rust HashSet怎么判空

可以使用 `is_empty()` 方法来判空，该方法返回一个布尔值，如果 HashSet 为空则返回 true，否则返回 false。示例代码如下：

use std::collections::HashSet;

fn main() {
    let mut set = HashSet::new();

    if set.is_empty() {
        println!("set is empty");
    } else {
        println!("set is not empty");
    }

    set.insert(1);

    if set.is_empty() {
        println!("set is empty");
    } else {
        println!("set is not empty");
    }
}

输出结果为：

set is empty
set is not empty

相关问题

rust hashset

Rust 标准库中提供了 HashSet 类型来实现哈希集合的功能。HashSet 是一个无序的集合，它可以存储不重复的元素，并且能够快速地进行插入、删除和查找操作。

要使用 HashSet，首先需要在代码中引入该类型：

use std::collections::HashSet;

然后可以创建一个新的 HashSet，并向其中插入元素：

let mut hash_set = HashSet::new();

hash_set.insert(1);
hash_set.insert(2);
hash_set.insert(3);

可以使用 `contains` 方法来检查 HashSet 中是否包含某个元素：

assert!(hash_set.contains(&1));
assert!(!hash_set.contains(&4));

可以使用 `remove` 方法来删除 HashSet 中的元素：

hash_set.remove(&2);
assert!(!hash_set.contains(&2));

还可以使用 `len` 方法获取 HashSet 的大小：

assert_eq!(hash_set.len(), 2);

这只是 HashSet 的一些基本用法示例，你可以根据自己的需求进一步探索 Rust 的 HashSet 类型。

rust HashSet

The Rust HashSet is a collection type that represents a set of unique values. It is implemented using a hash table, which provides fast lookups and insertions. The HashSet is generic over the type of values it stores, allowing it to be used with any type that implements the Eq and Hash traits.

Creating a HashSet in Rust is straightforward:

use std::collections::HashSet;

let mut set = HashSet::new();

// Add values to the set
set.insert(1);
set.insert(2);
set.insert(3);

// Check if a value is in the set
assert!(set.contains(&2));

// Remove a value from the set
set.remove(&2);

// Iterate over the values in the set
for value in &set {
    println!("{}", value);
}

The HashSet provides several methods for working with sets, such as union, intersection, and difference. It also provides methods for checking if a set is a subset or superset of another set.

let set1: HashSet<i32> = [1, 2, 3].iter().cloned().collect();
let set2: HashSet<i32> = [3, 4, 5].iter().cloned().collect();

// Union
let union: HashSet<_> = set1.union(&set2).cloned().collect();
assert_eq!(union, [1, 2, 3, 4, 5].iter().cloned().collect());

// Intersection
let intersection: HashSet<_> = set1.intersection(&set2).cloned().collect();
assert_eq!(intersection, [3].iter().cloned().collect());

// Difference
let difference: HashSet<_> = set1.difference(&set2).cloned().collect();
assert_eq!(difference, [1, 2].iter().cloned().collect());

// Subset/superset
assert!(set1.is_subset(&union));
assert!(union.is_superset(&set1));

Overall, the HashSet is a useful collection type in Rust for working with sets of unique values. Its hash table implementation provides efficient lookups and insertions, and its generic nature allows it to be used with any type that implements the Eq and Hash traits.