[Rust] set binary operation demo

// Call HashSet from library
use std::collections::HashSet;

fn main() {
    // Get two sets from two arrays
    let a: HashSet<_> = [1, 2, 3].iter().cloned().collect();
    let b: HashSet<_> = [4, 2, 3, 4].iter().cloned().collect();

    // Get the union of the two sets
    let union: HashSet<_> = a.union(&b).cloned().collect();
    assert_eq!(union, [1, 2, 3, 4].iter().cloned().collect());

    // Get the intersection of the two sets
    let intersection: HashSet<_> = a.intersection(&b).cloned().collect();
    assert_eq!(intersection, [2, 3].iter().cloned().collect());

    // Get the difference of a from b
    let diff: HashSet<_> = a.difference(&b).cloned().collect();
    assert_eq!(diff, [1].iter().cloned().collect());
}