use std::collections::HashMap;
fn main() {
    let text = String::from("aa bb cc d aa c c");
    let mut m: HashMap<&str, i32> = HashMap::new();
    for w in text.split_whitespace() {
        let c = m.entry(w).or_insert(0);
        *c += 1;
    }

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