sudoku with simple backtracking

2024-11-28 12:02:18 +01:00 · 2024-11-28 12:02:18 +01:00 · 9a0a9afe37
commit 9a0a9afe37
5 changed files with 435 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@ -0,0 +1 @@
+/target
--- a/Cargo.lock
+++ b/Cargo.lock
@ -0,0 +1,147 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "getrandom"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "wasi",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.166"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2ccc108bbc0b1331bd061864e7cd823c0cab660bbe6970e66e2c0614decde36"
+
+[[package]]
+name = "ppv-lite86"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77957b295656769bb8ad2b6a6b09d897d94f05c41b069aede1fcdaa675eaea04"
+dependencies = [
+ "zerocopy",
+]
+
+[[package]]
+name = "proc-macro2"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37d3544b3f2748c54e147655edb5025752e2303145b5aefb3c3ea2c78b973bb0"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "sudoku"
+version = "0.1.0"
+dependencies = [
+ "rand",
+ "text_io",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.89"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44d46482f1c1c87acd84dea20c1bf5ebff4c757009ed6bf19cfd36fb10e92c4e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "text_io"
+version = "0.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d5f0c8eb2ad70c12a6a69508f499b3051c924f4b1cfeae85bfad96e6bc5bba46"
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "adb9e6ca4f869e1180728b7950e35922a7fc6397f7b641499e8f3ef06e50dc83"
+
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+
+[[package]]
+name = "zerocopy"
+version = "0.7.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b9b4fd18abc82b8136838da5d50bae7bdea537c574d8dc1a34ed098d6c166f0"
+dependencies = [
+ "byteorder",
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.7.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa4f8080344d4671fb4e831a13ad1e68092748387dfc4f55e356242fae12ce3e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
--- a/Cargo.toml
+++ b/Cargo.toml
@ -0,0 +1,10 @@
+[package]
+name = "sudoku"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+rand = "0.8.5"
+text_io = "0.1.12"
--- a/shell.nix
+++ b/shell.nix
@ -0,0 +1,18 @@
+{ pkgs ? import <nixpkgs> { overlays = [ (import (builtins.fetchTarball https://github.com/mozilla/nixpkgs-mozilla/archive/master.tar.gz)) ]; },}:
+with pkgs;
+
+mkShell {
+  nativeBuildInputs = with xorg; [
+    pkg-config
+  ] ++ [
+    cargo
+    rustc
+  ];
+  buildInputs = [
+    latest.rustChannels.stable.rust
+    xorg.libX11
+    xorg.libXi
+    xorg.libXtst
+    libevdev
+  ];
+}
--- a/src/main.rs
+++ b/src/main.rs
@ -0,0 +1,259 @@
+use std::fmt;
+use std::collections::HashSet;
+use rand::seq::SliceRandom;
+
+#[derive(Clone)]
+struct Cell {
+	value: Option<u8>,
+	possibilities: Vec<u8>
+}
+
+impl Cell {
+	fn set(&mut self, value: u8) {
+		self.value = if value > 0 && value < 10 {
+			Some(value)
+		} else {
+			None
+		};
+	}
+
+	fn reset_possibilities(&mut self) {
+		self.possibilities = (1..=9).collect();
+	}
+
+	fn remove_possibilities(&mut self, possibilities: &HashSet<u8>) {
+		self.possibilities.retain(|&x| !possibilities.contains(&x))
+	}
+}
+
+impl Default for Cell {
+	fn default() -> Self {
+		Self {
+			value: None,
+			possibilities: (1..=9).collect(),
+		}
+	}
+}
+
+impl fmt::Display for Cell {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if let Some(v) = self.value {
+            write!(f, "{}", v)
+        } else {
+            write!(f, " ")
+        }
+    }
+}
+
+struct Choice {
+	cell_selected: [usize; 2],
+	possibilities: Vec<u8>,
+	selected_value: u8,
+}
+
+struct Sudoku {
+	grid: [[Cell; 9]; 9],
+	rng: rand::rngs::ThreadRng,
+	history: Vec<Choice>,
+}
+
+impl Sudoku {
+	fn new(sudoku_set: [[u8; 9]; 9]) -> Self {
+		let mut sudoku_grid: [[Cell; 9]; 9] = [[(); 9]; 9].map(|_| [(); 9].map(|_| Cell::default()));
+
+	    for (row_index, row) in sudoku_set.iter().enumerate(){
+        	for (column_index, value) in row.iter().enumerate() {
+        		sudoku_grid[row_index][column_index].set(*value)
+        	}
+        }
+
+		Self {
+			grid: sudoku_grid,
+			rng: rand::thread_rng(),
+			history: vec![],
+		}
+	}
+
+	fn display(&self) {
+		println!("# sudoku grid : ");
+        for row in &self.grid {
+        	let mut line: String = "[".to_string();
+        	for cell in row {
+        		line += &format!("{}|",cell);
+        	}
+        	line.pop();
+        	println!("{}]",line);
+        }
+    }
+
+    fn update_possibilities(&mut self) {
+    	self.update_rows();
+    	self.update_columns();
+    	self.update_squares();
+    }
+
+    fn update_rows(&mut self) {
+    	for row_index in 0..9 {
+    		let mut used_values: HashSet<u8> = HashSet::new();
+    		
+    		for column_index in 0..9 {
+    			if let Some(value) = self.grid[row_index][column_index].value {
+    				used_values.insert(value);
+    			}
+    		}
+
+    		for column_index in 0..9 {
+    			self.grid[row_index][column_index].remove_possibilities(&used_values);
+    		}
+    	}
+    }
+
+    fn update_columns(&mut self) {
+        for column_index in 0..9 {
+        	let mut used_values: HashSet<u8> = HashSet::new();
+
+        	for row_index in 0..9 {
+        		if let Some(value) = self.grid[row_index][column_index].value {
+	   				used_values.insert(value);
+	   			}
+        	}
+
+        	for row_index in 0..9 {
+				self.grid[row_index][column_index].remove_possibilities(&used_values);
+        	}
+        }
+    }
+    
+    fn update_squares(&mut self) {
+        for square_row_index in 0..3 {
+        	for square_column_index in 0..3 {
+   	        	let mut used_values: HashSet<u8> = HashSet::new();
+
+   	        	for row_offset_index in 0..3 {
+   	        		for column_offset_index in 0..3 {
+						if let Some(value) = self.grid[square_row_index * 3 + row_offset_index][square_column_index * 3 + column_offset_index].value {
+			   				used_values.insert(value);
+			   			}
+   	        		}
+				}
+
+   	        	for row_offset_index in 0..3 {
+   	        		for column_offset_index in 0..3 {
+	   	        		self.grid[square_row_index * 3 + row_offset_index][square_column_index * 3 + column_offset_index].remove_possibilities(&used_values.clone());
+	   	        	}
+   	        	}
+   	        }
+        }
+    }
+
+    fn collapse(&mut self) -> bool {
+		let mut min_row_index: usize = 0;
+		let mut min_column_index: usize = 0;
+		let mut min_len: usize = 9;
+
+		let mut grid_has_empty_cell: bool = false;
+		
+    	for row_index in 0..9 {
+    		for column_index in 0..9 {
+    			if !self.grid[row_index][column_index].value.is_none() {
+    				continue;
+    			}
+    			grid_has_empty_cell = true;
+    			let possibilities_len = self.grid[row_index][column_index].possibilities.len();
+				if possibilities_len < min_len {
+					min_row_index = row_index;
+					min_column_index = column_index;
+					min_len = possibilities_len;
+				}
+    		}
+    	}
+
+    	if !grid_has_empty_cell {
+    		println!("x no empty cells");
+    		return false
+    	}
+    	
+    	if self.collapse_cell(min_row_index, min_column_index) {
+   	        return true
+   	    }
+
+		let mut fork: Option<Choice> = None;
+		
+        while let Some(choice) = self.history.pop() {
+        	println!("* backtracking");
+        	self.grid[choice.cell_selected[0]][choice.cell_selected[1]].value = None;
+        	if choice.possibilities.len() > 1 {
+        		fork = Some(choice);
+        		break;
+        	}
+        }
+
+        if let Some(choice) = fork {
+        	self.reset_possibilities();
+        	let mut choice_value = HashSet::new();
+        	choice_value.insert(choice.selected_value);
+			self.grid[choice.cell_selected[0]][choice.cell_selected[1]].remove_possibilities(&choice_value);
+        	return self.collapse_cell(choice.cell_selected[0], choice.cell_selected[1])
+        } else {
+        	println!("x backtracked to start");
+        	return false
+        }
+    }
+
+    fn reset_possibilities(&mut self) {
+    	for row in &mut self.grid {
+    		for cell in row {
+    			cell.reset_possibilities();
+    		}
+    	}
+    	
+        self.update_possibilities();
+    }
+
+    fn collapse_cell(&mut self, row_index: usize, column_index: usize) -> bool {
+    	if let Some(&selected_value) = self.grid[row_index][column_index].possibilities.choose(&mut self.rng) {
+	    	self.history.push(Choice {
+				cell_selected: [row_index, column_index],
+				possibilities: self.grid[row_index][column_index].possibilities.clone(),
+				selected_value,
+			});
+
+	  	    self.grid[row_index][column_index].set(selected_value);
+			println!("# collapsing [{}][{}] ({:?}) to {}", row_index, column_index, self.grid[row_index][column_index].possibilities, selected_value);
+			return true
+		} else {
+   	    	println!("x no possibilities for [{}][{}]", row_index, column_index);
+			return false
+		}
+    }
+}
+
+fn main() {
+    let sudoku_set: [[u8; 9]; 9] = [
+    	[6,0,0,0,0,2,1,0,0],
+    	[0,3,2,9,0,0,0,7,0],
+    	[0,0,0,0,0,8,0,0,0],
+    	[2,0,0,0,0,0,4,0,0],
+    	[7,0,3,0,0,0,9,1,0],
+    	[0,8,0,0,9,4,0,0,0],
+    	[0,0,4,0,0,0,6,0,0],
+    	[1,2,0,7,0,0,0,0,5],
+    	[0,0,0,0,0,0,0,9,4],
+    ];
+
+    let mut sudoku = Sudoku::new(sudoku_set);
+
+    sudoku.display();
+
+    println!("--------");
+
+    sudoku.update_possibilities();
+
+    while sudoku.collapse() {
+    	sudoku.update_possibilities();
+    }
+
+    println!("--------");
+
+    sudoku.display();
+}