【Rust】哈希映射（三）

环境

• Time 2022-03-24
• Rust 1.59.0

示例

hasher

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

reserve

fn main() {
    let mut map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.reserve(4);
    println!("{:?}", map.capacity());
}

try_reserve

fn main() {
    let mut map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.try_reserve(4).unwrap();
    println!("{:?}", map.capacity());
}

shrink_to_fit

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

shrink_to

fn main() {
    let mut map = HashMap::from([("a", 1), ("b", 2), ("c", 3)]);
    map.shrink_to(4);
    println!("{:?}", map.capacity());
}

entry

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

get

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

get_key_value

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

contains_key

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

总结

了解了哈希映射中相关的一些方法。

附录