PlaySudoku.us
Hard · Puzzle #19
6
5
9
9
6
4
4
2
7
8
4
5
7
2
5
6
2
3
1
3
9
5
1
6
2
6
9
4
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.
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.