VecDeque. With the VecDeque in Rust, part of the std collections, we have a ring buffer. The front and back of the VecDeque can be added to or removed from with good performance.
Based on a Vector, the VecDeque helps us maintain the buffer's elements. To add elements, we use push_back or push_front. To remove elements, we use pop_back or pop_front.
Example. This program uses the Rust VecDeque in a variety of ways. It adds to the end and start with push_back and push_front, then loops over the elements.
Part 1 We create a VecDeque with the new() method. We call push_back 3 times and add integers to the buffer.
Part 2 We can use a for-loop to iterate over the elements stored within the VecDeque.
Part 6 For removing elements, we can use pop_back and pop_front. We can even rotate elements left and right.
use std::collections::*;
fn main() {
// Part 1: create VecDeque and add 3 elements to it with push_back.
let mut v = VecDeque::new();
v.push_back(100);
v.push_back(200);
v.push_back(300);
// Part 2: loop over VecDeque.
for element in v {
println!("Element: {element}");
}
// Part 3: create VecDeque with a starting capacity, and use push_front.
let mut x = VecDeque::with_capacity(10);
x.push_back("my");
x.push_back("friend");
x.push_back("!");
x.push_front("hello");
// Part 4: access front and back of VecDeque.
if let Some(front) = x.front() {
if let Some(back) = x.back() {
println!("front = {}; back = {}", front, back);
}
}
// Part 5: clone and convert into a Vec.
let result = x.clone().into_iter().collect::<Vec<&str>>();
println!("clone {:?}", result);
// Part 6: pop_back and rotate_left.
x.pop_back();
println!("pop_back {:?}", x);
x.rotate_left(1);
println!("rotate_left {:?}", x);
}Element: 100
Element: 200
Element: 300
front = hello; back = !
clone ["hello", "my", "friend", "!"]
pop_back ["hello", "my", "friend"]
rotate_left ["my", "friend", "hello"]
Summary. As it uses a Vector internally, the VecDeque could be replaced with a Vector. But by using the pre-built VecDeque helper methods, our programs are shorter and easier to maintain.
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