
Mutant Swordfish 

A Mutant Swordfish is a swordfish that is expanded beyond just rows and columns. Where a Swordfish is 3 rows (or columns) that have candidates in only 3 columns (or rows), a Mutant Swordfish is three of any kind of unit that have candidates only in three different units. The primary units can be rows, columns, boxes, or any combination, and the secondary units can be any as well. Then, any of the candidate in question that is in a secondary unit, and not in any of the primary units, can be eliminated.
Consider the example on this page. The primary units are column 1, row 4, and the bottommiddle box. All the 9's in these units are highlighted. Now, notice that all of these 9's can be found in column 5, row 8, and the middleleft box, which are the secondary units. Thus, since three units contain 9's Only in three different units, we can eliminate all other 9's found in column 5, row 8, and the middleleft box. These eliminations are highlighted in green.
Note that the candidate in question should never be found in cells that intersect 2 or more different primary units.
Sudoku Snake gives Mutant Swordfish a skill value of 500.






