PlaySudoku.us
Expert · Puzzle #493
7
5
8
1
8
7
9
5
4
9
8
6
3
1
3
9
5
1
8
4
5
4
2
3
7
"In chess, as in life, a man is his own most dangerous opponent." — Vasily Smyslov
"In chess, as in life, a man is his own most dangerous opponent." — Vasily Smyslov
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.