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// Code lints #![warn(trivial_casts)] #![warn(trivial_numeric_casts)] #![warn(unreachable_pub)] #![warn(unused_import_braces)] #![warn(unused_lifetimes)] #![warn(unused_qualifications)] // Doc lints #![warn(broken_intra_doc_links)] #![warn(missing_docs)] #![warn(missing_crate_level_docs)] #![warn(invalid_codeblock_attributes)] //! This crate implements an easy-to-understand and flexible Sudoku engine. It //! supports the following key features: //! //! * Parsing and printing Sudoku //! * Checking validity of Sudoku and solutions according to standard rules as //! well as some common variants //! * Injection of custom constraints //! * Solving Sudoku using a perfect backtracking algorithm //! * Generating Sudoku with a possibility to specify a custom solver that has //! to be able to solve the result, thus controlling the difficulty //! //! Note in this introduction we will mostly be using 4x4 Sudoku due to their //! simpler nature. These are divided in 4 2x2 blocks, each with the digits 1 //! to 4, just like each row and column. //! //! # Parsing and printing Sudoku //! //! See [SudokuGrid::parse] for the exact format of a Sudoku code. //! //! Codes can be used to exchange Sudoku, while pretty prints can be used to //! display a Sudoku in a clearer manner. An example of how to parse and //! display a Sudoku grid is provided below. //! //! ``` //! use sudoku_variants::SudokuGrid; //! //! let grid = //! SudokuGrid::parse("2x2;2, ,3, , ,1, , ,1, , ,4, ,2, ,3").unwrap(); //! println!("{}", grid); //! ``` //! //! # Checking validity of Sudoku //! //! To check validity, an instance of [Sudoku] not only contains the numbers //! (stored in a [SudokuGrid]), but also some constraint which specifies the //! rules. For classic Sudoku rules, //! [DefaultConstraint](constraint::DefaultConstraint) can be used. //! //! It is possible to check an entire Sudoku, individual cells, or potential //! changes to individual cells that do not require changing the Sudoku's //! state. An example of the former is provided below. //! //! ``` //! use sudoku_variants::Sudoku; //! use sudoku_variants::constraint::DefaultConstraint; //! //! // Some Sudoku for which it is totally unclear whether it is valid. //! let sudoku = Sudoku::parse("2x2;1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1", //! DefaultConstraint).unwrap(); //! assert!(!sudoku.is_valid()); //! ``` //! //! If you are developing an app that gives feedback to the user, it may be //! desirable to specify where they made an error. Also, sometimes checking the //! entire Sudoku is redundant, since only one cell has changed. To do this, it //! is possible to check the validity of just one cell in the grid. //! //! ``` //! use sudoku_variants::Sudoku; //! use sudoku_variants::constraint::DefaultConstraint; //! //! // A riddle posed by our app: //! // ╔═══╤═══╦═══╤═══╗ //! // ║ │ ║ │ 4 ║ //! // ╟───┼───╫───┼───╢ //! // ║ │ 4 ║ 3 │ ║ //! // ╠═══╪═══╬═══╪═══╣ //! // ║ │ 3 ║ │ ║ //! // ╟───┼───╫───┼───╢ //! // ║ │ ║ 1 │ ║ //! // ╚═══╧═══╩═══╧═══╝ //! let mut sudoku = Sudoku::parse("2x2; , , ,4, ,4,3, , ,3, , , , ,1, ", //! DefaultConstraint).unwrap(); //! //! // Some (unfortunatly wrong) user input to the top-left cell //! sudoku.grid_mut().set_cell(0, 0, 4); //! assert!(!sudoku.is_valid_cell(0, 0).unwrap()); //! ``` //! //! Similarly, it is also possible to check a singular cell with a potntial new //! entry, before changing the Sudoku, using [Sudoku::is_valid_number]. Since //! it otherwise behaves just like the example above, we will not provide //! another example. //! //! All examples above have been using the //! [DefaultConstraint](constraint::DefaultConstraint), which is actually a //! composition of [RowConstraint](constraint::RowConstraint), //! [ColumnConstraint](constraint::ColumnConstraint), and //! [BlockConstraint](constraint::BlockConstraint). Additionally to //! those three primitives, a few more common Sudoku variants' rules are //! provided, which can be combined into more exciting rule sets. Check out the //! [constraint] module for more details and instructions on how to write your //! own rules. //! //! # Solving Sudoku //! //! This crate offers a [Solver](solver::Solver) trait for structs that can //! totally or partially solve Sudoku (that is, able to solve every Sudoku with //! a unique solution or not). As a default implementation, //! [BacktrackingSolver](solver::BacktrackingSolver) is provided, which can //! solve every uniquely solveable Sudoku. //! //! To use it, first instantiate a Sudoku an then call //! [Solver.solve](solver::Solver::solve) on a backtracking //! solver (as it is a zero-sized struct, no instantiation is required). //! //! ``` //! use sudoku_variants::{Sudoku, SudokuGrid}; //! use sudoku_variants::constraint::DefaultConstraint; //! use sudoku_variants::solver::{BacktrackingSolver, Solution, Solver}; //! //! // The same Sudoku as in our previous example. //! let sudoku = Sudoku::parse("2x2; , , ,4, ,4,3, , ,3, , , , ,1, ", //! DefaultConstraint).unwrap(); //! let solution = BacktrackingSolver.solve(&sudoku); //! //! // The solution we expect: //! // ╔═══╤═══╦═══╤═══╗ //! // ║ 3 │ 1 ║ 2 │ 4 ║ //! // ╟───┼───╫───┼───╢ //! // ║ 2 │ 4 ║ 3 │ 1 ║ //! // ╠═══╪═══╬═══╪═══╣ //! // ║ 1 │ 3 ║ 4 │ 2 ║ //! // ╟───┼───╫───┼───╢ //! // ║ 4 │ 2 ║ 1 │ 3 ║ //! // ╚═══╧═══╩═══╧═══╝ //! let expected_solution_grid = //! SudokuGrid::parse("2x2;3,1,2,4,2,4,3,1,1,3,4,2,4,2,1,3").unwrap(); //! //! assert_eq!(Solution::Unique(expected_solution_grid), solution); //! ``` //! //! The backtracking solver can deal with any (correctly implemented) //! constraint and type of Sudoku. If there is no solution, it will return //! `Solution::Impossible` and if there are multiple solutions, it will reutrn //! `Solution::Ambiguous`. //! //! ## Performance improvements //! //! Using pure backtracking can be an issue regarding performance. It is //! possible to use heuristics, so-called //! [Strategies][crate::solver::strategy::Strategy] that use logic to fill some //! cells or remove some optinos. This can be much faster than pure //! backtracking, but some experimentation is required. See the //! [strategy](crate::solver::strategy) module for further information. //! //! # Generating Sudoku //! //! Probably the most interesting feature of this crate is the generation of //! random Sudoku. This is done in two steps: generating a full grid using a //! [Generator](generator::Generator) and then removing as many clues as //! possible using a [Reducer](generator::Reducer). //! //! The generator needs a solver, which helps to reduce the search space for //! valid grids, and a random number generator, for which we use the `Rng` //! trait from the [rand](https://rust-random.github.io/rand/rand/index.html) //! crate. The reducer needs the same, however its solver is used to define the //! difficulty. Essentially, the reducer will generate a puzzle that is just //! not too hard for the given solver, that is, if one more clue were removed, //! the solver would be unable to solve it. An example of generating a minimal //! puzzle (where no clues can be removed without losing uniqueness) is //! provided below. //! //! ``` //! use sudoku_variants::constraint::DefaultConstraint; //! use sudoku_variants::generator::{Generator, Reducer}; //! use sudoku_variants::solver::{BacktrackingSolver, Solution, Solver}; //! //! // new_default yields a generator/reducer with a backtracking solver and //! // rand::thread_rng() //! let mut generator = Generator::new_default(); //! let mut reducer = Reducer::new_default(); //! //! // Generate a full, 3x3 block Sudoku board with default rules. //! let mut sudoku = generator.generate(3, 3, DefaultConstraint).unwrap(); //! assert!(sudoku.is_valid()); //! //! // Remove as many clues as possible //! reducer.reduce(&mut sudoku); //! //! let unique = match BacktrackingSolver.solve(&sudoku) { //! Solution::Unique(_) => true, //! _ => false //! }; //! assert!(unique); //! ``` //! //! ## Defining a difficulty //! //! The above example removes digits as long as the resulting Sudoku is still //! uniquely solveable. This may result in some very difficult Sudoku, since it //! provides no guarantees as to *how* the Sudoku can be solved. To generate //! less difficult Sudoku, you can provide a less powerful //! [Solver](crate::solver::Solver), which has to be able to solve the reduced //! Sudoku. See the [strategy](crate::solver::strategy) module for further //! information. //! //! # Note regarding performance //! //! While generating ordinary, minimal Sudoku with this crate is doable within //! a few seconds, more complicated rule sets which result in less necessary //! clues or larger boards may result in performance issues. In any case, it is //! strongly recommended to use at least `opt-level = 2` for approximately a //! 28-fold performance improvement, even in tests that use Sudoku generation. pub mod constraint; pub mod error; pub mod generator; pub mod solver; pub mod util; #[cfg(test)] mod fix_tests; use constraint::Constraint; use error::{SudokuError, SudokuParseError, SudokuParseResult, SudokuResult}; use std::fmt::{self, Display, Error, Formatter}; /// A Sudoku grid is composed of cells that are organized into blocks of a /// given width and height in a way that makes the entire grid a square. /// Consequently, the number of blocks in a row is equal to the block height /// and vice versa. Each cell may or may not be occupied by a number. /// /// In ordinary Sudoku, the block width and height are both 3. Here, however, /// more exotic variants are permitted, for example 4x2 blocks, which would /// result in a grid like this: /// /// ```text /// ╔═══╤═══╤═══╤═══╦═══╤═══╤═══╤═══╗ /// ║ │ │ │ ║ │ │ │ ║ /// ╟───┼───┼───┼───╫───┼───┼───┼───╢ /// ║ │ │ │ ║ │ │ │ ║ /// ╠═══╪═══╪═══╪═══╬═══╪═══╪═══╪═══╣ /// ║ │ │ │ ║ │ │ │ ║ /// ╟───┼───┼───┼───╫───┼───┼───┼───╢ /// ║ │ │ │ ║ │ │ │ ║ /// ╠═══╪═══╪═══╪═══╬═══╪═══╪═══╪═══╣ /// ║ │ │ │ ║ │ │ │ ║ /// ╟───┼───┼───┼───╫───┼───┼───┼───╢ /// ║ │ │ │ ║ │ │ │ ║ /// ╠═══╪═══╪═══╪═══╬═══╪═══╪═══╪═══╣ /// ║ │ │ │ ║ │ │ │ ║ /// ╟───┼───┼───┼───╫───┼───┼───┼───╢ /// ║ │ │ │ ║ │ │ │ ║ /// ╚═══╧═══╧═══╧═══╩═══╧═══╧═══╧═══╝ /// ``` /// /// `SudokuGrid` implements `Display`, but only grids with a size (that is, /// width or height) of less than or equal to 9 can be displayed with digits /// 1 to 9. Sudoku of all other sizes will raise an error. #[derive(Clone, Debug, Eq, PartialEq)] pub struct SudokuGrid { block_width: usize, block_height: usize, size: usize, cells: Vec<Option<usize>> } fn to_char(cell: Option<usize>) -> char { if let Some(n) = cell { (b'0' + n as u8) as char } else { ' ' } } #[allow(clippy::too_many_arguments)] fn line(grid: &SudokuGrid, start: char, thick_sep: char, thin_sep: char, segment: impl Fn(usize) -> char, pad: char, end: char, newline: bool) -> String { let size = grid.size(); let mut result = String::new(); for x in 0..size { if x == 0 { result.push(start); } else if x % grid.block_width == 0 { result.push(thick_sep); } else { result.push(thin_sep); } result.push(pad); result.push(segment(x)); result.push(pad); } result.push(end); if newline { result.push('\n'); } result } fn top_row(grid: &SudokuGrid) -> String { line(grid, '╔', '╦', '╤', |_| '═', '═', '╗', true) } fn thin_separator_line(grid: &SudokuGrid) -> String { line(grid, '╟', '╫', '┼', |_| '─', '─', '╢', true) } fn thick_separator_line(grid: &SudokuGrid) -> String { line(grid, '╠', '╬', '╪', |_| '═', '═', '╣', true) } fn bottom_row(grid: &SudokuGrid) -> String { line(grid, '╚', '╩', '╧', |_| '═', '═', '╝', false) } fn content_row(grid: &SudokuGrid, y: usize) -> String { line(grid, '║', '║', '│', |x| to_char(grid.get_cell(x, y).unwrap()), ' ', '║', true) } impl Display for SudokuGrid { fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result { let size = self.size(); if size > 9 { return Err(Error::default()); } let top_row = top_row(self); let thin_separator_line = thin_separator_line(self); let thick_separator_line = thick_separator_line(self); let bottom_row = bottom_row(self); for y in 0..size { if y == 0 { f.write_str(top_row.as_str())?; } else if y % self.block_height == 0 { f.write_str(thick_separator_line.as_str())?; } else { f.write_str(thin_separator_line.as_str())?; } f.write_str(content_row(self, y).as_str())?; } f.write_str(bottom_row.as_str())?; Ok(()) } } fn to_string(cell: &Option<usize>) -> String { if let Some(number) = cell { number.to_string() } else { String::from("") } } pub(crate) fn index(column: usize, row: usize, size: usize) -> usize { row * size + column } fn parse_dimensions(code: &str) -> Result<(usize, usize), SudokuParseError> { let parts: Vec<&str> = code.split('x').collect(); if parts.len() != 2 { return Err(SudokuParseError::MalformedDimensions); } Ok((parts[0].parse()?, parts[1].parse()?)) } impl SudokuGrid { /// Creates a new, empty Sudoku grid where the blocks have the given /// dimensions. The total width and height of the grid will be equal to the /// product of `block_width` and `block_height`. /// /// # Arguments /// /// * `block_width`: The horizontal dimension of one sub-block of the grid. /// To ensure a square grid, this is also the number of blocks that compose /// the grid vertically. For an ordinary Sudoku grid, this is 3. Must be /// greater than 0. /// * `block_height`: The vertical dimension of one sub-block of the grid. /// To ensure a square grid, this is also the number of blocks that compose /// the grid horizontally. For an ordinary Sudoku grid, this is 3. Must be /// greater than 0. /// /// # Errors /// /// If `block_width` or `block_height` is invalid (zero). pub fn new(block_width: usize, block_height: usize) -> SudokuResult<SudokuGrid> { if block_width == 0 || block_height == 0 { return Err(SudokuError::InvalidDimensions); } let size = block_width * block_height; let cells = vec![None; size * size]; Ok(SudokuGrid { block_width, block_height, size, cells }) } /// Parses a code encoding a Sudoku grid. The code has to be of the format /// `<block_width>x<block_height>;<cells>` where `<cells>` is a /// comma-separated list of entries, which are either empty or a number. /// The entries are assigned left-to-right, top-to-bottom, where each row /// is completed before the next one is started. Whitespace in the entries /// is ignored to allow for more intuitive formatting. The number of /// entries must match the amount of cells in a grid with the given /// dimensions, i.e. it must be `(block_width · block_height)²`. /// /// As an example, the code `2x2;1, ,2, , ,3, ,4, , , ,3, ,1, ,2` will /// parse to the following grid: /// /// ```text /// ╔═══╤═══╦═══╤═══╗ /// ║ 1 │ ║ 2 │ ║ /// ╟───┼───╫───┼───╢ /// ║ │ 3 ║ │ 4 ║ /// ╠═══╪═══╬═══╪═══╣ /// ║ │ ║ 3 │ ║ /// ╟───┼───╫───┼───╢ /// ║ │ 1 ║ │ 2 ║ /// ╚═══╧═══╩═══╧═══╝ /// ``` /// /// # Errors /// /// Any specialization of `SudokuParseError` (see that documentation). pub fn parse(code: &str) -> SudokuParseResult<SudokuGrid> { let parts: Vec<&str> = code.split(';').collect(); if parts.len() != 2 { return Err(SudokuParseError::WrongNumberOfParts); } let (block_width, block_height) = parse_dimensions(parts[0])?; if let Ok(mut grid) = SudokuGrid::new(block_width, block_height) { let size = grid.size(); let numbers: Vec<&str> = parts[1].split(',').collect(); if numbers.len() != size * size { return Err(SudokuParseError::WrongNumberOfCells); } for (i, number_str) in numbers.iter().enumerate() { let number_str = number_str.trim(); if number_str.is_empty() { continue; } let number = number_str.parse::<usize>()?; if number == 0 || number > size { return Err(SudokuParseError::InvalidNumber); } grid.cells[i] = Some(number); } Ok(grid) } else { Err(SudokuParseError::InvalidDimensions) } } /// Converts the grid into a `String` in a way that is consistent with /// [SudokuGrid::parse](#method.parse). That is, a grid that is converted /// to a string and parsed again will not change, as is illustrated below. /// /// ``` /// use sudoku_variants::SudokuGrid; /// /// let mut grid = SudokuGrid::new(3, 2).unwrap(); /// /// // Just some arbitrary changes to create some content. /// grid.set_cell(1, 1, 4).unwrap(); /// grid.set_cell(1, 2, 5).unwrap(); /// /// let grid_str = grid.to_parseable_string(); /// let grid_parsed = SudokuGrid::parse(grid_str.as_str()).unwrap(); /// assert_eq!(grid, grid_parsed); /// ``` pub fn to_parseable_string(&self) -> String { let mut s = format!("{}x{};", self.block_width, self.block_height); let cells = self.cells.iter() .map(to_string) .collect::<Vec<String>>() .join(","); s.push_str(cells.as_str()); s } /// Gets the width (number of columns) of one sub-block of the grid. To /// ensure a square grid, this is also the number of blocks that compose /// the grid vertically. pub fn block_width(&self) -> usize { self.block_width } /// Gets the height (number of rows) of one sub-block of the grid. To /// ensure a square grid, this is also the number of blocks that compose /// the grid horizontally. pub fn block_height(&self) -> usize { self.block_height } /// Gets the total size of the grid on one axis (horizontally or /// vertically). Since a square grid is enforced at construction time, this /// is guaranteed to be valid for both axes. pub fn size(&self) -> usize { self.size } /// Gets the content of the cell at the specified position. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the desired cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the desired cell. Must be in the /// range `[0, size[`. /// /// # Errors /// /// If either `column` or `row` are not in the specified range. In that /// case, `SudokuError::OutOfBounds` is returned. pub fn get_cell(&self, column: usize, row: usize) -> SudokuResult<Option<usize>> { let size = self.size(); if column >= size || row >= size { Err(SudokuError::OutOfBounds) } else { let index = index(column, row, size); Ok(self.cells[index]) } } /// Indicates whether the cell at the specified position has the given /// number. This will return `false` if there is a different number in that /// cell or it is empty. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the checked cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the checked cell. Must be in the /// range `[0, size[`. /// * `number`: The number to check whether it is in the specified cell. If /// it is *not* in the range `[1, size]`, `false` will always be returned. /// /// # Errors /// /// If either `column` or `row` are not in the specified range. In that /// case, `SudokuError::OutOfBounds` is returned. pub fn has_number(&self, column: usize, row: usize, number: usize) -> SudokuResult<bool> { if let Some(content) = self.get_cell(column, row)? { Ok(number == content) } else { Ok(false) } } /// Sets the content of the cell at the specified position to the given /// number. If the cell was not empty, the old number will be overwritten. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the assigned cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the assigned cell. Must be in the /// range `[0, size[`. /// * `number`: The number to assign to the specified cell. Must be in the /// range `[1, size]`. /// /// # Errors /// /// * `SudokuError::OutOfBounds` If either `column` or `row` are not in the /// specified range. /// * `SudokuError::InvalidNumber` If `number` is not in the specified /// range. pub fn set_cell(&mut self, column: usize, row: usize, number: usize) -> SudokuResult<()> { let size = self.size(); if column >= size || row >= size { return Err(SudokuError::OutOfBounds); } if number == 0 || number > size { return Err(SudokuError::InvalidNumber); } let index = index(column, row, size); self.cells[index] = Some(number); Ok(()) } /// Clears the content of the cell at the specified position, that is, if /// contains a number, that number is removed. If the cell is already /// empty, it will be left that way. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the cleared cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the cleared cell. Must be in the /// range `[0, size[`. /// /// # Errors /// /// If either `column` or `row` are not in the specified range. In that /// case, `SudokuError::OutOfBounds` is returned. pub fn clear_cell(&mut self, column: usize, row: usize) -> SudokuResult<()> { let size = self.size(); if column >= size || row >= size { return Err(SudokuError::OutOfBounds); } let index = index(column, row, size); self.cells[index] = None; Ok(()) } fn verify_dimensions(&self, other: &SudokuGrid) -> SudokuResult<()> { if self.block_width != other.block_width || self.block_height != other.block_height { Err(SudokuError::InvalidDimensions) } else { Ok(()) } } /// Assigns the content of another grid to this one, i.e., changes the /// cells in this grid to the state in `other`. The other grid must have /// the same dimensions as this one. /// /// # Errors /// /// If the dimensions are not the same. In that case, /// `SudokuError::InvalidDimensions` is returned. pub fn assign(&mut self, other: &SudokuGrid) -> SudokuResult<()> { self.verify_dimensions(other)?; self.cells.copy_from_slice(&other.cells); Ok(()) } /// Counts the number of clues given by this grid. This is the number of /// non-empty cells. While on average Sudoku with less clues are harder, /// this is *not* a reliable measure of difficulty. pub fn count_clues(&self) -> usize { let size = self.size(); let mut clues = 0usize; for row in 0..size { for column in 0..size { if self.get_cell(column, row).unwrap().is_some() { clues += 1; } } } clues } /// Indicates whether this grid is full, i.e. every cell is filled with a /// number. In this case, [SudokuGrid::count_clues] returns the square of /// [SudokuGrid::size]. pub fn is_full(&self) -> bool { !self.cells.iter().any(|c| c == &None) } /// Indicates whether this grid is empty, i.e. no cell is filled with a /// number. In this case, [SudokuGrid::count_clues] returns 0. pub fn is_empty(&self) -> bool { self.cells.iter().all(|c| c == &None) } /// Indicates whether this grid configuration is a subset of another one. /// That is, all cells filled in this grid with some number must be filled /// in `other` with the same number. If this condition is met, `true` is /// returned, and `false` otherwise. /// /// # Errors /// /// If the dimensions of this and the `other` grid are not the same. In /// that case, `SudokuError::InvalidDimensions` is returned. pub fn is_subset(&self, other: &SudokuGrid) -> SudokuResult<bool> { self.verify_dimensions(other)?; Ok(self.cells.iter() .zip(other.cells.iter()) .all(|(self_cell, other_cell)| { match self_cell { Some(self_number) => match other_cell { Some(other_number) => self_number == other_number, None => false }, None => true } })) } /// Indicates whether this grid configuration is a superset of another one. /// That is, all cells filled in the `other `grid with some number must be /// filled in this one with the same number. If this condition is met, /// `true` is returned, and `false` otherwise. /// /// # Errors /// /// If the dimensions of this and the `other` grid are not the same. In /// that case, `SudokuError::InvalidDimensions` is returned. pub fn is_superset(&self, other: &SudokuGrid) -> SudokuResult<bool> { other.is_subset(self) } /// Gets a reference to the vector which holds the cells. They are in /// left-to-right, top-to-bottom order, where rows are together. pub fn cells(&self) -> &Vec<Option<usize>> { &self.cells } /// Gets a mutable reference to the vector which holds the cells. They are /// in left-to-right, top-to-bottom order, where rows are together. pub fn cells_mut(&mut self) -> &mut Vec<Option<usize>> { &mut self.cells } } /// A Sudoku represents a grid of numbers with an associated constraint. The /// numbers may or may not fulfill the constraint, but there is a method to /// check it. /// /// There is no guarantee that the Sudoku is uniquely solveable or even /// solveable at all, however there are ways to check that (see the [solver] /// module). #[derive(Clone)] pub struct Sudoku<C: Constraint + Clone> { grid: SudokuGrid, constraint: C } impl<C: Constraint + Clone> Sudoku<C> { /// Creates a new Sudoku with the provided constraint and an empty grid /// of the given dimensions. The total width and height of the grid will be /// equal to the product of `block_width` and `block_height`. /// /// # Arguments /// /// * `block_width`: The horizontal dimension of one sub-block of the grid. /// To ensure a square grid, this is also the number of blocks that compose /// the grid vertically. For an ordinary Sudoku grid, this is 3. Must be /// greater than 0. /// * `block_height`: The vertical dimension of one sub-block of the grid. /// To ensure a square grid, this is also the number of blocks that compose /// the grid horizontally. For an ordinary Sudoku grid, this is 3. Must be /// greater than 0. /// * `constraint`: The constraint which is checked by this Sudoku. Grid /// configurations which violate this constraint will be seen as invalid by /// [Sudoku::is_valid()]. /// /// # Errors /// /// If `block_width` or `block_height` is invalid (zero). pub fn new_empty(block_width: usize, block_height: usize, constraint: C) -> SudokuResult<Sudoku<C>> { Ok(Sudoku { grid: SudokuGrid::new(block_width, block_height)?, constraint }) } /// Creats a new Sudoku with the provided constraint and a given grid, /// which may already contain some numbers. Note that it is *not* checked /// whether the given grid fulfills the constraint - it is perfectly legal /// to create an invalid Sudoku here. /// /// # Arguments /// /// * `grid`: The initial [SudokuGrid] which contains the numbers with /// which the Sudoku is filled. /// * `constraint`: The constraint which is checked by this Sudoku. Grid /// configurations which violate this constraint will be seen as invalid by /// [Sudoku::is_valid]). pub fn new_with_grid(grid: SudokuGrid, constraint: C) -> Sudoku<C> { Sudoku { grid, constraint } } /// Parses the code into a [SudokuGrid] using [SudokuGrid::parse] and wraps /// the result in a Sudoku with the given constraint. Note that it is not /// required that the code matches the constraint. It is perfectly legal to /// parse an invalid Sudoku. /// /// # Arguments /// /// * `code`: The code that specifies the grid. See [SudokuGrid::parse] for /// a language specification. /// * `constraint`: The constraint which is checked by this Sudoku. Grid /// configurations which violate this constraint will be seen as invalid by /// [Sudoku::is_valid]. /// /// # Errors /// /// If the parsing fails. See [SudokuGrid::parse] for further information. pub fn parse(code: &str, constraint: C) -> SudokuParseResult<Sudoku<C>> { Ok(Sudoku::new_with_grid(SudokuGrid::parse(code)?, constraint)) } /// Gets a reference to the `SudokuGrid` of this Sudoku. pub fn grid(&self) -> &SudokuGrid { &self.grid } /// Gets a mutable reference to the `SudokuGrid` of this Sudoku. pub fn grid_mut(&mut self) -> &mut SudokuGrid { &mut self.grid } /// Gets a reference to the `Constraint` of this Sudoku. pub fn constraint(&self) -> &C { &self.constraint } /// Indicates whether the entire grid matches the constraint. pub fn is_valid(&self) -> bool { self.constraint.check(&self.grid) } /// Indicates whether the cell at the given location matches the /// constraint. That is, if the specified cell violates the constraint, /// `false` is returned, and `true` otherwise. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the checked cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the checked cell. Must be in the /// range `[0, size[`. pub fn is_valid_cell(&self, column: usize, row: usize) -> SudokuResult<bool> { let size = self.grid.size(); if column >= size || row >= size { Err(SudokuError::OutOfBounds) } else { Ok(self.constraint.check_cell(&self.grid, column, row)) } } /// Indicates whether the given number would be valid in the cell at the /// given location. That is, if the number violated the constraint, `false` /// is returned, and `true` otherwise. /// /// # Arguments /// /// * `column`: The column (x-coordinate) of the checked cell. Must be in /// the range `[0, size[`. /// * `row`: The row (y-coordinate) of the checked cell. Must be in the /// range `[0, size[`. /// * `number`: The number to check whether it is valid in the given cell. /// /// # Errors /// /// * `SudokuError::OutOfBounds` If either `column` or `row` are not in the /// specified range. /// * `SudokuError::InvalidNumber` If `number` is not in the specified /// range. pub fn is_valid_number(&self, column: usize, row: usize, number: usize) -> SudokuResult<bool> { let size = self.grid.size(); if column >= size || row >= size { Err(SudokuError::OutOfBounds) } else if number == 0 || number > size { Err(SudokuError::InvalidNumber) } else { Ok(self.constraint.check_number(&self.grid, column, row, number)) } } /// Indicates whether the given [SudokuGrid] is a valid solution to this /// puzzle. That is the case if all digits from this Sudoku can be found in /// the `solution`, it matches the constraint of this Sudoku, and it is /// full. /// /// # Errors /// /// If the dimensions of this Sudoku's grid and the `solution` grid are not /// the same. In that case, `SudokuError::InvalidDimensions` is returned. pub fn is_valid_solution(&self, solution: &SudokuGrid) -> SudokuResult<bool> { Ok(self.grid.is_subset(solution)? && self.constraint.check(solution) && solution.is_full()) } } #[cfg(test)] mod tests { use super::*; use crate::constraint::DefaultConstraint; #[test] fn parse_ok() { let grid_res = SudokuGrid::parse("2x2; 1,,,2, ,3,,4, ,2,,, 3,,,"); if let Ok(grid) = grid_res { assert_eq!(2, grid.block_width()); assert_eq!(2, grid.block_height()); assert_eq!(Some(1), grid.get_cell(0, 0).unwrap()); assert_eq!(None, grid.get_cell(1, 0).unwrap()); assert_eq!(None, grid.get_cell(2, 0).unwrap()); assert_eq!(Some(2), grid.get_cell(3, 0).unwrap()); assert_eq!(None, grid.get_cell(0, 1).unwrap()); assert_eq!(Some(3), grid.get_cell(1, 1).unwrap()); assert_eq!(None, grid.get_cell(2, 1).unwrap()); assert_eq!(Some(4), grid.get_cell(3, 1).unwrap()); assert_eq!(None, grid.get_cell(0, 2).unwrap()); assert_eq!(Some(2), grid.get_cell(1, 2).unwrap()); assert_eq!(None, grid.get_cell(2, 2).unwrap()); assert_eq!(None, grid.get_cell(3, 2).unwrap()); assert_eq!(Some(3), grid.get_cell(0, 3).unwrap()); assert_eq!(None, grid.get_cell(1, 3).unwrap()); assert_eq!(None, grid.get_cell(2, 3).unwrap()); assert_eq!(None, grid.get_cell(3, 3).unwrap()); } else { panic!("Parsing valid grid failed."); } } #[test] fn parse_malformed_dimensions() { assert_eq!(Err(SudokuParseError::MalformedDimensions), SudokuGrid::parse("2x2x2;,,,,,,,,,,,,,,,")); } #[test] fn parse_invalid_dimensions() { assert_eq!(Err(SudokuParseError::InvalidDimensions), SudokuGrid::parse("2x0;,")); } #[test] fn parse_wrong_number_of_parts() { assert_eq!(Err(SudokuParseError::WrongNumberOfParts), SudokuGrid::parse("2x2;,,,,,,,,,,,,,,,;whatever")); } #[test] fn parse_number_format_error() { assert_eq!(Err(SudokuParseError::NumberFormatError), SudokuGrid::parse("2x#;,")); } #[test] fn parse_invalid_number() { assert_eq!(Err(SudokuParseError::InvalidNumber), SudokuGrid::parse("2x2;,,,4,,,5,,,,,,,,,")); } #[test] fn parse_wrong_number_of_cells() { assert_eq!(Err(SudokuParseError::WrongNumberOfCells), SudokuGrid::parse("2x2;1,2,3,4,1,2,3,4,1,2,3,4,1,2,3")); assert_eq!(Err(SudokuParseError::WrongNumberOfCells), SudokuGrid::parse("2x2;1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4,1")); } #[test] fn to_parseable_string() { let mut grid = SudokuGrid::new(2, 2).unwrap(); assert_eq!("2x2;,,,,,,,,,,,,,,,", grid.to_parseable_string().as_str()); grid.set_cell(0, 0, 1).unwrap(); grid.set_cell(1, 1, 2).unwrap(); grid.set_cell(2, 2, 3).unwrap(); grid.set_cell(3, 3, 4).unwrap(); assert_eq!("2x2;1,,,,,2,,,,,3,,,,,4", grid.to_parseable_string().as_str()); let grid = SudokuGrid::new(4, 1).unwrap(); assert_eq!("4x1;,,,,,,,,,,,,,,,", grid.to_parseable_string().as_str()); } #[test] fn size() { let grid1x1 = SudokuGrid::new(1, 1).unwrap(); let grid3x2 = SudokuGrid::new(3, 2).unwrap(); let grid3x4 = SudokuGrid::new(3, 4).unwrap(); assert_eq!(1, grid1x1.size()); assert_eq!(6, grid3x2.size()); assert_eq!(12, grid3x4.size()); } #[test] fn count_clues_and_empty_and_full() { let empty = SudokuGrid::parse("2x2;,,,,,,,,,,,,,,,").unwrap(); let partial = SudokuGrid::parse("2x2;1,,3,2,4,,,,,,,,,,1,").unwrap(); let full = SudokuGrid::parse("2x2;2,3,4,1,1,4,2,3,4,1,3,2,3,2,1,4") .unwrap(); assert_eq!(0, empty.count_clues()); assert_eq!(5, partial.count_clues()); assert_eq!(16, full.count_clues()); assert!(empty.is_empty()); assert!(!partial.is_empty()); assert!(!full.is_empty()); assert!(!empty.is_full()); assert!(!partial.is_full()); assert!(full.is_full()); } fn assert_subset_relation(a: &SudokuGrid, b: &SudokuGrid, a_subset_b: bool, b_subset_a: bool) { assert!(a.is_subset(b).unwrap() == a_subset_b); assert!(a.is_superset(b).unwrap() == b_subset_a); assert!(b.is_subset(a).unwrap() == b_subset_a); assert!(b.is_superset(a).unwrap() == a_subset_b); } fn assert_true_subset(a: &SudokuGrid, b: &SudokuGrid) { assert_subset_relation(a, b, true, false) } fn assert_equal_set(a: &SudokuGrid, b: &SudokuGrid) { assert_subset_relation(a, b, true, true) } fn assert_unrelated_set(a: &SudokuGrid, b: &SudokuGrid) { assert_subset_relation(a, b, false, false) } #[test] fn empty_is_subset() { let empty = SudokuGrid::new(2, 2).unwrap(); let non_empty = SudokuGrid::parse("2x2;1,,,,,,,,,,,,,,,").unwrap(); let full = SudokuGrid::parse("2x2;1,2,3,4,3,4,1,2,2,3,1,4,4,1,3,2") .unwrap(); assert_equal_set(&empty, &empty); assert_true_subset(&empty, &non_empty); assert_true_subset(&empty, &full); } #[test] fn equal_grids_subsets() { let g = SudokuGrid::parse("2x2;1,,3,,2,,,,4,,4,3,,,,2").unwrap(); assert_equal_set(&g, &g); } #[test] fn true_subset() { let g1 = SudokuGrid::parse("2x2;1,,3,,2,,,,4,,4,3,,,,2").unwrap(); let g2 = SudokuGrid::parse("2x2;1,2,3,,2,,3,,4,,4,3,,,1,2").unwrap(); assert_true_subset(&g1, &g2); } #[test] fn unrelated_grids_not_subsets() { // g1 and g2 differ in the third digit (3 in g1, 4 in g2) let g1 = SudokuGrid::parse("2x2;1,,3,,2,,,,4,,4,3,,,,2").unwrap(); let g2 = SudokuGrid::parse("2x2;1,2,4,,2,,3,,4,,4,3,,,1,2").unwrap(); assert_unrelated_set(&g1, &g2); } fn solution_example_sudoku() -> Sudoku<DefaultConstraint> { Sudoku::parse("2x2;\ 2, , , ,\ , ,3, ,\ , , ,4,\ ,2, , ", DefaultConstraint).unwrap() } #[test] fn solution_not_full() { let sudoku = solution_example_sudoku(); let solution = SudokuGrid::parse("2x2;\ 2,3,4,1,\ 1,4,3, ,\ 3,1,2,4,\ 4,2,1,3").unwrap(); assert!(!sudoku.is_valid_solution(&solution).unwrap()); } #[test] fn solution_not_superset() { let sudoku = solution_example_sudoku(); let solution = SudokuGrid::parse("2x2;\ 2,3,4,1,\ 1,4,3,2,\ 3,2,1,4,\ 4,1,2,3").unwrap(); assert!(!sudoku.is_valid_solution(&solution).unwrap()); } #[test] fn solution_violates_constraint() { let sudoku = solution_example_sudoku(); let solution = SudokuGrid::parse("2x2;\ 2,3,4,1,\ 1,3,3,2,\ 3,1,2,4,\ 4,2,1,3").unwrap(); assert!(!sudoku.is_valid_solution(&solution).unwrap()); } #[test] fn solution_correct() { let sudoku = solution_example_sudoku(); let solution = SudokuGrid::parse("2x2;\ 2,3,4,1,\ 1,4,3,2,\ 3,1,2,4,\ 4,2,1,3").unwrap(); assert!(sudoku.is_valid_solution(&solution).unwrap()); } }