Hard Anti-Consecutive Sudoku
1
5
2
3
9
4
4
1
5
8
3
6
7
9
8
4
2
8
1
3
1
9
5
2
6
3
7
How to play Anti-Consecutive Sudoku
Standard Sudoku rules apply. Extra rule: no two orthogonally adjacent cells (sharing an edge) may contain consecutive digits. If a cell holds 5, all four neighbours must avoid 4 and 6.
About Anti-Consecutive Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Anti-Constraints
Typical Givens
18–24
Avg. Solve (Medium)
13 min
Anti-Consecutive Sudoku (a stricter form of Non-Consecutive Sudoku) imposes the rule that no two orthogonally adjacent cells may contain consecutive integers. This variant often requires fewer given digits because the constraint alone eliminates so many candidate pairs. It is sometimes combined with Anti-King or Anti-Knight to create extremely constrained puzzles.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Global Candidate Pruning | For every filled cell, remove its ±1 neighbours from all orthogonally adjacent cells immediately. | Beginner |
| Digit 5 is Most Constrained | 5 cannot be adjacent to 4 or 6. Use this to restrict placement of 5 across the entire grid. | Intermediate |
| Chain Propagation | Placing a digit propagates constraints along rows and columns, often triggering a cascade of forced placements. | Intermediate |
| Forbidden Pair Maps | Build a map of forbidden digit pairs for each adjacent pair of cells and use it to eliminate candidates systematically. | Advanced |
Average Solve Time by Difficulty
Easy
5 min
Medium
13 min
Hard
26 min
Expert
48 min