Sudoku Swordfish Strategy: Master This Proven 3-Step Method (with Diagrams) - SudokuPuzzles.net

The Swordfish technique is an advanced Sudoku solving method that extends the concept of the X-Wing pattern to three rows and columns. It's one of the most powerful fish patterns in Sudoku and can help you solve even the most challenging puzzles.

What is the Swordfish Technique?

The Swordfish technique is a pattern recognition method that works when a specific digit appears in exactly three rows (or columns) and exactly three columns (or rows). This creates a pattern that allows you to eliminate candidates from other cells.

Think of it as an extension of the X-Wing technique:

• X-Wing: 2 rows × 2 columns
• Swordfish: 3 rows × 3 columns

How the Swordfish Pattern Works

For a Swordfish pattern to be valid, you need:

1. A specific digit that appears as a candidate in exactly three rows
2. These three rows must share exactly three columns
3. The digit must appear in exactly three cells total across these rows and columns

When this pattern exists, you can eliminate the digit as a candidate from all other cells in the three columns (or rows, depending on your perspective).

Step-by-Step Swordfish Identification

Step 1: Choose a Target Digit

Start by selecting a digit that appears frequently in your puzzle. Look for digits that have candidates in multiple rows and columns.

Step 2: Find Three Rows with the Digit

Identify three rows where your target digit appears as a candidate. The digit should appear in exactly three rows total.

Step 3: Check Column Alignment

Verify that these three rows share exactly three columns where the digit appears. The pattern should form a 3×3 grid of possible positions.

Step 4: Apply the Elimination

If the pattern is valid, eliminate the target digit from all other cells in the three columns that are not part of the Swordfish pattern.

Swordfish Example

Let's say we're looking for digit 7 in a Swordfish pattern: