如何将一个HashSet的所有值插入另一个HashSet? [英] How can I insert all values of one HashSet into another HashSet?

问题描述

我有两个 HashSet< u16> s，我想实现 a = a b .如果可能的话，我想使用 HashSet :: union 而不是循环或其他调整.

I have two HashSet<u16>s and I would like to implement a = a U b. If possible, I'd like to use HashSet::union rather than loops or other tweaks.

我尝试了以下操作:

use std::collections::HashSet;
let mut a: HashSet<u16> = [1, 2, 3].iter().cloned().collect();
let b: HashSet<u16> = [7, 8, 9].iter().cloned().collect();  

// I can build a union object that contains &u16
let union: HashSet<&u16> = a.union(&b).collect();

// But I can't store the union into a
a = a.union(&b).collect();   //  -> compile error

// of course I can do
for x in &b {
    a.insert(*x);
}
// but I wonder if union could not be used to simply build a union

错误消息如下:

the trait bound 
`std::collections::HashSet<u16>: std::iter::FromIterator<&u16>`
is not satisfied

如何执行 a = A b ?

推荐答案

您不希望 union —如您所说，它将创建一个新的 HashSet .相反，您可以使用 Extend :: extend :

You don't want union — as you said, it will create a new HashSet. Instead you can use Extend::extend:

use std::collections::HashSet;

fn main() {
    let mut a: HashSet<u16> = [1, 2, 3].iter().copied().collect();
    let b: HashSet<u16> = [1, 3, 7, 8, 9].iter().copied().collect();

    a.extend(&b);

    println!("{:?}", a); // {8, 3, 2, 1, 7, 9}
}

(游乐场)

Extend :: extend 也是已为其他集合实现，例如 Vec . Vec 的结果将有所不同，因为 Vec 不会以与 Set 相同的方式兑现重复项.

Extend::extend is also implemented for other collections, e.g. Vec. The result for Vec will differ because Vec does not honor duplicates in the same way a Set does.

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