Expand description
Sudoku puzzle solver and generator library.
Sudokugen can find a solution to a valid puzzle using a mixture of basic strategies and brute force. It can also generate new minimal puzzles. This library was built as a rust learning project for myself.
§How to use Sudokugen
Sudokugen uses two structures to parse, manipulate and display a sudoku, a board and puzzle. The Board structure allows you to parse a board from a string, display it and try to solve it. The Puzzle structure contains the information relevant for a new puzzle, the initial board and it’s solution.
You can parse a board from a string:
use sudokugen::Board;
let board: Board = "
. . . | 4 . . | 8 7 .
4 . 3 | . . . | . . .
2 . . | . . 3 | . . 9
---------------------
. . 6 | 2 . . | . . 7
. . . | 9 . 6 | . . .
3 . 9 | . 8 . | . . .
---------------------
. . . | . . . | . 4 .
8 7 2 | 5 . . | . . .
. . . | 7 2 . | 6 . .
".parse().unwrap();After it’s parsed you can solve it using the Board::solve function:
board.solve().unwrap();
assert_eq!(
board,
"695412873413879526287653419146235987728946135359187264561398742872564391934721658"
.parse()
.unwrap()
);Finally you can generate new puzzles using Puzzle::generate, when doing this you must specify what size of puzzle do you want to generate, BoardSize makes that easy.
use sudokugen::{Puzzle, BoardSize};
let puzzle = Puzzle::generate(BoardSize::NineByNine);
println!("Puzzle\n{}", puzzle.board());
println!("Solution\n{}", puzzle.solution());Which will print something like this:
> Puzzle
> . . . . . . . 6 .
> . 1 7 . 4 . . 9 .
> . . . . 9 . 5 3 .
> . . 5 . 7 2 8 . .
> 1 . . . . 8 4 5 .
> . 4 . 9 . . . . .
> 8 7 9 1 2 . . . .
> 4 5 . 8 . . . . .
> . . . . . . . . .
>
> Solution
> 9 2 3 5 8 1 7 6 4
> 5 1 7 6 4 3 2 9 8
> 6 8 4 2 9 7 5 3 1
> 3 6 5 4 7 2 8 1 9
> 1 9 2 3 6 8 4 5 7
> 7 4 8 9 1 5 6 2 3
> 8 7 9 1 2 6 3 4 5
> 4 5 6 8 3 9 1 7 2
> 2 3 1 7 5 4 9 8 6§Crate Layout
This crate is divided in three modules. board contains the tools needed to parse, manipulate and print
a puzzle and its individual cells. solver extends board::Board with the board::Board::solve function and solver::generator contains
the Puzzle structure and it’s static Puzzle::generate function.
§Puzzle quality
Grading puzzles is beyond the scope of this crate. The reason behind it is that grading puzzles correctly, requires solving them like a human would and some of the more complex techniques to solve a puzzle like a human would require a lot of computations that do not always payoff performance-wise.
That being said, the generated puzzles consistently have between 22 and 26 clues making them likely on the harder side of most generally available puzzles.
§Is it fast?
The quick answer is, it depends on your use case. The Board::solve function is optimized to be
decently fast for a 9x9 sudoku puzzle, in my 2017 MacBook Pro it takes an average of 300μs
to solve a difficult puzzle, that is around 3000 puzzles per second.
The Puzzle::generate function is less optimized and makes heavy usage of Board::solve without trying to
re-use repeated computations, as such it’s much slower clocking at about 18ms to generate
a new puzzle in my benchmarks.
You can run your own benchmarks with cargo bench