HashSet in Rust

Membership and set algebra, with no duplicate values by construction.

use std::collections::HashSet;

fn main() {
    let a: HashSet<i32> = [1, 2, 3, 4].into_iter().collect();
    let b: HashSet<i32> = [3, 4, 5].into_iter().collect();

    let mut both: Vec<&i32> = a.intersection(&b).collect();
    both.sort();
    println!("{:?}", both);

    let mut only_a: Vec<&i32> = a.difference(&b).collect();
    only_a.sort();
    println!("{:?}", only_a);

    let mut seen = HashSet::new();
    println!("{} {}", seen.insert("fig"), seen.insert("fig"));
}

How it works

1. insert returns false when the value was already present.
2. intersection and difference yield iterators, not sets.
3. collect builds a set straight from an iterator.

Keywords and builtins used here

• HashSet
• Vec
• fn
• i32
• let
• main
• mut
• use

The run, in numbers

Lines

17

Characters to type

441

Tokens

172

Three-star pace

90 tpm

At the three-star pace of 90 tokens a minute, this run takes about 115 seconds.

Type this snippet

Step 6 of 8 in Collections, step 35 of 39 in Language basics.

← Previous Next →