The rules of four sudoku variants, each with a sample puzzle from the book's free sample where the sample has one. Each puzzle shown was checked by the solver and has exactly one solution.
Fill every row, column and 3x3 box with the digits 1 to 9. Both main diagonals (shaded grey) must also hold 1 to 9 once each.
| 7 | 6 | 1 | ||||||
| 4 | 9 | 8 | 3 | 1 | 2 | |||
| 7 | 2 | |||||||
| 4 | 6 | 1 | ||||||
| 7 | 3 | 1 | 4 | |||||
| 1 | 9 | 5 | 2 | |||||
| 2 | 9 | |||||||
| 1 | 7 | 6 | ||||||
| 2 | 5 | 3 |
Fill every row, column and 3x3 box with the digits 1 to 9. The four extra 3x3 windows must also hold 1 to 9 once each.
Fill every row, column and 3x3 box with the digits 1 to 9. No two cells a chess knight's move apart may hold the same digit.
Fill every row, column and 3x3 box with the digits 1 to 9. No two cells that touch, diagonals included, may hold the same digit.
The solver and its licence are in the GitHub repository.
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