use std::collections::HashMap;

fn main() {
    let mut map: HashMap<String, usize> = HashMap::new();

    let words = [
        "foo", "bar", "baz", "foo", "baz", "meta", "bar", "meta", "qux",
    ];

    for word in words.iter() {
        map.get_mut(*word)
            .map(|count| *count += 1)
            .unwrap_or_else(|| {
                map.insert((*word).into(), 1);
            });
    }

    println!("{:?}", map);
}