rust map

fn main() {
    use std::collections::HashMap;

    let mut m = HashMap::new();
    m.insert(1,"a");
    m.insert(2,"b");
    m.insert(2,"bb");//替换
    m.entry(2).or_insert("bbb");//没有则插入
    m.insert(3,"c");
    let key = 3;
    //修改值
    *m.entry(3).or_insert("c") = "cc";

    let key = 1;
    let value = m.get(&key);

    //遍历map
    for (key,value) in &m{
        println!("{}:{}",key,value);
    }

    //直接打印map
    println!("{:?}", m);
}

1:a
2:bb
3:cc
{1: "a", 2: "bb", 3: "cc"}