133 lines
3.4 KiB
Markdown
133 lines
3.4 KiB
Markdown
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Puzzle Solver [![Version][version-img]][version-url] [![Status][travis-ci-img]][travis-ci-url]
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=============
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About
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-----
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Solve logic puzzles by simply describing the puzzle's rules as
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constraints. This is suitable for solving puzzles with integer
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variables such as Sudoku, Killer Sudoku, Kakuro, and Zebra puzzles.
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The puzzle solver maintains a list of candidates for each puzzle
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variable. It solves puzzles by eliminating candidates that would lead
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to a contradiction and taking any forced moves that were exposed in
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the process. This is repeated until it gets stuck, whereupon it will
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perform a backtracking search -- it will assign a single variable and
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continue with the candidate elimination step again.
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Examples
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--------
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A few example programs are provided in the `tests/` directory:
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* _Hidato_ - https://en.wikipedia.org/wiki/Hidato
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* _Kakuro_ - https://en.wikipedia.org/wiki/Kakuro
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* _Killer Sudoku_ - https://en.wikipedia.org/wiki/Killer_sudoku
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* _Magic Square_ - https://en.wikipedia.org/wiki/Magic_square
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* _N-queens problem_ - https://en.wikipedia.org/wiki/Eight_queens_puzzle
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* _Send More Money_ - https://en.wikipedia.org/wiki/Verbal_arithmetic
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* _Sudoku_ - https://en.wikipedia.org/wiki/Sudoku
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* _Sujiko_ - https://en.wikipedia.org/wiki/Sujiko
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* _Zebra puzzle (Einstein's riddle)_ - https://en.wikipedia.org/wiki/Zebra_Puzzle
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To clone this repository, run:
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```sh
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git clone https://github.com/wangds/puzzle-solver.git
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```
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Then build the library and run the test programs using Cargo.
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```sh
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cargo test --test sudoku -- --nocapture
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```
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Basic Usage
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-----------
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We will demonstrate how to solve the equation "SEND + MORE = MONEY".
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Add Puzzle Solver as a dependency to your project's Cargo.toml:
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```toml
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[dependencies]
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puzzle-solver = "0.2"
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```
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Import the library in your project, e.g.:
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```rust
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extern crate puzzle_solver;
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use puzzle_solver::Puzzle;
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```
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First, we create a puzzle object and the 8 puzzle variables
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`(S,E,N,D,M,O,R,Y)`.
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```rust
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let mut puzzle = Puzzle::new();
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let vars = puzzle.new_vars_with_candidates_1d(8, &[0,1,2,3,4,5,6,7,8,9]);
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let (s, e, n, d) = (vars[0], vars[1], vars[2], vars[3]);
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let (m, o, r, y) = (vars[4], vars[5], vars[6], vars[7]);
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```
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All eight puzzle variables have been initialised to be any number
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between 0 and 9. However, we know that the numbers are not allowed to
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begin with zero, so we remove the choices of S = 0 and M = 0.
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```rust
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puzzle.remove_candidates(s, &[0]);
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puzzle.remove_candidates(m, &[0]);
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```
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We add the constraint that the variables should be all different:
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```rust
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puzzle.all_different(&vars);
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```
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We write the equation as another puzzle constraint:
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```rust
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puzzle.equals(
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(1000 * s + 100 * e + 10 * n + d) + (1000 * m + 100 * o + 10 * r + e),
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10000 * m + 1000 * o + 100 * n + 10 * e + y);
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```
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And we solve!
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```rust
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let solution = puzzle.solve_any().expect("solution");
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assert_eq!(solution[o], 0);
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assert_eq!(solution[m], 1);
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assert_eq!(solution[y], 2);
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assert_eq!(solution[e], 5);
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assert_eq!(solution[n], 6);
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assert_eq!(solution[d], 7);
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assert_eq!(solution[r], 8);
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assert_eq!(solution[s], 9);
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```
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Documentation
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-------------
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* [Documentation][documentation].
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Author
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------
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David Wang
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[documentation]: https://docs.rs/puzzle-solver/
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[travis-ci-img]: https://travis-ci.org/wangds/puzzle-solver.svg?branch=master
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[travis-ci-url]: https://travis-ci.org/wangds/puzzle-solver
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[version-img]: https://img.shields.io/crates/v/puzzle-solver.svg
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[version-url]: https://crates.io/crates/puzzle-solver
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