algorithms_edu/data_structures/
queue.rs

1pub trait Queue<T> {
2    fn with_capacity(capacity: usize) -> Self;
3    fn len(&self) -> usize;
4    fn is_empty(&self) -> bool {
5        self.len() == 0
6    }
7    fn push_back(&mut self, val: T);
8    fn pop_front(&mut self) -> Option<T>;
9}
10
11/// A custom implementation of a circular queue which is
12/// extremely quick and lightweight.
13/// However, the downside is you need to know an upper bound on the number of elements
14/// that will be inside the queue at any given time for this queue to work.
15pub struct FixedCapacityQueue<T: Clone> {
16    ar: Box<[Option<T>]>,
17    front: usize,
18    back: usize,
19    capacity: usize,
20}
21
22impl<T: Clone> FixedCapacityQueue<T> {
23    /// Initialize a queue where a maximum of `max_sz` elements can be
24    /// in the queue at any given time
25    pub fn with_capacity(capacity: usize) -> Self {
26        Self {
27            front: 0,
28            back: 0,
29            capacity,
30            ar: vec![None; capacity].into_boxed_slice(),
31        }
32    }
33
34    pub fn peek(&self) -> Option<&T> {
35        self.ar.get(self.front).and_then(|x| x.as_ref())
36    }
37}
38
39impl<T: Clone> Queue<T> for FixedCapacityQueue<T> {
40    fn len(&self) -> usize {
41        self.back - self.front
42    }
43    fn with_capacity(capacity: usize) -> Self {
44        Self::with_capacity(capacity)
45    }
46    fn push_back(&mut self, val: T) {
47        assert!(self.back < self.capacity, "Queue too small!");
48        self.ar[self.back] = Some(val);
49        self.back += 1;
50    }
51    fn pop_front(&mut self) -> Option<T> {
52        if self.is_empty() {
53            None
54        } else {
55            let res = self.ar[self.front].take();
56            self.front += 1;
57            res
58        }
59    }
60}
61
62impl<T: Clone> Queue<T> for std::collections::VecDeque<T> {
63    fn len(&self) -> usize {
64        self.len()
65    }
66    fn with_capacity(capacity: usize) -> Self {
67        Self::with_capacity(capacity)
68    }
69    fn push_back(&mut self, val: T) {
70        self.push_back(val);
71    }
72    fn pop_front(&mut self) -> Option<T> {
73        self.pop_front()
74    }
75}
algorithms_edu/data_structures/queue.rs

algorithms_edu/data_structures/
queue.rs
