PlaySudoku.us
Hard · Puzzle #231
1
4
5
7
9
6
1
2
8
3
9
5
7
8
9
4
5
8
2
9
6
6
2
8
7
6
2
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.
The hardest Sudoku puzzles require techniques equivalent to propositional logic — the same foundation used in computer proofs.
A Sudoku grid is a special case of a Latin square: a 9×9 grid where each symbol appears exactly once in each row and column.
A Sudoku grid is a special case of a Latin square: a 9×9 grid where each symbol appears exactly once in each row and column.