Anti-Diagonal Sudoku
A fascinating Sudoku variation where each main diagonal contains only three different digits
Anti-Diagonal Sudoku Puzzle is a very nice Sudoku variation. In the Diagonal Sudoku, all the numbers coming on the main diagonals are unique and have to be only 1 to 9. However, in Anti-Diagonal Sudoku, 3 numbers on the main diagonals are repeated thrice.
To solve an Anti-Diagonal Sudoku, one has to concentrate on the diagonals and try to find out the three numbers that will be repeated on the diagonals.
The central most cell contains the digit which will be repeated thrice on both the diagonals. The other two numbers will be different for different main diagonals. So it's easier to find this cell and then proceed to find the other numbers on the diagonals.
Rules of Anti Diagonal Sudoku Puzzle
Place a digit from 1 to 9 into each of the empty cells so that each digit appears exactly once in each row, column, and 3×3 outlined box. Additionally, every main/marked diagonal contains only 3 different numbers (e.g. 1, 4, 6).
Why Solve Anti-Diagonal Sudoku?
- Experience a unique twist on Diagonal Sudoku with repeated digits on the diagonals.
- Develop diagonal-focused reasoning — a different spatial skill from standard Sudoku.
- Learn to identify the central cell that reveals the digit repeated on both diagonals.
- Master the logic of three repeated numbers across the two main diagonals.
- Perfect for experienced Sudoku solvers seeking a fresh challenge.
- A great entry point into Sudoku variants with unique constraints.
Key Techniques for Solving Anti Diagonal Sudoku
- Find the central cell — the digit in the center of the grid appears on both diagonals. This is your starting point.
- Identify the three diagonal digits — each main diagonal contains only three unique digits. Work out which ones they are.
- Apply standard Sudoku logic — always apply row, column, and box eliminations alongside the diagonal rule.
- Look for repeated patterns — the three digits on the diagonal will appear multiple times across the diagonal cells.
- Use elimination on the diagonal — once you place a digit on the diagonal, it cannot appear on the other diagonal. Here, the central digit is an exception, as it will be used on both diagonals.
- Check your diagonal sets — verify that each diagonal contains exactly three different digits.
🧩 Anti Diagonal Sudoku Puzzles
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Frequently Asked Questions
What is Anti Diagonal Sudoku?
Anti Diagonal Sudoku is a variation of Classic Sudoku where the digits on the two main diagonals are not unique. Instead, each main diagonal contains exactly three different digits that repeat across the diagonal. This creates a unique constraint that requires a different solving approach than standard Sudoku.
How is Anti Diagonal Sudoku different from Diagonal Sudoku?
In Diagonal Sudoku, the digits on the main diagonals must be unique (1-9 exactly once). In Anti Diagonal Sudoku, the diagonals contain only three different digits repeated across the diagonal. This makes the puzzle more constrained in a different way, requiring a different logical approach.
What is the central cell trick?
The central cell of the grid (row 5, column 5) is the intersection of both main diagonals. Therefore, the digit in this cell must appear on both diagonals. Since each diagonal has only three different digits, the central cell's digit is one of the three for both diagonals, making it a powerful starting point for solving.
Do I need to know how to solve Classic Sudoku first?
Yes — Anti Diagonal Sudoku is built on the foundation of Classic Sudoku. A solid understanding of standard Sudoku rules and basic solving techniques is essential before attempting this variant. If you are new to Sudoku, visit our Classic Sudoku page first.
Where can I find more Sudoku variants?
The Sudoku Variations Main Page is the central index for all Sudoku variant types available on Fun With Puzzles. It covers a wide range of constraint-based variants and is the best place to discover new Sudoku challenges.
⚠️ The diagonals hold the key — can you solve the Anti Diagonal challenge? Try today's Daily Challenge!
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