use std::collections::HashMap;

fn set_if_needed_and_get(hmap: &mut HashMap<String, String>, st: String) -> &String {
    return hmap.entry(st.clone()).or_insert(st.clone());
}

fn main() {
    let meeting_one_email = ["email1", "email2", "email1"];

    let mut hmap: HashMap<String, String> = HashMap::new();
    let mut attendees: std::vec::Vec<&String> = std::vec::Vec::new();

    for m in meeting_one_email.iter() {
        {
            attendees.push(set_if_needed_and_get(&mut hmap, m.to_string()));
        }
    }
}

fn main() {
    let meeting_one_email = ["email1", "email2", "email1"];

    let mut hmap: HashMap<String, String> = HashMap::new();

    for m in meeting_one_email.iter() {
        set_if_needed_and_get(&mut hmap, m.to_string());
    }
    let attendees: Vec<&String> = hmap.keys().collect();
}