Sudoku Solving Techniques

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Jelly Fish

Jelly Fish

For a real hair-pulling screamer that’s still logical, not a lot beats a Jelly-Fish – except the fabled Squirm-Bag which uses five rows and columns. Jelly-Fish is the fourfold extension of X-Wing and Sword-Fish.

In this example number 4 is being Jelly-Fished!

Fig. 14.1

As you can see, of the 16 nodes involved, only 11 actually contain a 4.

Generalizing X-Wing

X-Wing is not restricted to rows and columns. We can also extend the idea to boxes as well. If we generalise the rule in chapter 14 above we get:

When there are

only 2 candidates for a value, in each of 2 different units of the same kind,
and these candidates lie also on 2 other units of the same kind,

then all other candidates for that value can be eliminated from the latter two units.

Now we have 6 combinations: Starting from 2 rows and eliminating in 2 columns

Starting from 2 columns and eliminating in 2 rows
Starting from 2 boxes and eliminating in 2 rows
Starting from 2 boxes and eliminating in 2 columns
Starting from 2 rows and eliminating in 2 boxes
Starting from 2 columns and eliminating in 2 boxes

Classic X-Wing
Classic X-Wing
Same effect as line/box reduction
Same effect as line/box reduction
Same effect as pointing pairs

Same effect as pointing pairs

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