How to Find & Solve the Swordfish Technique in Sudoku
The Swordfish is one of the premier advanced deduction patterns in Sudoku. By coordinating 3 rows that lock a candidate into 3 shared columns, you can wipe out false candidates across multiple houses at once.
Hands-On Swordfish Elimination
In Rows 1, 5, and 9, candidate 6 only appears within Columns 2, 5, and 8. Because digit 6 is forced into these three columns, execute the elimination to prune stray 6s from R3C2 and R7C5!
The 3-Step Swordfish Protocol
- Locate 3 Base Rows: Find three rows where a particular candidate appears in only 2 or 3 cells each.
- Verify 3-Column Alignment: Ensure that the candidate cells across all three rows fall entirely within the exact same three columns.
- Eliminate Vertically: Eliminate that candidate from every other cell in those three columns.
Frequently Asked Questions
What is a Swordfish in Sudoku? ▼
A Swordfish is an expert fish solving technique that extends the X-Wing to three rows and three columns. When a specific candidate number appears in at most three cells in each of three different rows, and all those cells are contained within the exact same three columns, the candidate can be eliminated from all other cells in those three columns.
Does every row need all three cells filled in a Swordfish? ▼
No! Each of the three rows can contain either 2 or 3 candidate cells, as long as across all three rows, the candidates are strictly confined to the exact same three columns.
How does a Swordfish compare to an X-Wing or Jellyfish? ▼
An X-Wing spans a 2×2 grid (2 rows and 2 columns). A Swordfish spans a 3×3 grid (3 rows and 3 columns). A Jellyfish spans a 4×4 grid (4 rows and 4 columns). They all follow the exact same fish elimination principle.
Conquer Master-Tier Puzzles with Swordfish
Swordfish is the ultimate fish pattern before 4-line Jellyfish. Test your master solving logic on our Evil Sudoku or Expert Sudoku boards, or review earlier fish patterns.