two Cells of a region (Row, Column or Square), then one of these candidates is the solution for one of these Cells and the other candidate is the solution for the other Cell.

Hence all other candidates can be deleted from these two Cells.


hidden pairs

In the example above candidates 2 and 7 are only allowed in Cells G7 and G9 of Row "G". If candidate 2 is the solution in G7, then candidate 7 must be the solution in G9. Conversely, if candidate 2 is the solution in G9, then candidate 7 must be the solution in G7. Hence Cells G7 and G9 must have 2 or 7 as solution; all other candidates can be deleted from G7 and G9.



You can practice this strategy by installing the free SudokuCoach application on your Android™ device.

Get it on Google Play

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