Code shared from the Rust Playground

playground.rs

use std::collections::HashMap;
use std::vec::Vec;

fn main() -> ()
{
    let mut map : HashMap<String, String> = HashMap::new();
    map.insert("Bob".into(), "Marley".into());
    map.insert("Jack".into(), "Ryan".into());
    map.insert("Bill".into(), "Tilden".into());
    
    let mut keys : Vec<&str> = Vec::new(); 
    {
        let ks = map.keys();
        for key in ks
        {
            keys.push(key);
        }
    }
    
    let mut iter = keys.iter();
    loop
    {
        match iter.next() {
            Some(key) => {
                let key : String = (*key).into();
                map.remove(&key);
            }
            None => break
        }
    }
    
    println!("len {}", map.len());
}