Cargo.toml

@@ -8,4 +8,6 @@ edition = "2018"
 
 [dependencies]
 csv = "1.1.3"
-argparse = "0.2.2"
+argparse = "0.2.2"
+rand = "0.7"
+rand_chacha = "0.2.2"

src/bin/generator.rs

@@ -0,0 +1,107 @@
+use rand_chacha::ChaCha8Rng;
+use rand::prelude::*;
+use sudoku_solver::grid::{Grid, CellValue};
+use std::error::Error;
+use std::io::Write;
+
+fn main() {
+
+    let mut debug = false;
+    // Starting default seed will just be based on time
+    let mut seed = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).expect("Time went backwards").as_secs();
+
+    let mut max_hints = 81;
+    let mut max_attempts = 100;
+    let mut filename : Option<String> = None;
+
+    { // this block limits scope of borrows by ap.refer() method
+        let mut ap = argparse::ArgumentParser::new();
+        ap.set_description("Generate Sudoku puzzles");
+        ap.refer(&mut debug)
+            .add_option(&["--debug"], argparse::StoreTrue, "Run in debug mode");
+
+        ap.refer(&mut seed)
+            .add_option(&["--seed"], argparse::Store, "Provide seed for puzzle generation");
+
+        ap.refer(&mut max_hints)
+            .add_option(&["--hints"], argparse::Store, "Only return a puzzle with less than or equal to this number of hints");
+
+        ap.refer(&mut max_attempts)
+            .add_option(&["--attempts"], argparse::Store, "Number of attempts that will be tried to generate such a puzzle; default is 100");
+
+        ap.refer(&mut filename)
+            .add_argument("filename", argparse::StoreOption, "Optional filename to store puzzle in as a CSV");
+
+        ap.parse_args_or_exit();
+    }
+
+    if debug {
+        unsafe {
+            sudoku_solver::grid::DEBUG = true;
+            sudoku_solver::solver::DEBUG = true;
+            sudoku_solver::generator::DEBUG = true;
+        }
+    }
+
+    if debug {
+        println!("Using seed {}", seed);
+    }
+    let mut rng = ChaCha8Rng::seed_from_u64(seed);
+
+    let mut num_attempts = 0;
+
+    let grid = loop {
+        if num_attempts >= max_attempts{
+            println!("Unable to find a puzzle with only {} hints in {} attempts", max_hints, max_attempts);
+            return;
+        }
+
+        let (grid, num_hints) = sudoku_solver::generator::generate_grid(&mut rng);
+        num_attempts = num_attempts + 1;
+
+        if num_hints <= max_hints {
+            println!("{}", grid);
+            println!("Puzzle has {} hints", num_hints);
+            if num_attempts > 1 {
+                println!("It took {} attempts to find this puzzle.", num_attempts);
+            }
+            break grid;
+        }
+    };
+
+    match filename {
+        Some(filename) => {
+            save_grid(&grid, &filename).unwrap();
+            println!("Grid saved to {}", filename);
+        },
+        None => {}
+    }
+
+}
+
+fn save_grid(grid: &Grid, filename: &str) -> Result<(), Box<dyn Error>>{
+    // Not using the csv crate for writing because it's being difficult and won't accept raw integers
+    let mut file = std::fs::File::create(filename)?;
+
+    for x in 0..9 {
+        for y in 0..9 {
+            let cell = grid.get(x, y).unwrap();
+            let value = &*cell.value.borrow();
+            let digit =
+            match value {
+                CellValue::Fixed(digit) => {*digit}
+                CellValue::Unknown(_) => {0}
+            };
+
+            let mut text = digit.to_string();
+            if y < 8 {
+                text.push(',');
+            }
+            file.write(text.as_bytes())?;
+
+        }
+        file.write(b"\n")?;
+    }
+
+    Ok(())
+}

src/generator.rs

@@ -0,0 +1,328 @@
+use crate::grid::{Cell, Grid, CellValue, Line};
+use crate::solver::{solve_grid_no_guess, SolveStatus, find_smallest_cell};
+use std::rc::Rc;
+use rand::prelude::*;
+use rand_chacha::ChaCha8Rng;
+
+pub static mut DEBUG : bool = false;
+
+// Extension of SolveStatus
+pub enum GenerateStatus {
+    UniqueSolution,
+    Unfinished,
+    NoSolution,
+    NotUniqueSolution
+}
+
+impl GenerateStatus {
+    fn increment(self, new_status : GenerateStatus) -> GenerateStatus {
+        match self {
+            GenerateStatus::UniqueSolution => {
+                match new_status {
+                    GenerateStatus::UniqueSolution => GenerateStatus::NotUniqueSolution, // We now have two completes, so the solutions are not unique
+                    GenerateStatus::NoSolution => GenerateStatus::UniqueSolution, // We already have a complete, so no issue with another guess being invalid
+                    GenerateStatus::Unfinished => {panic!("Should not have encountered an UNFINISHED status")},
+                    GenerateStatus::NotUniqueSolution => GenerateStatus::NotUniqueSolution // That solver found multiple solutions so no need to keep checking
+                }
+            },
+            GenerateStatus::Unfinished => {
+                match new_status {
+                    GenerateStatus::UniqueSolution => GenerateStatus::UniqueSolution,
+                    GenerateStatus::NoSolution => GenerateStatus::Unfinished,
+                    GenerateStatus::Unfinished => {panic!("Should not have encountered an UNFINISHED status")},
+                    GenerateStatus::NotUniqueSolution => GenerateStatus::NotUniqueSolution // That solver found multiple solutions so no need to keep checking
+                }
+            },
+            GenerateStatus::NotUniqueSolution => GenerateStatus::NotUniqueSolution,
+            GenerateStatus::NoSolution => GenerateStatus::NoSolution // This guess didn't pan out
+        }
+
+    }
+}
+
+impl SolveStatus {
+    fn map_to_generate_status(self) -> GenerateStatus {
+        match self {
+            SolveStatus::Complete => {GenerateStatus::UniqueSolution }
+            SolveStatus::Unfinished => {GenerateStatus::Unfinished }
+            SolveStatus::Invalid => {GenerateStatus::NoSolution }
+        }
+    }
+}
+
+impl Grid {
+    fn get_random_empty_cell(&self, rng : &mut ChaCha8Rng) -> Result<Rc<Cell>, &str> {
+        // Idea - put all empty cells into a vector and choose one at random
+        // If vector is empty we return an error
+
+        let mut empty_cells = Vec::new();
+        for x in 0..9 {
+            for y in 0..9 {
+                let cell = self.get(x, y).unwrap();
+                let add_cell = {
+                    let cell_value = &*cell.value.borrow();
+                    match cell_value { // May cause issues with borrow rules
+                        CellValue::Fixed(_) => {false}
+                        CellValue::Unknown(_) => {
+                            true
+                        }
+                    }
+                };
+                if add_cell {
+                    empty_cells.push(cell);
+                }
+            }
+        }
+
+        match empty_cells.iter().choose(rng) {
+            Some(cell) => Ok(Rc::clone(cell)),
+            None => Err("Unable to find an empty cell")
+        }
+    }
+}
+
+impl Cell {
+    fn delete_value(&self){
+        unsafe {
+            if DEBUG {
+                println!("Cell {}, {} had its value deleted.", self.x, self.y);
+            }
+        }
+
+        self.set_value_exact(CellValue::Unknown(vec![])); // placeholder
+
+        // This will reset all the possibilities for this cell and the ones that might have been limited by this cell
+        self.section.upgrade().unwrap().borrow().recalculate_and_set_possibilities();
+        self.row.upgrade().unwrap().borrow().recalculate_and_set_possibilities();
+        self.column.upgrade().unwrap().borrow().recalculate_and_set_possibilities();
+
+    }
+
+    /**
+        As part of delete_value, we need to manually recalculate possibilities for not just the cell whose value we deleted,
+        but also the other empty cells in the same row, column, and section.
+    */
+    fn calculate_possibilities(&self) -> Vec<u8> {
+        // Need to calculate possibilities for this cell
+        let mut possibilities = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
+        fn eliminate_possibilities(possibilities: &mut Vec<u8>, line: &Line, cell: &Cell){
+            for (_index, other) in line.vec.iter().enumerate(){
+                if other.x != cell.x || other.y != cell.y {
+                    let value = &*other.value.borrow();
+                    match value {
+                        CellValue::Fixed(digit) => {
+                            let location = possibilities.binary_search(digit);
+                            match location {
+                                Ok(location) => {
+                                    possibilities.remove(location);
+                                }
+                                Err(_) => {}
+                            }
+                        }
+                        CellValue::Unknown(_) => {}
+                    }
+                }
+            }
+        }
+
+        eliminate_possibilities(&mut possibilities, &self.section.upgrade().unwrap().borrow(), self);
+        eliminate_possibilities(&mut possibilities, &self.row.upgrade().unwrap().borrow(), self);
+        eliminate_possibilities(&mut possibilities, &self.column.upgrade().unwrap().borrow(), self);
+
+        return possibilities;
+    }
+}
+
+impl Line {
+    fn recalculate_and_set_possibilities(&self) {
+        for (_index, cell) in self.vec.iter().enumerate() {
+            let cell = &**cell;
+            let new_possibilities = {
+                let cell_value = &*cell.value.borrow();
+                match cell_value {
+                    CellValue::Fixed(_) => { continue; }
+                    CellValue::Unknown(_) => {
+                        cell.calculate_possibilities()
+                    }
+                }
+            };
+
+            cell.set_value_exact(CellValue::Unknown(new_possibilities));
+        }
+    }
+}
+
+pub fn generate_grid(rng: &mut ChaCha8Rng) -> (Grid, i32) {
+
+    let mut num_hints;
+    let mut grid : Grid = loop {
+        // First step; randomly assign 8 different digits to different empty cells and see if there's a possible solution
+        // We have to ensure that 8 of the digits appear at least once, otherwise the solution can't be unique because you could interchange the two missing digits throughout the puzzle
+        // We do this in a loop so that if we are really unlucky and our guesses stop there from being any solution, we can easily re-run it
+        let mut grid = Grid::new();
+        num_hints = 0;
+
+        let digit_excluded = rng.gen_range(1, 10);
+
+        for digit in 1..10 {
+            if digit != digit_excluded {
+                let cell = grid.get_random_empty_cell(rng);
+                cell.unwrap().set(digit);
+                num_hints = num_hints + 1;
+            }
+        }
+
+        let status = solve_grid(&mut grid);
+        match status {
+            GenerateStatus::UniqueSolution => { // very surprising result, given that the smallest puzzles found have 14 guesses
+                eprintln!("Wow! A puzzle with only 8 guesses have been found");
+                return (grid, num_hints);
+            }
+            GenerateStatus::Unfinished => {panic!("solve_grid should never return UNFINISHED")}
+            GenerateStatus::NoSolution => {continue;}
+            GenerateStatus::NotUniqueSolution => {break grid;}
+        };
+    };
+
+    // Alright, we now have a grid that we can start adding more guesses onto until we find a unique solution
+    grid =
+    'outer: loop {
+        num_hints = num_hints + 1;
+        let cell = grid.get_random_empty_cell(rng).unwrap(); // We unwrap because if somehow we're filled each cell without finding a solution, that's reason for a panic
+        let cell = &*cell;
+        let mut cell_possibilities = cell.get_value_possibilities().expect("An empty cell has no possibilities");
+
+        // Let's scramble the order
+        cell_possibilities.shuffle(rng);
+
+        for (_index, digit) in cell_possibilities.iter().enumerate() {
+
+            let grid_clone = grid.clone();
+            let cell = &*grid_clone.get(cell.x, cell.y).unwrap();
+
+            cell.set(*digit);
+
+            let status = solve_grid(&grid_clone);
+            match status {
+                GenerateStatus::UniqueSolution => { // We're done!
+                    break 'outer grid_clone;
+                }
+                GenerateStatus::Unfinished => {
+                    panic!("solve_grid should never return UNFINISHED")
+                }
+                GenerateStatus::NoSolution => { // Try another guess
+                    continue;
+                }
+                GenerateStatus::NotUniqueSolution => { // We need more guesses
+                    grid = grid_clone;
+                    continue 'outer;
+                }
+            }
+
+        };
+
+        // If we reach this point in the loop, then none of the possibilities for cell provided any solution
+        // Which means something serious happened before in the solving process - reason for panic
+        eprint!("No valid hints were found for puzzle\n{} at cell ({}, {})", grid, cell.x, cell.y);
+        panic!("Unable to continue as puzzle is invalid");
+
+
+    };
+
+    // At this point we have a valid puzzle, but from experience it has way too many guesses, and many of them
+    // are likely not needed. Let's now try removing a bunch.
+    let mut non_empty_cells = Vec::new();
+    for x in 0..9 {
+        for y in 0..9 {
+            let cell = grid.get(x, y).unwrap();
+            let value = &*cell.value.borrow();
+            match value {
+                CellValue::Fixed(_) => {non_empty_cells.push(Rc::clone(&cell))}
+                CellValue::Unknown(_) => {}
+            }
+        }
+    }
+    // Need to randomly reorder non_empty_cells
+    non_empty_cells.shuffle(rng);
+
+    for (_index, cell) in non_empty_cells.iter().enumerate() {
+        let grid_clone = grid.clone();
+        let cell_clone = grid_clone.get(cell.x, cell.y).unwrap();
+        let cell_clone = &*cell_clone;
+
+        cell_clone.delete_value();
+
+        let status = solve_grid(&mut grid);
+        match status {
+            GenerateStatus::UniqueSolution => { // great; that cell value was not needed
+                num_hints = num_hints - 1;
+                grid = grid_clone;
+
+            }
+            GenerateStatus::Unfinished => {panic!("solve_grid should never return UNFINISHED")}
+            GenerateStatus::NoSolution => {panic!("Removing constraints should not have set the # of solutions to zero")}
+            GenerateStatus::NotUniqueSolution => {continue;}
+        };
+    }
+
+    return (grid, num_hints);
+
+}
+
+fn solve_grid(grid: &Grid) -> GenerateStatus{
+    // Code is kind of messy so here it goes - solve_grid first tries to solve without any guesses
+    // If that's not enough and a guess is required, then solve_grid_guess is called
+    // solve_grid_guess runs through all the possibilities for the smallest cell, trying to solve them
+    // through calling this function.
+    // solve_grid_no_guess tries to solve without any guesses.
+
+    let mut grid = grid.clone(); // We're generating a result and don't want to make changes to our input
+
+    let mut status = solve_grid_no_guess(&mut grid).map_to_generate_status();
+    status = match status {
+        GenerateStatus::Unfinished => {
+            solve_grid_guess(&mut grid)
+        },
+        _ => {status}
+    };
+
+    match status {
+        GenerateStatus::Unfinished => panic!("solve_grid_guess should never return UNFINISHED"),
+        _ => return status
+    }
+}
+
+fn solve_grid_guess(grid: &Grid) -> GenerateStatus{
+    let smallest_cell = find_smallest_cell(grid);
+    let smallest_cell = match smallest_cell {
+        Some(cell) => cell,
+        None => return GenerateStatus::NoSolution
+    };
+
+    let possibilities = smallest_cell.get_value_possibilities().unwrap();
+
+    let mut current_status = GenerateStatus::Unfinished;
+
+    for (_index, &digit) in possibilities.iter().enumerate() {
+        let mut grid_copy = grid.clone();
+        grid_copy.get(smallest_cell.x, smallest_cell.y).unwrap().set(digit);
+        let status = solve_grid(&mut grid_copy);
+        current_status = current_status.increment(status);
+
+        match current_status {
+            GenerateStatus::NotUniqueSolution => return GenerateStatus::NotUniqueSolution, // We have our answer; return it
+            GenerateStatus::UniqueSolution => {continue}, // Still looking to see if solution is unique
+            GenerateStatus::NoSolution => {panic!("current_status should not be NO_SOLUTION at this point")},
+            GenerateStatus::Unfinished => {continue} // Still looking for a solution
+        }
+    }
+
+    // We've tried all the possibilities for this guess
+    match current_status {
+        GenerateStatus::NotUniqueSolution => return current_status,
+        GenerateStatus::Unfinished => return GenerateStatus::NoSolution, // nothing panned out; last guess is a bust
+        GenerateStatus::UniqueSolution => return current_status, // Hey! Looks good!
+        GenerateStatus::NoSolution => {panic!("current_status should not be NO_SOLUTION at this point")}
+    }
+
+}

src/grid.rs

@@ -6,8 +6,8 @@ pub static mut DEBUG: bool = false;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub enum CellValue {
-    FIXED(u8),
-    UNKNOWN(Vec<u8>)
+    Fixed(u8),
+    Unknown(Vec<u8>)
 }
 
 pub struct Cell {
@@ -27,7 +27,7 @@ impl Cell {
             }
         }
 
-        self.value.replace(CellValue::FIXED(digit));
+        self.value.replace(CellValue::Fixed(digit));
 
         // We fully expect our row, column, and section to still be here even though the Rust compiler won't guarantee it
         // Panic-ing if they're not present is perfectly reasonable
@@ -53,11 +53,11 @@ impl Cell {
 
     pub fn set_value(&self, value: CellValue){
         match value {
-            CellValue::FIXED(digit) => {
+            CellValue::Fixed(digit) => {
                 self.set(digit);
                 return;
             },
-            CellValue::UNKNOWN(_) => {
+            CellValue::Unknown(_) => {
                 self.set_value_exact(value);
             } // continue on
         }
@@ -77,8 +77,8 @@ impl Cell {
     pub fn get_value_possibilities(&self) -> Option<Vec<u8>> {
         let value = &*self.value.borrow();
         match value {
-            CellValue::FIXED(_) => None,
-            CellValue::UNKNOWN(x) => Some(x.clone())
+            CellValue::Fixed(_) => None,
+            CellValue::Unknown(x) => Some(x.clone())
         }
     }
 
@@ -109,7 +109,7 @@ impl Cell {
                 let value = &*cell.value.borrow();
 
                 match value {
-                    CellValue::UNKNOWN(possibilities) => {
+                    CellValue::Unknown(possibilities) => {
                         let mut new_possibilities = possibilities.clone();
 
                         match new_possibilities.binary_search(&digit) {
@@ -117,7 +117,7 @@ impl Cell {
                             _ => {}
                         };
 
-                        Some(CellValue::UNKNOWN(new_possibilities))
+                        Some(CellValue::Unknown(new_possibilities))
                         /*
                         if new_possibilities.len() == 1 {
                             let remaining_digit = new_possibilities.first().unwrap().clone();
@@ -128,7 +128,7 @@ impl Cell {
                             Some(CellValue::UNKNOWN(new_possibilities))
                         }*/
                     },
-                    CellValue::FIXED(_) => {None}
+                    CellValue::Fixed(_) => {None}
                 }
             };
 
@@ -152,9 +152,9 @@ pub struct Line {
 
 #[derive(Debug)]
 pub enum LineType {
-    ROW,
-    COLUMN,
-    SECTION
+    Row,
+    Column,
+    Section
 }
 
 impl Line {
@@ -199,9 +199,9 @@ impl Grid {
         let mut sections: Vec<MultiMut<Line>> = Vec::new();
 
         for i in 0..9 {
-            rows.push(Rc::new(RefCell::new(Line::new(i, LineType::ROW))));
-            columns.push(Rc::new(RefCell::new(Line::new(i, LineType::COLUMN))));
-            sections.push(Rc::new(RefCell::new(Line::new(i, LineType::SECTION))));
+            rows.push(Rc::new(RefCell::new(Line::new(i, LineType::Row))));
+            columns.push(Rc::new(RefCell::new(Line::new(i, LineType::Column))));
+            sections.push(Rc::new(RefCell::new(Line::new(i, LineType::Section))));
         }
 
         for row_index in 0..9 {
@@ -229,7 +229,7 @@ impl Grid {
                 let cell = Cell {
                     x: row_index,
                     y: column_index,
-                    value: RefCell::new(CellValue::UNKNOWN(vec![1, 2, 3, 4, 5, 6, 7, 8, 9])),
+                    value: RefCell::new(CellValue::Unknown(vec![1, 2, 3, 4, 5, 6, 7, 8, 9])),
                     row: row_weak,
                     column: column_weak,
                     section: section_weak
@@ -325,12 +325,12 @@ impl std::fmt::Display for Grid {
 
 
                 match value {
-                    CellValue::FIXED(x) => {
+                    CellValue::Fixed(x) => {
                         row1.push_str("   ");
                         row2.push(' '); row2.push_str(&x.to_string()); row2.push(' ');
                         row3.push_str("   ");
                     },
-                    CellValue::UNKNOWN(x) => {
+                    CellValue::Unknown(x) => {
                         Grid::process_unknown(&x, 1, &mut row1);
                         Grid::process_unknown(&x, 2, &mut row1);
                         Grid::process_unknown(&x, 3, &mut row1);

src/lib.rs

@@ -1,3 +1,3 @@
 pub mod grid;
-
-pub mod solver;
+pub mod solver;
+pub mod generator;

src/solver.rs

@@ -80,14 +80,14 @@ fn bisect_possibility_groups(line: &Line, cells_of_interest: Vec<usize>){
             let faux_possibilities = {
                 let value = &*cell.value.borrow();
                 match value {
-                    CellValue::UNKNOWN(possibilities) => {
+                    CellValue::Unknown(possibilities) => {
                         let mut set = HashSet::new();
                         for (_index, digit) in possibilities.iter().enumerate() {
                             set.insert(digit.clone());
                         }
                         set
                     },
-                    CellValue::FIXED(_) => { continue }
+                    CellValue::Fixed(_) => { continue }
                 }
             };
 
@@ -164,8 +164,8 @@ fn bisect_possibility_groups(line: &Line, cells_of_interest: Vec<usize>){
                 let mut possibilities = {
                     let value = &*real_cell.value.borrow();
                     match value {
-                        CellValue::UNKNOWN(possibilities) => possibilities.clone(),
-                        CellValue::FIXED(_) => {panic!("Faux_cell shouldn't have linked to fixed cell")}
+                        CellValue::Unknown(possibilities) => possibilities.clone(),
+                        CellValue::Fixed(_) => {panic!("Faux_cell shouldn't have linked to fixed cell")}
                     }
                 };
                 let starting_possibility_size = possibilities.len();
@@ -187,9 +187,9 @@ fn bisect_possibility_groups(line: &Line, cells_of_interest: Vec<usize>){
                 if possibilities.len() < starting_possibility_size { // We have a change to make
                     let new_value = {
                         if possibilities.len() == 1 {
-                            CellValue::FIXED(possibilities.pop().unwrap())
+                            CellValue::Fixed(possibilities.pop().unwrap())
                         } else {
-                            CellValue::UNKNOWN(possibilities)
+                            CellValue::Unknown(possibilities)
                         }
                     };
 
@@ -229,7 +229,7 @@ fn search_single_possibility(line: &Line){
         match cell.get_value_possibilities(){
             Some(x) => {
                 if x.len() == 1 {
-                    let new_value = CellValue::FIXED(x.first().unwrap().clone());
+                    let new_value = CellValue::Fixed(x.first().unwrap().clone());
                     cell.set_value(new_value);
                 }
             },
@@ -239,15 +239,15 @@ fn search_single_possibility(line: &Line){
 }
 
 enum PossibilityLines {
-    UNIQUE(usize),
-    INVALID,
-    NONE
+    Unique(usize),
+    Invalid,
+    None
 }
 
 impl PossibilityLines {
     fn is_invalid(&self) -> bool {
         match &self {
-            PossibilityLines::INVALID => true,
+            PossibilityLines::Invalid => true,
             _ => false
         }
     }
@@ -265,15 +265,15 @@ fn search_useful_constraint(grid: &Grid, line: &Line){
     }
 
     let (check_row, check_column, check_section) = match line.line_type {
-        LineType::ROW => {(false, false, true)},
-        LineType::COLUMN => {(false, false, true)},
-        LineType::SECTION => {(true, true, false)},
+        LineType::Row => {(false, false, true)},
+        LineType::Column => {(false, false, true)},
+        LineType::Section => {(true, true, false)},
     };
 
     for possibility in 0..9 {
-        let mut rows = match check_row {true => PossibilityLines::NONE, false => PossibilityLines::INVALID};
-        let mut columns = match check_column {true => PossibilityLines::NONE, false => PossibilityLines::INVALID};
-        let mut sections = match check_section {true => PossibilityLines::NONE, false => PossibilityLines::INVALID};
+        let mut rows = match check_row {true => PossibilityLines::None, false => PossibilityLines::Invalid };
+        let mut columns = match check_column {true => PossibilityLines::None, false => PossibilityLines::Invalid };
+        let mut sections = match check_section {true => PossibilityLines::None, false => PossibilityLines::Invalid };
 
         for cell_id in 0..9 {
             let cell_ref = line.get(cell_id).unwrap();
@@ -282,7 +282,7 @@ fn search_useful_constraint(grid: &Grid, line: &Line){
             let value = &*cell_ref.value.borrow();
 
             match value {
-                CellValue::FIXED(x) => { // We can deduce this possibility won't occur elsewhere in our row, so leave for-loop
+                CellValue::Fixed(x) => { // We can deduce this possibility won't occur elsewhere in our row, so leave for-loop
                     if possibility.eq(x) {
                         rows = process_possibility_line(rows, &cell_ref.row);
                         columns = process_possibility_line(columns, &cell_ref.column);
@@ -290,7 +290,7 @@ fn search_useful_constraint(grid: &Grid, line: &Line){
                         break;
                     }
                 }
-                CellValue::UNKNOWN(digits) => {
+                CellValue::Unknown(digits) => {
                     if digits.contains(&possibility) {
                         rows = process_possibility_line(rows, &cell_ref.row);
                         columns = process_possibility_line(columns, &cell_ref.column);
@@ -306,19 +306,19 @@ fn search_useful_constraint(grid: &Grid, line: &Line){
 
         // Check each line and see if we can determine anything
         match rows {
-            PossibilityLines::UNIQUE(index) => {
+            PossibilityLines::Unique(index) => {
                 remove_possibilities_line(grid.rows.get(index).unwrap(), possibility, &line.line_type, line.index);
             },
             _ => {}
         }
         match columns {
-            PossibilityLines::UNIQUE(index) => {
+            PossibilityLines::Unique(index) => {
                 remove_possibilities_line(grid.columns.get(index).unwrap(), possibility, &line.line_type, line.index);
             },
             _ => {}
         }
         match sections {
-            PossibilityLines::UNIQUE(index) => {
+            PossibilityLines::Unique(index) => {
                 remove_possibilities_line(grid.sections.get(index).unwrap(), possibility, &line.line_type, line.index);
             },
             _ => {}
@@ -335,11 +335,11 @@ fn remove_possibilities_line(line: &Rc<RefCell<Line>>, digit_to_remove: u8, init
         let new_value = {
             let value = &*cell.value.borrow();
             match value {
-                CellValue::UNKNOWN(possibilities) => {
+                CellValue::Unknown(possibilities) => {
                     let parent_line = match initial_line_type {
-                        LineType::ROW => &cell.row,
-                        LineType::COLUMN => &cell.column,
-                        LineType::SECTION => &cell.section
+                        LineType::Row => &cell.row,
+                        LineType::Column => &cell.column,
+                        LineType::Section => &cell.section
                     };
                     let parent_line = &*parent_line.upgrade().unwrap();
                     let parent_line = &*parent_line.borrow();
@@ -359,9 +359,9 @@ fn remove_possibilities_line(line: &Rc<RefCell<Line>>, digit_to_remove: u8, init
 
                     let new_value;
                     if new_possibilities.len() == 1 {
-                        new_value = CellValue::FIXED(new_possibilities.first().unwrap().clone());
+                        new_value = CellValue::Fixed(new_possibilities.first().unwrap().clone());
                     } else {
-                        new_value = CellValue::UNKNOWN(new_possibilities);
+                        new_value = CellValue::Unknown(new_possibilities);
                     }
 
                     new_value
@@ -381,13 +381,13 @@ fn process_possibility_line(possibility_line: PossibilityLines, line: &Weak<RefC
     let line = &*(&*line).borrow();
 
     match possibility_line {
-        PossibilityLines::NONE => {PossibilityLines::UNIQUE(line.index)},
-        PossibilityLines::INVALID => {possibility_line},
-        PossibilityLines::UNIQUE(x) => {
+        PossibilityLines::None => {PossibilityLines::Unique(line.index)},
+        PossibilityLines::Invalid => {possibility_line},
+        PossibilityLines::Unique(x) => {
             if line.index.eq(&x) {
                 possibility_line
             } else {
-                PossibilityLines::INVALID
+                PossibilityLines::Invalid
             }
         }
     }
@@ -426,7 +426,7 @@ fn solve_line(grid: &Grid, line: &Line){
 
 }
 
-fn find_smallest_cell(grid: &Grid) -> Option<Rc<Cell>>{
+pub fn find_smallest_cell(grid: &Grid) -> Option<Rc<Cell>>{
     // Find a cell of smallest size (in terms of possibilities) and make a guess
     // Can assume that no cells of only possibility 1 exist
 
@@ -440,7 +440,7 @@ fn find_smallest_cell(grid: &Grid) -> Option<Rc<Cell>>{
             let cell_value = &*cell.value.borrow();
 
             match cell_value {
-                CellValue::UNKNOWN(possibilities) => {
+                CellValue::Unknown(possibilities) => {
                     if (possibilities.len() < smallest_size) && (possibilities.len() > 0){
                         smallest_size = possibilities.len();
                         smallest_cell = Some(cell_rc);
@@ -461,9 +461,9 @@ fn find_smallest_cell(grid: &Grid) -> Option<Rc<Cell>>{
 
 
 pub enum SolveStatus {
-    COMPLETE,
-    UNFINISHED,
-    INVALID
+    Complete,
+    Unfinished,
+    Invalid
 }
 
 pub fn solve_grid(grid: &mut Grid) -> SolveStatus{
@@ -475,14 +475,14 @@ pub fn solve_grid(grid: &mut Grid) -> SolveStatus{
 
     let mut status = solve_grid_no_guess(grid);
     status = match status {
-        SolveStatus::UNFINISHED => {
+        SolveStatus::Unfinished => {
             solve_grid_guess(grid)
         },
         _ => {status}
     };
 
     match status {
-        SolveStatus::UNFINISHED => panic!("solve_grid_guess should never return UNFINISHED"),
+        SolveStatus::Unfinished => panic!("solve_grid_guess should never return UNFINISHED"),
         _ => return status
     }
 }
@@ -517,7 +517,7 @@ pub fn solve_grid_no_guess(grid: &mut Grid) -> SolveStatus{
         }
 
         if !ran_something{ // No lines have changed since we last analyzed them
-            return SolveStatus::UNFINISHED;
+            return SolveStatus::Unfinished;
         }
 
         // Check if complete or invalid
@@ -529,20 +529,20 @@ pub fn solve_grid_no_guess(grid: &mut Grid) -> SolveStatus{
                 let value = &**(&cell.value.borrow());
 
                 match value {
-                    CellValue::UNKNOWN(possibilities) => {
+                    CellValue::Unknown(possibilities) => {
                         appears_complete = false;
                         if possibilities.len() == 0 {
-                            return SolveStatus::INVALID;
+                            return SolveStatus::Invalid;
 
                         }
                     },
-                    CellValue::FIXED(_) => {}
+                    CellValue::Fixed(_) => {}
                 }
             }
         }
 
         if appears_complete {
-            return SolveStatus::COMPLETE;
+            return SolveStatus::Complete;
         }
     }
 
@@ -552,7 +552,7 @@ fn solve_grid_guess(grid: &mut Grid) -> SolveStatus{
     let smallest_cell = find_smallest_cell(grid);
     let smallest_cell = match smallest_cell {
         Some(cell) => cell,
-        None => return SolveStatus::INVALID
+        None => return SolveStatus::Invalid
     };
 
     let possibilities = smallest_cell.get_value_possibilities().unwrap();
@@ -562,20 +562,20 @@ fn solve_grid_guess(grid: &mut Grid) -> SolveStatus{
         let status = solve_grid(&mut grid_copy);
 
         match status {
-            SolveStatus::COMPLETE => {
+            SolveStatus::Complete => {
                 grid.clone_from(&grid_copy);
-                return SolveStatus::COMPLETE;
+                return SolveStatus::Complete;
             },
-            SolveStatus::UNFINISHED => {
+            SolveStatus::Unfinished => {
                 panic!("solve_grid should never return UNFINISHED")
             },
-            SolveStatus::INVALID => {
+            SolveStatus::Invalid => {
                 continue;
             }
         }
     }
 
-    return SolveStatus::INVALID;
+    return SolveStatus::Invalid;
 
 }
 
@@ -592,14 +592,14 @@ mod tests {
             grid.get(0, i).unwrap().set(i as u8 +1);
         }
 
-        assert_eq!(CellValue::UNKNOWN(vec![9]), grid.get(0, 8).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![9]), grid.get(0, 8).unwrap().get_value_copy());
 
         let line = grid.rows.first().unwrap();
         let line = &*(**line).borrow();
 
         search_single_possibility(line);
 
-        assert_eq!(CellValue::FIXED(9), grid.get(0, 8).unwrap().get_value_copy());
+        assert_eq!(CellValue::Fixed(9), grid.get(0, 8).unwrap().get_value_copy());
     }
 
     #[test]
@@ -614,14 +614,14 @@ mod tests {
         grid.get(1, 7).unwrap().set(2);
         grid.get(1, 8).unwrap().set(3);
 
-        assert_eq!(CellValue::UNKNOWN(vec![1, 2, 3, 7, 8, 9]), grid.get(0, 0).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![1, 2, 3, 7, 8, 9]), grid.get(0, 0).unwrap().get_value_copy());
 
         let line = grid.rows.first().unwrap();
         let line = &*(**line).borrow();
 
         identify_and_process_possibility_groups(line);
 
-        assert_eq!(CellValue::UNKNOWN(vec![1, 2, 3]), grid.get(0, 0).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![1, 2, 3]), grid.get(0, 0).unwrap().get_value_copy());
     }
 
     #[test]
@@ -638,14 +638,14 @@ mod tests {
 
 
 
-        assert_eq!(CellValue::UNKNOWN(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]), grid.get(2, 0).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]), grid.get(2, 0).unwrap().get_value_copy());
 
         let line = grid.rows.first().unwrap();
         let line = &*(**line).borrow();
 
         search_useful_constraint(&grid, line);
 
-        assert_eq!(CellValue::UNKNOWN(vec![4, 5, 6, 7, 8, 9]), grid.get(2, 0).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![4, 5, 6, 7, 8, 9]), grid.get(2, 0).unwrap().get_value_copy());
     }
 
 
@@ -661,15 +661,15 @@ mod tests {
         grid.get(6, 1).unwrap().set(8);
         grid.get(8, 2).unwrap().set(7);
 
-        grid.get(0, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 3, 4, 7, 9]));
-        grid.get(1, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 3, 4, 5, 9]));
-        grid.get(2, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 2]));
-        grid.get(4, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 3, 4, 7]));
-        grid.get(7, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 2, 3, 9]));
-        grid.get(8, 1).unwrap().set_value(CellValue::UNKNOWN(vec![1, 2, 3, 5, 9]));
+        grid.get(0, 1).unwrap().set_value(CellValue::Unknown(vec![1, 3, 4, 7, 9]));
+        grid.get(1, 1).unwrap().set_value(CellValue::Unknown(vec![1, 3, 4, 5, 9]));
+        grid.get(2, 1).unwrap().set_value(CellValue::Unknown(vec![1, 2]));
+        grid.get(4, 1).unwrap().set_value(CellValue::Unknown(vec![1, 3, 4, 7]));
+        grid.get(7, 1).unwrap().set_value(CellValue::Unknown(vec![1, 2, 3, 9]));
+        grid.get(8, 1).unwrap().set_value(CellValue::Unknown(vec![1, 2, 3, 5, 9]));
 
         // 5 is wrongly removed here
-        grid.get(1, 0).unwrap().set_value(CellValue::UNKNOWN(vec![1, 3, 4, 5, 9]));
+        grid.get(1, 0).unwrap().set_value(CellValue::Unknown(vec![1, 3, 4, 5, 9]));
 
         println!("{}", grid);
 
@@ -678,7 +678,7 @@ mod tests {
 
         search_useful_constraint(&grid, line);
 
-        assert_eq!(CellValue::UNKNOWN(vec![1, 3, 4, 5, 9]), grid.get(1, 0).unwrap().get_value_copy());
+        assert_eq!(CellValue::Unknown(vec![1, 3, 4, 5, 9]), grid.get(1, 0).unwrap().get_value_copy());
 
     }