You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
94 lines
2.0 KiB
Rust
94 lines
2.0 KiB
Rust
#![warn(rust_2018_idioms)]
|
|
#![allow(elided_lifetimes_in_paths)]
|
|
|
|
pub struct Queue<T> {
|
|
older: Vec<T>,
|
|
younger: Vec<T>
|
|
}
|
|
|
|
impl<T> Queue<T> {
|
|
pub fn new() -> Self {
|
|
Queue { older: Vec::new(), younger: Vec::new() }
|
|
}
|
|
|
|
pub fn push(&mut self, t: T) {
|
|
self.younger.push(t);
|
|
}
|
|
|
|
pub fn is_empty(&self) -> bool {
|
|
self.older.is_empty() && self.younger.is_empty()
|
|
}
|
|
|
|
pub fn pop(&mut self) -> Option<T> {
|
|
if self.older.is_empty() {
|
|
use std::mem::swap;
|
|
|
|
if self.younger.is_empty() {
|
|
return None;
|
|
}
|
|
|
|
// Bring the elements in younger over to older, and put them in
|
|
// the promised order.
|
|
swap(&mut self.older, &mut self.younger);
|
|
self.older.reverse();
|
|
}
|
|
|
|
// Now older is guaranteed to have something. Vec's pop method
|
|
// already returns an Option, so we're set.
|
|
self.older.pop()
|
|
}
|
|
|
|
pub fn split(self) -> (Vec<T>, Vec<T>) {
|
|
(self.older, self.younger)
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test() {
|
|
let mut q = Queue::new();
|
|
|
|
q.push('*');
|
|
assert_eq!(q.pop(), Some('*'));
|
|
assert_eq!(q.pop(), None);
|
|
|
|
q.push('0');
|
|
q.push('1');
|
|
assert_eq!(q.pop(), Some('0'));
|
|
|
|
q.push('∞');
|
|
assert_eq!(q.pop(), Some('1'));
|
|
assert_eq!(q.pop(), Some('∞'));
|
|
assert_eq!(q.pop(), None);
|
|
|
|
assert!(q.is_empty());
|
|
q.push('☉');
|
|
assert!(!q.is_empty());
|
|
q.pop();
|
|
assert!(q.is_empty());
|
|
|
|
let mut q = Queue::new();
|
|
|
|
q.push('P');
|
|
q.push('D');
|
|
assert_eq!(q.pop(), Some('P'));
|
|
q.push('X');
|
|
|
|
assert_eq!(q.split(), (vec!['D'], vec!['X']));
|
|
}
|
|
|
|
#[test]
|
|
fn test_generic() {
|
|
let mut q = Queue::<char>::new();
|
|
&mut q;
|
|
drop(q);
|
|
|
|
let mut q = Queue::new();
|
|
let mut r = Queue::new();
|
|
|
|
q.push("CAD"); // apparently a Queue<&'static str>
|
|
r.push(0.74); // apparently a Queue<f64>
|
|
|
|
q.push("BTC"); // Bitcoins per USD, 2019-6
|
|
r.push(13764.0); // Rust fails to detect irrational exuberance
|
|
}
|