Initial sudoku solver with parser and formatter.

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "sudoku-solver"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "sudoku-solver"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/board.rs

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+use std::fmt::{self, Write};
+
+pub enum Square {
+    Value(u8),
+    Options(Vec<u8>),
+}
+
+impl Square {
+    pub fn from_char(c: char) -> Square {
+        match c {
+            '1' => Square::Value(1),
+            '2' => Square::Value(2),
+            '3' => Square::Value(3),
+            '4' => Square::Value(4),
+            '5' => Square::Value(5),
+            '6' => Square::Value(6),
+            '7' => Square::Value(7),
+            '8' => Square::Value(8),
+            '9' => Square::Value(9),
+            '.' => Square::Options(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]),
+            _ => panic!("Unexpected character in input: {}", c),
+        }
+    }
+
+    pub fn to_str(&self) -> String {
+        match self {
+            Square::Options(_) => " ".to_string(),
+            Square::Value(v) => v.to_string(),
+        }
+    }
+}
+
+pub struct Board {
+    squares: Vec<Square>,
+}
+
+impl Board {
+    pub fn from_string(str: &str) -> Board {
+        if str.len() != 81 {
+            panic!("Input string not length 81: got {}", str.len())
+        }
+        let mut squares = Vec::new();
+        for c in str.chars() {
+            squares.push(Square::from_char(c))
+        }
+        Board { squares }
+    }
+}
+
+impl fmt::Debug for Board {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("-------------\n")?;
+        for r in 0..9 {
+            f.write_char('|')?;
+            for c in 0..9 {
+                f.write_str(&self.squares[r * 9 + c].to_str())?;
+                if c == 2 || c == 5 || c == 8 {
+                    f.write_char('|')?;
+                }
+            }
+            f.write_char('\n')?;
+            if r == 2 || r == 5 || r == 8 {
+                f.write_str("-------------\n")?;
+            }
+        }
+        Ok(())
+    }
+}

src/main.rs

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+mod board;
+
+fn main() {
+    let nyt_hard = "3...184.9\
+                    8.47.....\
+                    .....61..\
+                    4....25.8\
+                    ..3.....4\
+                    ....4..2.\
+                    ...6.1...\
+                    17.2.....\
+                    5........";
+    let sudoku_board = board::Board::from_string(nyt_hard);
+    println!("{:#?}", sudoku_board);
+}