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
Network flow algorithms can solve special classes of Sudoku more efficiently than general backtracking.
Network flow algorithms can solve special classes of Sudoku more efficiently than general backtracking.
The 'Skyscraper' technique links two X-Wing candidates via a shared column — advanced but powerful on expert grids.
The 'Skyscraper' technique links two X-Wing candidates via a shared column — advanced but powerful on expert grids.