A sudoku solver for 3x3, 4x4 and 5x5 boards aimed for speed using the backtracking method with heuristics
Can solve the hardest 3x3 grids in under 30ms
4x4 and 5x5 grids between 150ms to 40s depending on difficulty (empty slots and positioning)
Input format of the sudoku grid is as follows in .txt file
Empty cells can be x or 0 and don't forget to put the size of the grid on top
3
x x x | x x x | x x x
x 1 x | 6 2 x | x 9 x
x x 2 | x x 9 | 3 1 x
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x x 4 | x x 6 | x 8 x
x x 8 | 7 x 2 | 1 x x
x 3 x | 8 x x | 5 x x
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x 6 9 | 1 x x | 4 x x
x 8 x | x 7 3 | x 5 x
x x x | x x x | x x x
(Evil puzzle from www.websudoku.com)
5
1 4 23 x 12 | 3 x x 14 11 | x 17 25 x 22 | x 16 9 13 20 | x x x x 24
10 x x 3 x | 9 x 15 2 x | 21 x 11 x 5 | x 8 1 25 x | x 7 x x 14
x 11 22 8 x | x 19 x 12 17 | 13 x 2 x x | 23 14 3 x x | x x x x 5
20 x x 16 7 | x x 25 13 1 | x 14 19 24 x | 5 x x x x | x x 8 x x
x 25 5 13 2 | x 6 21 16 x | 9 23 x x x | x x x x 17 | x 12 11 x 10
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9 6 21 x x | 19 7 x x 22 | 4 3 8 13 x | 2 x x 24 23 | 16 1 x 14 x
7 x x 23 x | x 1 x x 14 | x 21 x 6 16 | 12 19 x 15 10 | x 4 x 13 11
x x x x x | 5 17 9 10 24 | 23 x x x 14 | 25 x x 21 8 | 2 x 15 x x
x x x x x | x 16 x 4 25 | 10 11 x x x | x 3 14 x x | x 23 x 19 7
x 13 x x 19 | 15 x 11 23 x | 22 20 x 18 x | x x 7 x x | 6 x 10 24 8
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x 8 x x x | x x x 9 3 | x 12 x 23 x | x 1 22 x x | x x x 5 x
24 2 11 x x | 12 25 17 x x | x 7 x 4 x | x x 15 8 x | x x x x 16
19 21 12 x x | x x x x x | x x 18 x x | x x x x x | x x 13 9 4
6 x x x x | x 22 14 x x | x 15 x 25 x | x x 23 17 4 | x x 18 12 21
x 18 x x x | x x 1 6 x | x 22 x 5 x | 7 21 x x x | x x x 25 x
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15 17 9 x 13 | x x 4 x x | x 16 x 11 23 | x 24 12 x 3 | 22 x x 8 x
16 7 x 6 x | x x 12 11 x | x x x 3 19 | 17 2 x 4 x | x x x x x
x x x x 4 | 17 3 x x 2 | 12 x x x 24 | 9 6 20 18 1 | x x x x x
11 3 x 19 x | 14 23 x 24 9 | 6 25 x 20 x | 13 x x 5 x | x 16 x x 18
x 12 x 18 24 | 6 13 x x 20 | x 9 21 17 15 | 8 x x 23 11 | x x 3 4 2
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2 x 16 4 x | 1 x x x x | x x x 21 8 | x 7 5 22 x | 24 13 12 10 x
x x 24 x x | x x x x 21 | x 4 12 1 x | 16 20 10 x x | 18 25 x x 23
18 x x x x | x x 8 19 10 | x x 6 x 7 | 15 17 x 1 x | x 2 14 20 x
13 x x 1 x | x 4 18 15 x | 5 x 24 x 17 | x 23 19 x 14 | x 6 x x 3
22 x x x x | 23 12 24 17 x | 16 x 14 10 x | 6 25 x x 21 | 4 x 9 15 1
(5x5 Sudoku puzzle from www.menneske.no/sudoku/5/eng/)
Speed improvements to come