HodokuRevisited

Techniques / Single Digit Patterns

Turbot Fish

Hard

Strong link, weak link, strong link on one digit; the two ends cannot both be false.

Pick a digit. Find a unit where it has exactly two candidates (a strong link between A and B), another strong link between C and D, and connect them with a weak link: B and C see each other. If A is false then B is true, which makes C false, which makes D true. So at least one of A and D is true.

Any cell that sees both A and D cannot hold the digit. Skyscrapers, 2-String Kites and Empty Rectangles are special shapes of the Turbot Fish, which is why the solver treats them as separate, simpler names.

Notation

Turbot Fish: 4 can be removed from r8c8. chain: 4 in r6c8 → 4 in r5c9 → 4 in r5c1 → 4 in r8c1.

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Turbot Fish: 4 can be removed from r8c8. chain: 4 in r6c8 → 4 in r5c9 → 4 in r5c1 → 4 in r8c1.

pattern removed solid: strong link, dashed: weak link

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