PlaySudoku.us
Hard · Puzzle #657
8
4
9
7
5
1
8
1
6
2
7
2
3
6
1
3
8
7
4
9
1
9
6
8
4
6
8
Donald Knuth's "dancing links" algorithm — published in 2000 — is one of the fastest ways to solve Sudoku by computer.
Donald Knuth's "dancing links" algorithm — published in 2000 — is one of the fastest ways to solve Sudoku by computer.
Always update pencil marks immediately after placing a digit — stale marks cause almost all solving errors.
Always update pencil marks immediately after placing a digit — stale marks cause almost all solving errors.