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



XYZ-Wing


If a "Three-Value" Cell can see two other "Bi-Value" Cells that contain different combinations of the candidates of the first Cell, then the candidate common to the two "Bi-Value" Cells can not be the solution in any Cell that "sees" these three Cells.

Indeed, the "Three-Value" Cell and the two "Bi-Value" Cells form a group of three Cells with exactly three possible candidates, so their solution each contain one of the three candidates, in particular the "common" candidate. Hence the "common" candidate can not be the solution in any Cell that sees the three Cells.


XYZ-Wing

In the above example if candidate 1 were the solution in J3, then there would be only two possible candidates left (3 and 7) for three cells, which is not possible.



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

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