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use crate::NodeKeyRef;
/// A priority queue which allows pushing (N, K)=(node, key) pairs to the collection,
/// and popping the foremost element having the lowest key.
pub trait PriorityQueue<N, K>
where
K: PartialOrd,
{
/// Item providing references to node & key pairs which are yielded by the iterator.
type NodeKey<'a>: NodeKeyRef<'a, N, K>
where
Self: 'a,
N: 'a,
K: 'a;
/// An iterator over the (node, key) pairs on the priority queue in an arbitrary order.
type Iter<'a>: Iterator<Item = Self::NodeKey<'a>>
where
Self: 'a,
N: 'a,
K: 'a;
/// Number of elements in the queue.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = DaryHeap::<_, _, 16>::default();
///
/// queue.push('a', 42);
/// queue.push('b', 7);
/// assert_eq!(2, queue.len());
///
/// _ = queue.pop();
/// assert_eq!(1, queue.len());
/// ```
fn len(&self) -> usize;
/// Capacity of the heap.
fn capacity(&self) -> usize;
/// Returns whether he queue is empty or not.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = QuaternaryHeap::default();
/// assert!(queue.is_empty());
///
/// queue.push("wisdom", 42);
/// assert!(!queue.is_empty());
/// ```
fn is_empty(&self) -> bool {
self.len() == 0
}
/// Returns, without popping, a reference to the foremost element of the queue;
/// returns None if the queue is empty.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert_eq!(None, queue.peek());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(Some(&(42, 1.0)), queue.peek());
/// ```
fn peek(&self) -> Option<Self::NodeKey<'_>>;
/// Clears the queue.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = QuaternaryHeap::default();
/// assert!(queue.is_empty());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert!(!queue.is_empty());
///
/// queue.clear();
/// assert!(queue.is_empty());
/// ```
fn clear(&mut self);
/// Removes and returns the (node, key) pair with the lowest key in the queue;
/// returns None if the queue is empty.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert_eq!(None, queue.pop());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(3, queue.len());
///
/// assert_eq!(Some((42, 1.0)), queue.pop());
/// assert_eq!(2, queue.len());
///
/// assert_eq!(Some((21, 5.0)), queue.pop());
/// assert_eq!(1, queue.len());
///
/// assert_eq!(Some((0, 12.0)), queue.pop());
/// assert!(queue.is_empty());
///
/// assert_eq!(None, queue.pop());
/// ```
fn pop(&mut self) -> Option<(N, K)>;
/// Removes and returns the node with the lowest key in the queue;
/// returns None if the queue is empty.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert_eq!(None, queue.pop_node());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(3, queue.len());
///
/// assert_eq!(Some(42), queue.pop_node());
/// assert_eq!(2, queue.len());
///
/// assert_eq!(Some(21), queue.pop_node());
/// assert_eq!(1, queue.len());
///
/// assert_eq!(Some(0), queue.pop_node());
/// assert!(queue.is_empty());
///
/// assert_eq!(None, queue.pop_node());
/// ```
fn pop_node(&mut self) -> Option<N>;
/// Removes and returns the key of the node with the lowest key in the queue;
/// returns None if the queue is empty.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert_eq!(None, queue.pop_key());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(3, queue.len());
///
/// assert_eq!(Some(1.0), queue.pop_key());
/// assert_eq!(2, queue.len());
///
/// assert_eq!(Some(5.0), queue.pop_key());
/// assert_eq!(1, queue.len());
///
/// assert_eq!(Some(12.0), queue.pop_key());
/// assert!(queue.is_empty());
///
/// assert_eq!(None, queue.pop_key());
/// ```
fn pop_key(&mut self) -> Option<K>;
/// Pushes the given (`node`, `key`) pair to the queue.
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert!(queue.is_empty());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(3, queue.len());
/// ```
fn push(&mut self, node: N, key: K);
/// Performs the push with given (`node`, `key`) followed by the pop operation.
///
/// Since the queue cannot be empty after the push, the return type is not optional.
///
/// The reason of merging the calls is that handling two instructions at once is
/// significantly more efficient for implementations taking benefit of this composition.
/// `DaryHeap` and its variants such the `BinaryHeap` are examples to this (see "benches/push_then_pop.rs").
///
/// # Examples
///
/// ```
/// use orx_priority_queue::*;
///
/// let mut queue = BinaryHeap::default();
/// assert!(queue.is_empty());
///
/// // returns the (node, key) back when the queue is empty
/// let popped = queue.push_then_pop(3, 33.3);
/// assert_eq!((3, 33.3), popped);
/// assert!(queue.is_empty());
///
/// queue.push(0, 12.0);
/// queue.push(42, 1.0);
/// queue.push(21, 5.0);
/// assert_eq!(3, queue.len()); // sorted-nodes: 42 (1.0) << 21 (5.0) << 0 (12.0)
///
/// let popped = queue.push_then_pop(100, 100.0);
/// assert_eq!((42, 1.0), popped);
/// assert_eq!(3, queue.len()); // sorted-nodes: 21 (5.0) << 0 (12.0) << 100 (100.0)
///
/// let popped = queue.push_then_pop(6, 6.0);
/// assert_eq!((21, 5.0), popped);
/// assert_eq!(3, queue.len()); // sorted-nodes: 6 (6.0) << 0 (12.0) << 100 (100.0)
///
/// let popped = queue.push_then_pop(13, 13.0);
/// assert_eq!((6, 6.0), popped);
/// assert_eq!(3, queue.len()); // sorted-nodes: 0 (12.0) << 13 (13.0) << 100 (100.0)
///
/// assert_eq!(Some((0, 12.0)), queue.pop());
/// assert_eq!(Some((13, 13.0)), queue.pop());
/// assert_eq!(Some((100, 100.0)), queue.pop());
/// assert!(queue.is_empty());
/// ```
fn push_then_pop(&mut self, node: N, key: K) -> (N, K);
/// Returns an iterator visiting all values on the heap in arbitrary order.
fn iter(&self) -> Self::Iter<'_>;
}