【Rust】哈希映射（一）

环境

• Time 2022-03-24
• Rust 1.59.0

示例

new

fn main() {
    let map: HashMap<&str, i32> = HashMap::new();
    println!("{:?}", map.capacity());
}

with_capacity

fn main() {
    let map: HashMap<&str, i32> = HashMap::with_capacity(4);
    println!("{:?}", map.capacity());
}

with_hasher

fn main() {
    let s = RandomState::new();
    let map: HashMap<&str, i32> = HashMap::with_hasher(s);
    println!("{:?}", map.capacity());
}

with_capacity_and_hasher

fn main() {
    let s = RandomState::new();
    let map: HashMap<&str, i32> = HashMap::with_capacity_and_hasher(4, s);
    println!("{:?}", map.capacity());
}

capacity

fn main() {
    let map: HashMap<&str, i32> = HashMap::with_capacity(4);
    println!("{:?}", map.capacity());
}

keys

fn main() {
    let map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.keys().for_each(|e| println!("{e:?}"));
}

into_keys

fn main() {
    let map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.into_keys().for_each(|e| println!("{e:?}"));
}

values

fn main() {
    let map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.values().for_each(|e| println!("{e:?}"));
}

values_mut

fn main() {
    let mut map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.values_mut().for_each(|e| println!("{e:?}"));
}

总结

了解了哈希映射中相关的一些方法。

附录