sorting causes move

main.rs

fn report_adjacency_list(g: HashMap<u32, Vec<u32>>){
    // need to sort 
    let sorted_keys = g.keys().sorted();
    
    println!("{}\t# number of vertices", g.len());
    
    let mut last_line = 1 + sorted_keys.len();

    for (i, k) in sorted_keys.enumerate() {
        let val = g.get(k).unwrap();
        
        println!("{}\t# starting value for vertex {}", last_line, i + 1);
        last_line = last_line + val.len();
    }

    // Good lord this is ugly. TODO: figure out how I can get sorted keys without 
    // using an iterator that consumes the collection, thus moving the pointer
    let sorted_keys_2 = g.keys().sorted();
    
    for k in sorted_keys_2 {
        let val = g.get(k).unwrap();
        for z in val{
            println!("{0} 1\t# Vertex {1} is adjacent to vertex {0}", z, k);
        }
    }
}