Sudoku solver in F#. This version currently uses exceptions for control flow, which is frowned upon in the F# world. Next I'll attempt to change it to use a mondaic Result construct.
type Cell = Known of int | Possible of Set<int>
type Grid = Cell[,]
To attempt to solve a problem, an initial board state and a makeMove function are supplied. The makeMove function sets a value in a cell to a Known integer and updates all the Possible sets of integers for cells affected by the particular game rule.
makeSudokuMove is used for standard Sudoku.
makeMiracleSudoku move is used for the Miracle Sudoku problem by Mitchell Lee.
This table shows the performance results running the tests a single time in Release on my Huaweii Matebook X Pro.
For all tests the smaller time is better (faster).
This compares solveGrid which visits cells from top left to bottom right
vs solveGrid2 which orders the solver by the fewest number of remaining possibilities in each cell.
| Test | Problem | solveGrid Time | solveGrid2 Time |
|---|---|---|---|
| 1 |  |
0.091504s | 0.073380s |
| 2 |  |
0.033452s | 0.026237s |
| 3 |  |
0.065200s | 0.061731s |
| 4 |  Empty Problem |
0.040063s | 0.036557 |
| 5 |  Miracle Sudoku |
15.329430s | 0.119469s |