Lesson #11: The Sudoku Swordfish: An X Wing Variant with a 3x3 Rectangle

The Swordfish pattern will sometimes appear in a medium to advance level sudoku puzzle. You can usually spot it at the early stages of solving a sudoku puzzle. Please review the x wing pattern first before moving on to the swordfish. The x wing is a 2x2 rectangle, the swordfish is a 3x3 rectangle. Both have the same logic, if one cell is true, then the others in the same row or column cannot be true, and if you follow the logic around the rectangle you can then eliminate all the other same candidates in the row or column. The concept is a little more complicated than the x wing, but the logic is the same. You might want to watch this lesson more than once ;)