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HashSet in Rust Programming
Rust also provides us with a HashSet data structure that is mainly used when we want to make sure that no duplicate values are present in our data structure.
If we try to insert a new value into a HashSet that is already present in it, then the previous value gets overwritten by the new value that we inserted
Besides the key features, a HashSet is also used to do the following operations −
- union − Extract all the unique elements in both sets.
- difference −G ets all the elements that are present in the first set, but not in the second.
- intersection − Gets all the elements that are present in both sets.
- symmertric_difference − Gets all the elements that are in one set or the other, but not in both.
Example
Consider the example shown below −
use std::collections::HashSet;
fn main() {
let mut a: HashSet = vec![1i32, 2, 3].into_iter().collect();
let mut b: HashSet = vec![2i32, 3, 4].into_iter().collect();
assert!(a.insert(4));
assert!(a.contains(&4));
// `HashSet::insert()` returns false if value already present
assert!(b.insert(4), "Value 4 is already in set B!");
b.insert(5);
}In this example, we created a HashSet and then inserted the values in it. If we try to insert values that are already present, then the insert() function will return a false. Hence the above code will return an error.
Output
thread 'main' panicked at 'Value 4 is already in set B!', src/main.rs:11:5 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Example
Now let us try to make use of all the methods that are available on a HashSet. Consider the example shown below −
use std::collections::HashSet;
fn main() {
let mut a: HashSet = vec![1i32, 2, 3].into_iter().collect();
let mut b: HashSet = vec![2i32, 3, 4].into_iter().collect();
assert!(a.insert(4));
assert!(a.contains(&4));
b.insert(6);
println!("A: {:?}", a);
println!("B: {:?}", b);
println!("Union: {:?}", a.union(&b).collect::>());
println!("Difference: {:?}",
a.difference(&b).collect::>());
println!("Intersection: {:?}",
a.intersection(&b).collect::>());
println!("Symmetric Difference: {:?}",
a.symmetric_difference(&b).collect::>());
}Output
A: {1, 2, 3, 4}
B: {4, 6, 2, 3}
Union: [1, 2, 3, 4, 6]
Difference: [1]
Intersection: [2, 3, 4]
Symmetric Difference: [1, 6]
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