bitboard

bitboard.rs

struct Board {
    cells: [u8; 81],
    row_mask: [u16; 9],
    col_mask: [u16; 9],
    box_mask: [u16; 9],
}

impl Board {
    fn bit(&self, d: u8) -> u16 {
        1 << (d - 1)
    }

    fn get_box_mask_index(&self, row: usize, col: usize) -> usize {
        (row / 3) * 3 + (col / 3)
    }

    fn get_value_mask_index(&self, row: usize, col: usize) -> usize {
        (row * 9) + col
    }

    fn candidates_mask(&self, row: usize, col: usize) -> u16 {
        if(self.cells[self.get_value_mask_index(row, col)] != 0) {
            return 0;
        }

        let b = self.get_box_mask_index(row, col);
        self.row_mask[row] & self.col_mask[col] & self.box_mask[b]
    }

    fn print(&self) {
        for r in 0..9 {
            if r % 3 == 0 && r != 0 {
                println!("------+-------+------");
            }
            for c in 0..9 {
                if c % 3 == 0 && c != 0 {
                    print!("| ");
                }
                let v = self.cells[r * 9 + c];
                if v == 0 {
                    print!(". ");
                } else {
                    print!("{} ", v);
                }
            }
            println!();
        }
    }

    fn debug(&self) {
        println!("Cells:");
        for r in 0..9 {
            for c in 0..9 {
                let v = self.cells[r * 9 + c];
                print!("{:04b} ", v); 
            }
            println!();
        }

        println!("\nRow masks:");
        for r in 0..9 {
            println!("row {}: {:09b}", r, self.row_mask[r]);
        }

        println!("\nCol masks:");
        for c in 0..9 {
            println!("col {}: {:09b}", c, self.col_mask[c]);
        }

        println!("\nBox masks:");
        for b in 0..9 {
            println!("box {}: {:09b}", b, self.box_mask[b]);
        }
    }
}

fn main() {
    let mut board = Board {
        cells: [0; 81],
        row_mask: [0x1FF; 9],
        col_mask: [0x1FF; 9],
        box_mask: [0x1FF; 9],
    };

    let b = board.bit(2);
    let box_index = board.get_box_mask_index(0, 0);
    let value_index = board.get_value_mask_index(0, 0);

    board.cells[value_index] = 2;
    board.row_mask[0] &= !b;
    board.col_mask[0] &= !b;
    board.box_mask[box_index] &= !b;

    board.print();
    board.debug();
    print!("{:09b}", board.candidates_mask(0, 0));
    print!("{:09b}", board.candidates_mask(1, 3));
}