pub fn freeze_nonexisting_edges(&mut self) {
        for i in 0..self.atoms.len() {
            for j in 0..i {
                if *self.bonds.get(i, j) == 0 {
                    self.set_edge_impossible(i, j);
                    self.set_edge_impossible(j, i);
                }
            }
        }
    }
/// In some cases, it is known that certain edges can never exist.
/// Since a 4-subgraph is fully connected (as far as the molecules its based on allows it),
/// that is such a case.
/// Then we can mark these edges so that they can never be added again.
In some cases, it is known that certain edges can never exist.
Since a 4-subgraph is fully connected (as far as the molecules its based on allows it),
that is such a case.
Then we can mark these edges so that they can never be added again.
In some cases it is known that certain edges can never exist . Since a 4 - subgraph is fully connected ( as far as the molecules its based on allows it ) that is such a case . Then we can mark these edges so that they can never be added again .
pub fn freeze_nonexisting_edges(&mut self) {
        for i in 0..self.atoms.len() {
            for j in 0..i {
                if *self.bonds.get(i, j) == 0 {
                    self.set_edge_impossible(i, j);
                    self.set_edge_impossible(j, i);
                }
            }
        }
    }
pub fn freeze_nonexisting_edges ( & mut self ) { for i in 0 .. self . atoms . len ( ) { for j in 0 .. i { if * self . bonds . get ( i , j ) == 0 { self . set_edge_impossible ( i , j ) ; self . set_edge_impossible ( j , i ) ; } } } }
In some cases, it is known that certain edges can never exist.
In some cases it is known that certain edges can never exist .
&mut self