fn sector_addr(&self, sector_id: usize) -> (usize, usize) {
        let sector_addr = sector_id - 1;
        let min_y = (sector_addr / 3) * 5;
        let min_x = (sector_addr % 3) * 5;

        (min_x, min_y)
    }
// sectors numbered 1 to 9, 5x5 cells/sector, first horizontal then vertical
sectors numbered 1 to 9, 5x5 cells/sector, first horizontal then vertical
sectors numbered 1 to 9 5x5 cells / sector first horizontal then vertical
fn sector_addr(&self, sector_id: usize) -> (usize, usize) {
        let sector_addr = sector_id - 1;
        let min_y = (sector_addr / 3) * 5;
        let min_x = (sector_addr % 3) * 5;
        (min_x, min_y)
    }
fn sector_addr ( & self , sector_id : usize ) -> ( usize , usize ) { let sector_addr = sector_id - 1 ; let min_y = ( sector_addr / 3 ) * 5 ; let min_x = ( sector_addr % 3 ) * 5 ; ( min_x , min_y ) }
sectors numbered 1 to 9, 5x5 cells/sector, first horizontal then vertical
sectors numbered 1 to 9 5x5 cells / sector first horizontal then vertical
&self
sector_id
usize
&self
sector_id
usize