Remove duplicates. In Rust we find a dedup function on Vectors. And this can be used to eliminate duplicates from a Vector—but only a sorted Vector.
Usage notes. When using dedup(), we must either have kept the vector in sorted order, or we need to sort it before calling dedup. Otherwise dedup and dedup_by_key will not work.
First example. Consider this string vector: it has 3 animal names, and they are not sorted. We must first sort the data collection before calling dedup.
Step 1 We call sort() with no argument to sort by value (alphabetically). The 2 birds are now at the start of the vector.
Step 2 Here we invoke dedup on the sorted list. We see that one of the 2 birds was removed, but the fish remains in the vector.
Tip Try removing the sort() call, and you will see that dedup does not work correctly without it.
fn main() {
let mut animals = vec!["bird", "fish", "bird"];
println!("{:?}", animals);
// Step 1: sort the vector.
animals.sort();
println!("{:?}", animals);
// Step 2: call dedup to remove duplicates in a sorted vector.
animals.dedup();
println!("{:?}", animals);
}["bird", "fish", "bird"]
["bird", "bird", "fish"]
["bird", "fish"]
Key example. In this example, we use the dedup_by_key function, along with sort_by_key. These 2 methods transform elements into keys before acting upon the values.
Info We pass a closure to the sort_by_key and dedup_by_key functions. It is easier to pass the closure directly as an argument.
Detail To treat "cat" in the same way as the "CAT," we call to_uppercase() to act upon all elements as though they are uppercase.
fn main() {
let mut animals = vec!["cat", "bird", "CAT"];
// First sort he vector with keys.// ... Then remove duplicates with keys.
animals.sort_by_key(|a| a.to_uppercase());
animals.dedup_by_key(|a| a.to_uppercase());
println!("{:?}", animals);
}["bird", "cat"]
A summary. In Rust, using dedup() and dedup_by_key() is often a 2-step process. We must first sort the vector before invoking these functions—just adjacent elements are removed.
Dot Net Perls is a collection of pages with code examples, which are updated to stay current. Programming is an art, and it can be learned from examples.
Donate to this site to help offset the costs of running the server. Sites like this will cease to exist if there is no financial support for them.
Sam Allen is passionate about computer languages, and he maintains 100% of the material available on this website. He hopes it makes the world a nicer place.