1//! A priority queue implemented with a binary heap.
2//!
3//! Insertion and popping the largest element have *O*(log(*n*)) time complexity.
4//! Checking the largest element is *O*(1). Converting a vector to a binary heap
5//! can be done in-place, and has *O*(*n*) complexity. A binary heap can also be
6//! converted to a sorted vector in-place, allowing it to be used for an *O*(*n* * log(*n*))
7//! in-place heapsort.
8//!
9//! # Examples
10//!
11//! This is a larger example that implements [Dijkstra's algorithm][dijkstra]
12//! to solve the [shortest path problem][sssp] on a [directed graph][dir_graph].
13//! It shows how to use [`BinaryHeap`] with custom types.
14//!
15//! [dijkstra]: https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
16//! [sssp]: https://en.wikipedia.org/wiki/Shortest_path_problem
17//! [dir_graph]: https://en.wikipedia.org/wiki/Directed_graph
18//!
19//! ```
20//! use std::cmp::Ordering;
21//! use std::collections::BinaryHeap;
22//!
23//! #[derive(Copy, Clone, Eq, PartialEq)]
24//! struct State {
25//! cost: usize,
26//! position: usize,
27//! }
28//!
29//! // The priority queue depends on `Ord`.
30//! // Explicitly implement the trait so the queue becomes a min-heap
31//! // instead of a max-heap.
32//! impl Ord for State {
33//! fn cmp(&self, other: &Self) -> Ordering {
34//! // Notice that we flip the ordering on costs.
35//! // In case of a tie we compare positions - this step is necessary
36//! // to make implementations of `PartialEq` and `Ord` consistent.
37//! other.cost.cmp(&self.cost)
38//! .then_with(|| self.position.cmp(&other.position))
39//! }
40//! }
41//!
42//! // `PartialOrd` needs to be implemented as well.
43//! impl PartialOrd for State {
44//! fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
45//! Some(self.cmp(other))
46//! }
47//! }
48//!
49//! // Each node is represented as a `usize`, for a shorter implementation.
50//! struct Edge {
51//! node: usize,
52//! cost: usize,
53//! }
54//!
55//! // Dijkstra's shortest path algorithm.
56//!
57//! // Start at `start` and use `dist` to track the current shortest distance
58//! // to each node. This implementation isn't memory-efficient as it may leave duplicate
59//! // nodes in the queue. It also uses `usize::MAX` as a sentinel value,
60//! // for a simpler implementation.
61//! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> {
62//! // dist[node] = current shortest distance from `start` to `node`
63//! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect();
64//!
65//! let mut heap = BinaryHeap::new();
66//!
67//! // We're at `start`, with a zero cost
68//! dist[start] = 0;
69//! heap.push(State { cost: 0, position: start });
70//!
71//! // Examine the frontier with lower cost nodes first (min-heap)
72//! while let Some(State { cost, position }) = heap.pop() {
73//! // Alternatively we could have continued to find all shortest paths
74//! if position == goal { return Some(cost); }
75//!
76//! // Important as we may have already found a better way
77//! if cost > dist[position] { continue; }
78//!
79//! // For each node we can reach, see if we can find a way with
80//! // a lower cost going through this node
81//! for edge in &adj_list[position] {
82//! let next = State { cost: cost + edge.cost, position: edge.node };
83//!
84//! // If so, add it to the frontier and continue
85//! if next.cost < dist[next.position] {
86//! heap.push(next);
87//! // Relaxation, we have now found a better way
88//! dist[next.position] = next.cost;
89//! }
90//! }
91//! }
92//!
93//! // Goal not reachable
94//! None
95//! }
96//!
97//! fn main() {
98//! // This is the directed graph we're going to use.
99//! // The node numbers correspond to the different states,
100//! // and the edge weights symbolize the cost of moving
101//! // from one node to another.
102//! // Note that the edges are one-way.
103//! //
104//! // 7
105//! // +-----------------+
106//! // | |
107//! // v 1 2 | 2
108//! // 0 -----> 1 -----> 3 ---> 4
109//! // | ^ ^ ^
110//! // | | 1 | |
111//! // | | | 3 | 1
112//! // +------> 2 -------+ |
113//! // 10 | |
114//! // +---------------+
115//! //
116//! // The graph is represented as an adjacency list where each index,
117//! // corresponding to a node value, has a list of outgoing edges.
118//! // Chosen for its efficiency.
119//! let graph = vec![
120//! // Node 0
121//! vec![Edge { node: 2, cost: 10 },
122//! Edge { node: 1, cost: 1 }],
123//! // Node 1
124//! vec![Edge { node: 3, cost: 2 }],
125//! // Node 2
126//! vec![Edge { node: 1, cost: 1 },
127//! Edge { node: 3, cost: 3 },
128//! Edge { node: 4, cost: 1 }],
129//! // Node 3
130//! vec![Edge { node: 0, cost: 7 },
131//! Edge { node: 4, cost: 2 }],
132//! // Node 4
133//! vec![]];
134//!
135//! assert_eq!(shortest_path(&graph, 0, 1), Some(1));
136//! assert_eq!(shortest_path(&graph, 0, 3), Some(3));
137//! assert_eq!(shortest_path(&graph, 3, 0), Some(7));
138//! assert_eq!(shortest_path(&graph, 0, 4), Some(5));
139//! assert_eq!(shortest_path(&graph, 4, 0), None);
140//! }
141//! ```
142
143#![allow(missing_docs)]
144#![stable(feature = "rust1", since = "1.0.0")]
145
146use core::alloc::Allocator;
147use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedFused, TrustedLen};
148use core::mem::{self, ManuallyDrop, swap};
149use core::num::NonZero;
150use core::ops::{Deref, DerefMut};
151use core::{fmt, ptr};
152
153use crate::alloc::Global;
154use crate::collections::TryReserveError;
155use crate::slice;
156#[cfg(not(test))]
157use crate::vec::AsVecIntoIter;
158use crate::vec::{self, Vec};
159
160/// A priority queue implemented with a binary heap.
161///
162/// This will be a max-heap.
163///
164/// It is a logic error for an item to be modified in such a way that the
165/// item's ordering relative to any other item, as determined by the [`Ord`]
166/// trait, changes while it is in the heap. This is normally only possible
167/// through interior mutability, global state, I/O, or unsafe code. The
168/// behavior resulting from such a logic error is not specified, but will
169/// be encapsulated to the `BinaryHeap` that observed the logic error and not
170/// result in undefined behavior. This could include panics, incorrect results,
171/// aborts, memory leaks, and non-termination.
172///
173/// As long as no elements change their relative order while being in the heap
174/// as described above, the API of `BinaryHeap` guarantees that the heap
175/// invariant remains intact i.e. its methods all behave as documented. For
176/// example if a method is documented as iterating in sorted order, that's
177/// guaranteed to work as long as elements in the heap have not changed order,
178/// even in the presence of closures getting unwinded out of, iterators getting
179/// leaked, and similar foolishness.
180///
181/// # Examples
182///
183/// ```
184/// use std::collections::BinaryHeap;
185///
186/// // Type inference lets us omit an explicit type signature (which
187/// // would be `BinaryHeap<i32>` in this example).
188/// let mut heap = BinaryHeap::new();
189///
190/// // We can use peek to look at the next item in the heap. In this case,
191/// // there's no items in there yet so we get None.
192/// assert_eq!(heap.peek(), None);
193///
194/// // Let's add some scores...
195/// heap.push(1);
196/// heap.push(5);
197/// heap.push(2);
198///
199/// // Now peek shows the most important item in the heap.
200/// assert_eq!(heap.peek(), Some(&5));
201///
202/// // We can check the length of a heap.
203/// assert_eq!(heap.len(), 3);
204///
205/// // We can iterate over the items in the heap, although they are returned in
206/// // a random order.
207/// for x in &heap {
208/// println!("{x}");
209/// }
210///
211/// // If we instead pop these scores, they should come back in order.
212/// assert_eq!(heap.pop(), Some(5));
213/// assert_eq!(heap.pop(), Some(2));
214/// assert_eq!(heap.pop(), Some(1));
215/// assert_eq!(heap.pop(), None);
216///
217/// // We can clear the heap of any remaining items.
218/// heap.clear();
219///
220/// // The heap should now be empty.
221/// assert!(heap.is_empty())
222/// ```
223///
224/// A `BinaryHeap` with a known list of items can be initialized from an array:
225///
226/// ```
227/// use std::collections::BinaryHeap;
228///
229/// let heap = BinaryHeap::from([1, 5, 2]);
230/// ```
231///
232/// ## Min-heap
233///
234/// Either [`core::cmp::Reverse`] or a custom [`Ord`] implementation can be used to
235/// make `BinaryHeap` a min-heap. This makes `heap.pop()` return the smallest
236/// value instead of the greatest one.
237///
238/// ```
239/// use std::collections::BinaryHeap;
240/// use std::cmp::Reverse;
241///
242/// let mut heap = BinaryHeap::new();
243///
244/// // Wrap values in `Reverse`
245/// heap.push(Reverse(1));
246/// heap.push(Reverse(5));
247/// heap.push(Reverse(2));
248///
249/// // If we pop these scores now, they should come back in the reverse order.
250/// assert_eq!(heap.pop(), Some(Reverse(1)));
251/// assert_eq!(heap.pop(), Some(Reverse(2)));
252/// assert_eq!(heap.pop(), Some(Reverse(5)));
253/// assert_eq!(heap.pop(), None);
254/// ```
255///
256/// # Time complexity
257///
258/// | [push] | [pop] | [peek]/[peek\_mut] |
259/// |---------|---------------|--------------------|
260/// | *O*(1)~ | *O*(log(*n*)) | *O*(1) |
261///
262/// The value for `push` is an expected cost; the method documentation gives a
263/// more detailed analysis.
264///
265/// [`core::cmp::Reverse`]: core::cmp::Reverse
266/// [`Cell`]: core::cell::Cell
267/// [`RefCell`]: core::cell::RefCell
268/// [push]: BinaryHeap::push
269/// [pop]: BinaryHeap::pop
270/// [peek]: BinaryHeap::peek
271/// [peek\_mut]: BinaryHeap::peek_mut
272#[stable(feature = "rust1", since = "1.0.0")]
273#[cfg_attr(not(test), rustc_diagnostic_item = "BinaryHeap")]
274pub struct BinaryHeap<
275 T,
276 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
277> {
278 data: Vec<T, A>,
279}
280
281/// Structure wrapping a mutable reference to the greatest item on a
282/// `BinaryHeap`.
283///
284/// This `struct` is created by the [`peek_mut`] method on [`BinaryHeap`]. See
285/// its documentation for more.
286///
287/// [`peek_mut`]: BinaryHeap::peek_mut
288#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
289pub struct PeekMut<
290 'a,
291 T: 'a + Ord,
292 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
293> {
294 heap: &'a mut BinaryHeap<T, A>,
295 // If a set_len + sift_down are required, this is Some. If a &mut T has not
296 // yet been exposed to peek_mut()'s caller, it's None.
297 original_len: Option<NonZero<usize>>,
298}
299
300#[stable(feature = "collection_debug", since = "1.17.0")]
301impl<T: Ord + fmt::Debug, A: Allocator> fmt::Debug for PeekMut<'_, T, A> {
302 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
303 f.debug_tuple(name:"PeekMut").field(&self.heap.data[0]).finish()
304 }
305}
306
307#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
308impl<T: Ord, A: Allocator> Drop for PeekMut<'_, T, A> {
309 fn drop(&mut self) {
310 if let Some(original_len: NonZero) = self.original_len {
311 // SAFETY: That's how many elements were in the Vec at the time of
312 // the PeekMut::deref_mut call, and therefore also at the time of
313 // the BinaryHeap::peek_mut call. Since the PeekMut did not end up
314 // getting leaked, we are now undoing the leak amplification that
315 // the DerefMut prepared for.
316 unsafe { self.heap.data.set_len(new_len:original_len.get()) };
317
318 // SAFETY: PeekMut is only instantiated for non-empty heaps.
319 unsafe { self.heap.sift_down(pos:0) };
320 }
321 }
322}
323
324#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
325impl<T: Ord, A: Allocator> Deref for PeekMut<'_, T, A> {
326 type Target = T;
327 fn deref(&self) -> &T {
328 debug_assert!(!self.heap.is_empty());
329 // SAFE: PeekMut is only instantiated for non-empty heaps
330 unsafe { self.heap.data.get_unchecked(index:0) }
331 }
332}
333
334#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
335impl<T: Ord, A: Allocator> DerefMut for PeekMut<'_, T, A> {
336 fn deref_mut(&mut self) -> &mut T {
337 debug_assert!(!self.heap.is_empty());
338
339 let len = self.heap.len();
340 if len > 1 {
341 // Here we preemptively leak all the rest of the underlying vector
342 // after the currently max element. If the caller mutates the &mut T
343 // we're about to give them, and then leaks the PeekMut, all these
344 // elements will remain leaked. If they don't leak the PeekMut, then
345 // either Drop or PeekMut::pop will un-leak the vector elements.
346 //
347 // This is technique is described throughout several other places in
348 // the standard library as "leak amplification".
349 unsafe {
350 // SAFETY: len > 1 so len != 0.
351 self.original_len = Some(NonZero::new_unchecked(len));
352 // SAFETY: len > 1 so all this does for now is leak elements,
353 // which is safe.
354 self.heap.data.set_len(1);
355 }
356 }
357
358 // SAFE: PeekMut is only instantiated for non-empty heaps
359 unsafe { self.heap.data.get_unchecked_mut(0) }
360 }
361}
362
363impl<'a, T: Ord, A: Allocator> PeekMut<'a, T, A> {
364 /// Sifts the current element to its new position.
365 ///
366 /// Afterwards refers to the new element. Returns if the element changed.
367 ///
368 /// ## Examples
369 ///
370 /// The condition can be used to upper bound all elements in the heap. When only few elements
371 /// are affected, the heap's sort ensures this is faster than a reconstruction from the raw
372 /// element list and requires no additional allocation.
373 ///
374 /// ```
375 /// #![feature(binary_heap_peek_mut_refresh)]
376 /// use std::collections::BinaryHeap;
377 ///
378 /// let mut heap: BinaryHeap<u32> = (0..128).collect();
379 /// let mut peek = heap.peek_mut().unwrap();
380 ///
381 /// loop {
382 /// *peek = 99;
383 ///
384 /// if !peek.refresh() {
385 /// break;
386 /// }
387 /// }
388 ///
389 /// // Post condition, this is now an upper bound.
390 /// assert!(*peek < 100);
391 /// ```
392 ///
393 /// When the element remains the maximum after modification, the peek remains unchanged:
394 ///
395 /// ```
396 /// #![feature(binary_heap_peek_mut_refresh)]
397 /// use std::collections::BinaryHeap;
398 ///
399 /// let mut heap: BinaryHeap<u32> = [1, 2, 3].into();
400 /// let mut peek = heap.peek_mut().unwrap();
401 ///
402 /// assert_eq!(*peek, 3);
403 /// *peek = 42;
404 ///
405 /// // When we refresh, the peek is updated to the new maximum.
406 /// assert!(!peek.refresh(), "42 is even larger than 3");
407 /// assert_eq!(*peek, 42);
408 /// ```
409 #[unstable(feature = "binary_heap_peek_mut_refresh", issue = "138355")]
410 #[must_use = "is equivalent to dropping and getting a new PeekMut except for return information"]
411 pub fn refresh(&mut self) -> bool {
412 // The length of the underlying heap is unchanged by sifting down. The value stored for leak
413 // amplification thus remains accurate. We erase the leak amplification firstly because the
414 // operation is then equivalent to constructing a new PeekMut and secondly this avoids any
415 // future complication where original_len being non-empty would be interpreted as the heap
416 // having been leak amplified instead of checking the heap itself.
417 if let Some(original_len) = self.original_len.take() {
418 // SAFETY: This is how many elements were in the Vec at the time of
419 // the BinaryHeap::peek_mut call.
420 unsafe { self.heap.data.set_len(original_len.get()) };
421
422 // The length of the heap did not change by sifting, upholding our own invariants.
423
424 // SAFETY: PeekMut is only instantiated for non-empty heaps.
425 (unsafe { self.heap.sift_down(0) }) != 0
426 } else {
427 // The element was not modified.
428 false
429 }
430 }
431
432 /// Removes the peeked value from the heap and returns it.
433 #[stable(feature = "binary_heap_peek_mut_pop", since = "1.18.0")]
434 pub fn pop(mut this: PeekMut<'a, T, A>) -> T {
435 if let Some(original_len) = this.original_len.take() {
436 // SAFETY: This is how many elements were in the Vec at the time of
437 // the BinaryHeap::peek_mut call.
438 unsafe { this.heap.data.set_len(original_len.get()) };
439
440 // Unlike in Drop, here we don't also need to do a sift_down even if
441 // the caller could've mutated the element. It is removed from the
442 // heap on the next line and pop() is not sensitive to its value.
443 }
444
445 // SAFETY: Have a `PeekMut` element proves that the associated binary heap being non-empty,
446 // so the `pop` operation will not fail.
447 unsafe { this.heap.pop().unwrap_unchecked() }
448 }
449}
450
451#[stable(feature = "rust1", since = "1.0.0")]
452impl<T: Clone, A: Allocator + Clone> Clone for BinaryHeap<T, A> {
453 fn clone(&self) -> Self {
454 BinaryHeap { data: self.data.clone() }
455 }
456
457 /// Overwrites the contents of `self` with a clone of the contents of `source`.
458 ///
459 /// This method is preferred over simply assigning `source.clone()` to `self`,
460 /// as it avoids reallocation if possible.
461 ///
462 /// See [`Vec::clone_from()`] for more details.
463 fn clone_from(&mut self, source: &Self) {
464 self.data.clone_from(&source.data);
465 }
466}
467
468#[stable(feature = "rust1", since = "1.0.0")]
469impl<T: Ord> Default for BinaryHeap<T> {
470 /// Creates an empty `BinaryHeap<T>`.
471 #[inline]
472 fn default() -> BinaryHeap<T> {
473 BinaryHeap::new()
474 }
475}
476
477#[stable(feature = "binaryheap_debug", since = "1.4.0")]
478impl<T: fmt::Debug, A: Allocator> fmt::Debug for BinaryHeap<T, A> {
479 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
480 f.debug_list().entries(self.iter()).finish()
481 }
482}
483
484struct RebuildOnDrop<
485 'a,
486 T: Ord,
487 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
488> {
489 heap: &'a mut BinaryHeap<T, A>,
490 rebuild_from: usize,
491}
492
493impl<T: Ord, A: Allocator> Drop for RebuildOnDrop<'_, T, A> {
494 fn drop(&mut self) {
495 self.heap.rebuild_tail(self.rebuild_from);
496 }
497}
498
499impl<T: Ord> BinaryHeap<T> {
500 /// Creates an empty `BinaryHeap` as a max-heap.
501 ///
502 /// # Examples
503 ///
504 /// Basic usage:
505 ///
506 /// ```
507 /// use std::collections::BinaryHeap;
508 /// let mut heap = BinaryHeap::new();
509 /// heap.push(4);
510 /// ```
511 #[stable(feature = "rust1", since = "1.0.0")]
512 #[rustc_const_stable(feature = "const_binary_heap_constructor", since = "1.80.0")]
513 #[must_use]
514 pub const fn new() -> BinaryHeap<T> {
515 BinaryHeap { data: vec![] }
516 }
517
518 /// Creates an empty `BinaryHeap` with at least the specified capacity.
519 ///
520 /// The binary heap will be able to hold at least `capacity` elements without
521 /// reallocating. This method is allowed to allocate for more elements than
522 /// `capacity`. If `capacity` is zero, the binary heap will not allocate.
523 ///
524 /// # Examples
525 ///
526 /// Basic usage:
527 ///
528 /// ```
529 /// use std::collections::BinaryHeap;
530 /// let mut heap = BinaryHeap::with_capacity(10);
531 /// heap.push(4);
532 /// ```
533 #[stable(feature = "rust1", since = "1.0.0")]
534 #[must_use]
535 pub fn with_capacity(capacity: usize) -> BinaryHeap<T> {
536 BinaryHeap { data: Vec::with_capacity(capacity) }
537 }
538}
539
540impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
541 /// Creates an empty `BinaryHeap` as a max-heap, using `A` as allocator.
542 ///
543 /// # Examples
544 ///
545 /// Basic usage:
546 ///
547 /// ```
548 /// #![feature(allocator_api)]
549 ///
550 /// use std::alloc::System;
551 /// use std::collections::BinaryHeap;
552 /// let mut heap = BinaryHeap::new_in(System);
553 /// heap.push(4);
554 /// ```
555 #[unstable(feature = "allocator_api", issue = "32838")]
556 #[must_use]
557 pub const fn new_in(alloc: A) -> BinaryHeap<T, A> {
558 BinaryHeap { data: Vec::new_in(alloc) }
559 }
560
561 /// Creates an empty `BinaryHeap` with at least the specified capacity, using `A` as allocator.
562 ///
563 /// The binary heap will be able to hold at least `capacity` elements without
564 /// reallocating. This method is allowed to allocate for more elements than
565 /// `capacity`. If `capacity` is zero, the binary heap will not allocate.
566 ///
567 /// # Examples
568 ///
569 /// Basic usage:
570 ///
571 /// ```
572 /// #![feature(allocator_api)]
573 ///
574 /// use std::alloc::System;
575 /// use std::collections::BinaryHeap;
576 /// let mut heap = BinaryHeap::with_capacity_in(10, System);
577 /// heap.push(4);
578 /// ```
579 #[unstable(feature = "allocator_api", issue = "32838")]
580 #[must_use]
581 pub fn with_capacity_in(capacity: usize, alloc: A) -> BinaryHeap<T, A> {
582 BinaryHeap { data: Vec::with_capacity_in(capacity, alloc) }
583 }
584
585 /// Returns a mutable reference to the greatest item in the binary heap, or
586 /// `None` if it is empty.
587 ///
588 /// Note: If the `PeekMut` value is leaked, some heap elements might get
589 /// leaked along with it, but the remaining elements will remain a valid
590 /// heap.
591 ///
592 /// # Examples
593 ///
594 /// Basic usage:
595 ///
596 /// ```
597 /// use std::collections::BinaryHeap;
598 /// let mut heap = BinaryHeap::new();
599 /// assert!(heap.peek_mut().is_none());
600 ///
601 /// heap.push(1);
602 /// heap.push(5);
603 /// heap.push(2);
604 /// if let Some(mut val) = heap.peek_mut() {
605 /// *val = 0;
606 /// }
607 /// assert_eq!(heap.peek(), Some(&2));
608 /// ```
609 ///
610 /// # Time complexity
611 ///
612 /// If the item is modified then the worst case time complexity is *O*(log(*n*)),
613 /// otherwise it's *O*(1).
614 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
615 pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T, A>> {
616 if self.is_empty() { None } else { Some(PeekMut { heap: self, original_len: None }) }
617 }
618
619 /// Removes the greatest item from the binary heap and returns it, or `None` if it
620 /// is empty.
621 ///
622 /// # Examples
623 ///
624 /// Basic usage:
625 ///
626 /// ```
627 /// use std::collections::BinaryHeap;
628 /// let mut heap = BinaryHeap::from([1, 3]);
629 ///
630 /// assert_eq!(heap.pop(), Some(3));
631 /// assert_eq!(heap.pop(), Some(1));
632 /// assert_eq!(heap.pop(), None);
633 /// ```
634 ///
635 /// # Time complexity
636 ///
637 /// The worst case cost of `pop` on a heap containing *n* elements is *O*(log(*n*)).
638 #[stable(feature = "rust1", since = "1.0.0")]
639 pub fn pop(&mut self) -> Option<T> {
640 self.data.pop().map(|mut item| {
641 if !self.is_empty() {
642 swap(&mut item, &mut self.data[0]);
643 // SAFETY: !self.is_empty() means that self.len() > 0
644 unsafe { self.sift_down_to_bottom(0) };
645 }
646 item
647 })
648 }
649
650 /// Pushes an item onto the binary heap.
651 ///
652 /// # Examples
653 ///
654 /// Basic usage:
655 ///
656 /// ```
657 /// use std::collections::BinaryHeap;
658 /// let mut heap = BinaryHeap::new();
659 /// heap.push(3);
660 /// heap.push(5);
661 /// heap.push(1);
662 ///
663 /// assert_eq!(heap.len(), 3);
664 /// assert_eq!(heap.peek(), Some(&5));
665 /// ```
666 ///
667 /// # Time complexity
668 ///
669 /// The expected cost of `push`, averaged over every possible ordering of
670 /// the elements being pushed, and over a sufficiently large number of
671 /// pushes, is *O*(1). This is the most meaningful cost metric when pushing
672 /// elements that are *not* already in any sorted pattern.
673 ///
674 /// The time complexity degrades if elements are pushed in predominantly
675 /// ascending order. In the worst case, elements are pushed in ascending
676 /// sorted order and the amortized cost per push is *O*(log(*n*)) against a heap
677 /// containing *n* elements.
678 ///
679 /// The worst case cost of a *single* call to `push` is *O*(*n*). The worst case
680 /// occurs when capacity is exhausted and needs a resize. The resize cost
681 /// has been amortized in the previous figures.
682 #[stable(feature = "rust1", since = "1.0.0")]
683 #[rustc_confusables("append", "put")]
684 pub fn push(&mut self, item: T) {
685 let old_len = self.len();
686 self.data.push(item);
687 // SAFETY: Since we pushed a new item it means that
688 // old_len = self.len() - 1 < self.len()
689 unsafe { self.sift_up(0, old_len) };
690 }
691
692 /// Consumes the `BinaryHeap` and returns a vector in sorted
693 /// (ascending) order.
694 ///
695 /// # Examples
696 ///
697 /// Basic usage:
698 ///
699 /// ```
700 /// use std::collections::BinaryHeap;
701 ///
702 /// let mut heap = BinaryHeap::from([1, 2, 4, 5, 7]);
703 /// heap.push(6);
704 /// heap.push(3);
705 ///
706 /// let vec = heap.into_sorted_vec();
707 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);
708 /// ```
709 #[must_use = "`self` will be dropped if the result is not used"]
710 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
711 pub fn into_sorted_vec(mut self) -> Vec<T, A> {
712 let mut end = self.len();
713 while end > 1 {
714 end -= 1;
715 // SAFETY: `end` goes from `self.len() - 1` to 1 (both included),
716 // so it's always a valid index to access.
717 // It is safe to access index 0 (i.e. `ptr`), because
718 // 1 <= end < self.len(), which means self.len() >= 2.
719 unsafe {
720 let ptr = self.data.as_mut_ptr();
721 ptr::swap(ptr, ptr.add(end));
722 }
723 // SAFETY: `end` goes from `self.len() - 1` to 1 (both included) so:
724 // 0 < 1 <= end <= self.len() - 1 < self.len()
725 // Which means 0 < end and end < self.len().
726 unsafe { self.sift_down_range(0, end) };
727 }
728 self.into_vec()
729 }
730
731 // The implementations of sift_up and sift_down use unsafe blocks in
732 // order to move an element out of the vector (leaving behind a
733 // hole), shift along the others and move the removed element back into the
734 // vector at the final location of the hole.
735 // The `Hole` type is used to represent this, and make sure
736 // the hole is filled back at the end of its scope, even on panic.
737 // Using a hole reduces the constant factor compared to using swaps,
738 // which involves twice as many moves.
739
740 /// # Safety
741 ///
742 /// The caller must guarantee that `pos < self.len()`.
743 ///
744 /// Returns the new position of the element.
745 unsafe fn sift_up(&mut self, start: usize, pos: usize) -> usize {
746 // Take out the value at `pos` and create a hole.
747 // SAFETY: The caller guarantees that pos < self.len()
748 let mut hole = unsafe { Hole::new(&mut self.data, pos) };
749
750 while hole.pos() > start {
751 let parent = (hole.pos() - 1) / 2;
752
753 // SAFETY: hole.pos() > start >= 0, which means hole.pos() > 0
754 // and so hole.pos() - 1 can't underflow.
755 // This guarantees that parent < hole.pos() so
756 // it's a valid index and also != hole.pos().
757 if hole.element() <= unsafe { hole.get(parent) } {
758 break;
759 }
760
761 // SAFETY: Same as above
762 unsafe { hole.move_to(parent) };
763 }
764
765 hole.pos()
766 }
767
768 /// Take an element at `pos` and move it down the heap,
769 /// while its children are larger.
770 ///
771 /// Returns the new position of the element.
772 ///
773 /// # Safety
774 ///
775 /// The caller must guarantee that `pos < end <= self.len()`.
776 unsafe fn sift_down_range(&mut self, pos: usize, end: usize) -> usize {
777 // SAFETY: The caller guarantees that pos < end <= self.len().
778 let mut hole = unsafe { Hole::new(&mut self.data, pos) };
779 let mut child = 2 * hole.pos() + 1;
780
781 // Loop invariant: child == 2 * hole.pos() + 1.
782 while child <= end.saturating_sub(2) {
783 // compare with the greater of the two children
784 // SAFETY: child < end - 1 < self.len() and
785 // child + 1 < end <= self.len(), so they're valid indexes.
786 // child == 2 * hole.pos() + 1 != hole.pos() and
787 // child + 1 == 2 * hole.pos() + 2 != hole.pos().
788 // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow
789 // if T is a ZST
790 child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize;
791
792 // if we are already in order, stop.
793 // SAFETY: child is now either the old child or the old child+1
794 // We already proven that both are < self.len() and != hole.pos()
795 if hole.element() >= unsafe { hole.get(child) } {
796 return hole.pos();
797 }
798
799 // SAFETY: same as above.
800 unsafe { hole.move_to(child) };
801 child = 2 * hole.pos() + 1;
802 }
803
804 // SAFETY: && short circuit, which means that in the
805 // second condition it's already true that child == end - 1 < self.len().
806 if child == end - 1 && hole.element() < unsafe { hole.get(child) } {
807 // SAFETY: child is already proven to be a valid index and
808 // child == 2 * hole.pos() + 1 != hole.pos().
809 unsafe { hole.move_to(child) };
810 }
811
812 hole.pos()
813 }
814
815 /// # Safety
816 ///
817 /// The caller must guarantee that `pos < self.len()`.
818 unsafe fn sift_down(&mut self, pos: usize) -> usize {
819 let len = self.len();
820 // SAFETY: pos < len is guaranteed by the caller and
821 // obviously len = self.len() <= self.len().
822 unsafe { self.sift_down_range(pos, len) }
823 }
824
825 /// Take an element at `pos` and move it all the way down the heap,
826 /// then sift it up to its position.
827 ///
828 /// Note: This is faster when the element is known to be large / should
829 /// be closer to the bottom.
830 ///
831 /// # Safety
832 ///
833 /// The caller must guarantee that `pos < self.len()`.
834 unsafe fn sift_down_to_bottom(&mut self, mut pos: usize) {
835 let end = self.len();
836 let start = pos;
837
838 // SAFETY: The caller guarantees that pos < self.len().
839 let mut hole = unsafe { Hole::new(&mut self.data, pos) };
840 let mut child = 2 * hole.pos() + 1;
841
842 // Loop invariant: child == 2 * hole.pos() + 1.
843 while child <= end.saturating_sub(2) {
844 // SAFETY: child < end - 1 < self.len() and
845 // child + 1 < end <= self.len(), so they're valid indexes.
846 // child == 2 * hole.pos() + 1 != hole.pos() and
847 // child + 1 == 2 * hole.pos() + 2 != hole.pos().
848 // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow
849 // if T is a ZST
850 child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize;
851
852 // SAFETY: Same as above
853 unsafe { hole.move_to(child) };
854 child = 2 * hole.pos() + 1;
855 }
856
857 if child == end - 1 {
858 // SAFETY: child == end - 1 < self.len(), so it's a valid index
859 // and child == 2 * hole.pos() + 1 != hole.pos().
860 unsafe { hole.move_to(child) };
861 }
862 pos = hole.pos();
863 drop(hole);
864
865 // SAFETY: pos is the position in the hole and was already proven
866 // to be a valid index.
867 unsafe { self.sift_up(start, pos) };
868 }
869
870 /// Rebuild assuming data[0..start] is still a proper heap.
871 fn rebuild_tail(&mut self, start: usize) {
872 if start == self.len() {
873 return;
874 }
875
876 let tail_len = self.len() - start;
877
878 #[inline(always)]
879 fn log2_fast(x: usize) -> usize {
880 (usize::BITS - x.leading_zeros() - 1) as usize
881 }
882
883 // `rebuild` takes O(self.len()) operations
884 // and about 2 * self.len() comparisons in the worst case
885 // while repeating `sift_up` takes O(tail_len * log(start)) operations
886 // and about 1 * tail_len * log_2(start) comparisons in the worst case,
887 // assuming start >= tail_len. For larger heaps, the crossover point
888 // no longer follows this reasoning and was determined empirically.
889 let better_to_rebuild = if start < tail_len {
890 true
891 } else if self.len() <= 2048 {
892 2 * self.len() < tail_len * log2_fast(start)
893 } else {
894 2 * self.len() < tail_len * 11
895 };
896
897 if better_to_rebuild {
898 self.rebuild();
899 } else {
900 for i in start..self.len() {
901 // SAFETY: The index `i` is always less than self.len().
902 unsafe { self.sift_up(0, i) };
903 }
904 }
905 }
906
907 fn rebuild(&mut self) {
908 let mut n = self.len() / 2;
909 while n > 0 {
910 n -= 1;
911 // SAFETY: n starts from self.len() / 2 and goes down to 0.
912 // The only case when !(n < self.len()) is if
913 // self.len() == 0, but it's ruled out by the loop condition.
914 unsafe { self.sift_down(n) };
915 }
916 }
917
918 /// Moves all the elements of `other` into `self`, leaving `other` empty.
919 ///
920 /// # Examples
921 ///
922 /// Basic usage:
923 ///
924 /// ```
925 /// use std::collections::BinaryHeap;
926 ///
927 /// let mut a = BinaryHeap::from([-10, 1, 2, 3, 3]);
928 /// let mut b = BinaryHeap::from([-20, 5, 43]);
929 ///
930 /// a.append(&mut b);
931 ///
932 /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
933 /// assert!(b.is_empty());
934 /// ```
935 #[stable(feature = "binary_heap_append", since = "1.11.0")]
936 pub fn append(&mut self, other: &mut Self) {
937 if self.len() < other.len() {
938 swap(self, other);
939 }
940
941 let start = self.data.len();
942
943 self.data.append(&mut other.data);
944
945 self.rebuild_tail(start);
946 }
947
948 /// Clears the binary heap, returning an iterator over the removed elements
949 /// in heap order. If the iterator is dropped before being fully consumed,
950 /// it drops the remaining elements in heap order.
951 ///
952 /// The returned iterator keeps a mutable borrow on the heap to optimize
953 /// its implementation.
954 ///
955 /// Note:
956 /// * `.drain_sorted()` is *O*(*n* \* log(*n*)); much slower than `.drain()`.
957 /// You should use the latter for most cases.
958 ///
959 /// # Examples
960 ///
961 /// Basic usage:
962 ///
963 /// ```
964 /// #![feature(binary_heap_drain_sorted)]
965 /// use std::collections::BinaryHeap;
966 ///
967 /// let mut heap = BinaryHeap::from([1, 2, 3, 4, 5]);
968 /// assert_eq!(heap.len(), 5);
969 ///
970 /// drop(heap.drain_sorted()); // removes all elements in heap order
971 /// assert_eq!(heap.len(), 0);
972 /// ```
973 #[inline]
974 #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
975 pub fn drain_sorted(&mut self) -> DrainSorted<'_, T, A> {
976 DrainSorted { inner: self }
977 }
978
979 /// Retains only the elements specified by the predicate.
980 ///
981 /// In other words, remove all elements `e` for which `f(&e)` returns
982 /// `false`. The elements are visited in unsorted (and unspecified) order.
983 ///
984 /// # Examples
985 ///
986 /// Basic usage:
987 ///
988 /// ```
989 /// use std::collections::BinaryHeap;
990 ///
991 /// let mut heap = BinaryHeap::from([-10, -5, 1, 2, 4, 13]);
992 ///
993 /// heap.retain(|x| x % 2 == 0); // only keep even numbers
994 ///
995 /// assert_eq!(heap.into_sorted_vec(), [-10, 2, 4])
996 /// ```
997 #[stable(feature = "binary_heap_retain", since = "1.70.0")]
998 pub fn retain<F>(&mut self, mut f: F)
999 where
1000 F: FnMut(&T) -> bool,
1001 {
1002 // rebuild_start will be updated to the first touched element below, and the rebuild will
1003 // only be done for the tail.
1004 let mut guard = RebuildOnDrop { rebuild_from: self.len(), heap: self };
1005 let mut i = 0;
1006
1007 guard.heap.data.retain(|e| {
1008 let keep = f(e);
1009 if !keep && i < guard.rebuild_from {
1010 guard.rebuild_from = i;
1011 }
1012 i += 1;
1013 keep
1014 });
1015 }
1016}
1017
1018impl<T, A: Allocator> BinaryHeap<T, A> {
1019 /// Returns an iterator visiting all values in the underlying vector, in
1020 /// arbitrary order.
1021 ///
1022 /// # Examples
1023 ///
1024 /// Basic usage:
1025 ///
1026 /// ```
1027 /// use std::collections::BinaryHeap;
1028 /// let heap = BinaryHeap::from([1, 2, 3, 4]);
1029 ///
1030 /// // Print 1, 2, 3, 4 in arbitrary order
1031 /// for x in heap.iter() {
1032 /// println!("{x}");
1033 /// }
1034 /// ```
1035 #[stable(feature = "rust1", since = "1.0.0")]
1036 #[cfg_attr(not(test), rustc_diagnostic_item = "binaryheap_iter")]
1037 pub fn iter(&self) -> Iter<'_, T> {
1038 Iter { iter: self.data.iter() }
1039 }
1040
1041 /// Returns an iterator which retrieves elements in heap order.
1042 ///
1043 /// This method consumes the original heap.
1044 ///
1045 /// # Examples
1046 ///
1047 /// Basic usage:
1048 ///
1049 /// ```
1050 /// #![feature(binary_heap_into_iter_sorted)]
1051 /// use std::collections::BinaryHeap;
1052 /// let heap = BinaryHeap::from([1, 2, 3, 4, 5]);
1053 ///
1054 /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), [5, 4]);
1055 /// ```
1056 #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
1057 pub fn into_iter_sorted(self) -> IntoIterSorted<T, A> {
1058 IntoIterSorted { inner: self }
1059 }
1060
1061 /// Returns the greatest item in the binary heap, or `None` if it is empty.
1062 ///
1063 /// # Examples
1064 ///
1065 /// Basic usage:
1066 ///
1067 /// ```
1068 /// use std::collections::BinaryHeap;
1069 /// let mut heap = BinaryHeap::new();
1070 /// assert_eq!(heap.peek(), None);
1071 ///
1072 /// heap.push(1);
1073 /// heap.push(5);
1074 /// heap.push(2);
1075 /// assert_eq!(heap.peek(), Some(&5));
1076 ///
1077 /// ```
1078 ///
1079 /// # Time complexity
1080 ///
1081 /// Cost is *O*(1) in the worst case.
1082 #[must_use]
1083 #[stable(feature = "rust1", since = "1.0.0")]
1084 pub fn peek(&self) -> Option<&T> {
1085 self.data.get(0)
1086 }
1087
1088 /// Returns the number of elements the binary heap can hold without reallocating.
1089 ///
1090 /// # Examples
1091 ///
1092 /// Basic usage:
1093 ///
1094 /// ```
1095 /// use std::collections::BinaryHeap;
1096 /// let mut heap = BinaryHeap::with_capacity(100);
1097 /// assert!(heap.capacity() >= 100);
1098 /// heap.push(4);
1099 /// ```
1100 #[must_use]
1101 #[stable(feature = "rust1", since = "1.0.0")]
1102 pub fn capacity(&self) -> usize {
1103 self.data.capacity()
1104 }
1105
1106 /// Reserves the minimum capacity for at least `additional` elements more than
1107 /// the current length. Unlike [`reserve`], this will not
1108 /// deliberately over-allocate to speculatively avoid frequent allocations.
1109 /// After calling `reserve_exact`, capacity will be greater than or equal to
1110 /// `self.len() + additional`. Does nothing if the capacity is already
1111 /// sufficient.
1112 ///
1113 /// [`reserve`]: BinaryHeap::reserve
1114 ///
1115 /// # Panics
1116 ///
1117 /// Panics if the new capacity overflows [`usize`].
1118 ///
1119 /// # Examples
1120 ///
1121 /// Basic usage:
1122 ///
1123 /// ```
1124 /// use std::collections::BinaryHeap;
1125 /// let mut heap = BinaryHeap::new();
1126 /// heap.reserve_exact(100);
1127 /// assert!(heap.capacity() >= 100);
1128 /// heap.push(4);
1129 /// ```
1130 ///
1131 /// [`reserve`]: BinaryHeap::reserve
1132 #[stable(feature = "rust1", since = "1.0.0")]
1133 pub fn reserve_exact(&mut self, additional: usize) {
1134 self.data.reserve_exact(additional);
1135 }
1136
1137 /// Reserves capacity for at least `additional` elements more than the
1138 /// current length. The allocator may reserve more space to speculatively
1139 /// avoid frequent allocations. After calling `reserve`,
1140 /// capacity will be greater than or equal to `self.len() + additional`.
1141 /// Does nothing if capacity is already sufficient.
1142 ///
1143 /// # Panics
1144 ///
1145 /// Panics if the new capacity overflows [`usize`].
1146 ///
1147 /// # Examples
1148 ///
1149 /// Basic usage:
1150 ///
1151 /// ```
1152 /// use std::collections::BinaryHeap;
1153 /// let mut heap = BinaryHeap::new();
1154 /// heap.reserve(100);
1155 /// assert!(heap.capacity() >= 100);
1156 /// heap.push(4);
1157 /// ```
1158 #[stable(feature = "rust1", since = "1.0.0")]
1159 pub fn reserve(&mut self, additional: usize) {
1160 self.data.reserve(additional);
1161 }
1162
1163 /// Tries to reserve the minimum capacity for at least `additional` elements
1164 /// more than the current length. Unlike [`try_reserve`], this will not
1165 /// deliberately over-allocate to speculatively avoid frequent allocations.
1166 /// After calling `try_reserve_exact`, capacity will be greater than or
1167 /// equal to `self.len() + additional` if it returns `Ok(())`.
1168 /// Does nothing if the capacity is already sufficient.
1169 ///
1170 /// Note that the allocator may give the collection more space than it
1171 /// requests. Therefore, capacity can not be relied upon to be precisely
1172 /// minimal. Prefer [`try_reserve`] if future insertions are expected.
1173 ///
1174 /// [`try_reserve`]: BinaryHeap::try_reserve
1175 ///
1176 /// # Errors
1177 ///
1178 /// If the capacity overflows, or the allocator reports a failure, then an error
1179 /// is returned.
1180 ///
1181 /// # Examples
1182 ///
1183 /// ```
1184 /// use std::collections::BinaryHeap;
1185 /// use std::collections::TryReserveError;
1186 ///
1187 /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> {
1188 /// let mut heap = BinaryHeap::new();
1189 ///
1190 /// // Pre-reserve the memory, exiting if we can't
1191 /// heap.try_reserve_exact(data.len())?;
1192 ///
1193 /// // Now we know this can't OOM in the middle of our complex work
1194 /// heap.extend(data.iter());
1195 ///
1196 /// Ok(heap.pop())
1197 /// }
1198 /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
1199 /// ```
1200 #[stable(feature = "try_reserve_2", since = "1.63.0")]
1201 pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
1202 self.data.try_reserve_exact(additional)
1203 }
1204
1205 /// Tries to reserve capacity for at least `additional` elements more than the
1206 /// current length. The allocator may reserve more space to speculatively
1207 /// avoid frequent allocations. After calling `try_reserve`, capacity will be
1208 /// greater than or equal to `self.len() + additional` if it returns
1209 /// `Ok(())`. Does nothing if capacity is already sufficient. This method
1210 /// preserves the contents even if an error occurs.
1211 ///
1212 /// # Errors
1213 ///
1214 /// If the capacity overflows, or the allocator reports a failure, then an error
1215 /// is returned.
1216 ///
1217 /// # Examples
1218 ///
1219 /// ```
1220 /// use std::collections::BinaryHeap;
1221 /// use std::collections::TryReserveError;
1222 ///
1223 /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> {
1224 /// let mut heap = BinaryHeap::new();
1225 ///
1226 /// // Pre-reserve the memory, exiting if we can't
1227 /// heap.try_reserve(data.len())?;
1228 ///
1229 /// // Now we know this can't OOM in the middle of our complex work
1230 /// heap.extend(data.iter());
1231 ///
1232 /// Ok(heap.pop())
1233 /// }
1234 /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?");
1235 /// ```
1236 #[stable(feature = "try_reserve_2", since = "1.63.0")]
1237 pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
1238 self.data.try_reserve(additional)
1239 }
1240
1241 /// Discards as much additional capacity as possible.
1242 ///
1243 /// # Examples
1244 ///
1245 /// Basic usage:
1246 ///
1247 /// ```
1248 /// use std::collections::BinaryHeap;
1249 /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
1250 ///
1251 /// assert!(heap.capacity() >= 100);
1252 /// heap.shrink_to_fit();
1253 /// assert!(heap.capacity() == 0);
1254 /// ```
1255 #[stable(feature = "rust1", since = "1.0.0")]
1256 pub fn shrink_to_fit(&mut self) {
1257 self.data.shrink_to_fit();
1258 }
1259
1260 /// Discards capacity with a lower bound.
1261 ///
1262 /// The capacity will remain at least as large as both the length
1263 /// and the supplied value.
1264 ///
1265 /// If the current capacity is less than the lower limit, this is a no-op.
1266 ///
1267 /// # Examples
1268 ///
1269 /// ```
1270 /// use std::collections::BinaryHeap;
1271 /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
1272 ///
1273 /// assert!(heap.capacity() >= 100);
1274 /// heap.shrink_to(10);
1275 /// assert!(heap.capacity() >= 10);
1276 /// ```
1277 #[inline]
1278 #[stable(feature = "shrink_to", since = "1.56.0")]
1279 pub fn shrink_to(&mut self, min_capacity: usize) {
1280 self.data.shrink_to(min_capacity)
1281 }
1282
1283 /// Returns a slice of all values in the underlying vector, in arbitrary
1284 /// order.
1285 ///
1286 /// # Examples
1287 ///
1288 /// Basic usage:
1289 ///
1290 /// ```
1291 /// use std::collections::BinaryHeap;
1292 /// use std::io::{self, Write};
1293 ///
1294 /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]);
1295 ///
1296 /// io::sink().write(heap.as_slice()).unwrap();
1297 /// ```
1298 #[must_use]
1299 #[stable(feature = "binary_heap_as_slice", since = "1.80.0")]
1300 pub fn as_slice(&self) -> &[T] {
1301 self.data.as_slice()
1302 }
1303
1304 /// Consumes the `BinaryHeap` and returns the underlying vector
1305 /// in arbitrary order.
1306 ///
1307 /// # Examples
1308 ///
1309 /// Basic usage:
1310 ///
1311 /// ```
1312 /// use std::collections::BinaryHeap;
1313 /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]);
1314 /// let vec = heap.into_vec();
1315 ///
1316 /// // Will print in some order
1317 /// for x in vec {
1318 /// println!("{x}");
1319 /// }
1320 /// ```
1321 #[must_use = "`self` will be dropped if the result is not used"]
1322 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
1323 pub fn into_vec(self) -> Vec<T, A> {
1324 self.into()
1325 }
1326
1327 /// Returns a reference to the underlying allocator.
1328 #[unstable(feature = "allocator_api", issue = "32838")]
1329 #[inline]
1330 pub fn allocator(&self) -> &A {
1331 self.data.allocator()
1332 }
1333
1334 /// Returns the length of the binary heap.
1335 ///
1336 /// # Examples
1337 ///
1338 /// Basic usage:
1339 ///
1340 /// ```
1341 /// use std::collections::BinaryHeap;
1342 /// let heap = BinaryHeap::from([1, 3]);
1343 ///
1344 /// assert_eq!(heap.len(), 2);
1345 /// ```
1346 #[must_use]
1347 #[stable(feature = "rust1", since = "1.0.0")]
1348 #[rustc_confusables("length", "size")]
1349 pub fn len(&self) -> usize {
1350 self.data.len()
1351 }
1352
1353 /// Checks if the binary heap is empty.
1354 ///
1355 /// # Examples
1356 ///
1357 /// Basic usage:
1358 ///
1359 /// ```
1360 /// use std::collections::BinaryHeap;
1361 /// let mut heap = BinaryHeap::new();
1362 ///
1363 /// assert!(heap.is_empty());
1364 ///
1365 /// heap.push(3);
1366 /// heap.push(5);
1367 /// heap.push(1);
1368 ///
1369 /// assert!(!heap.is_empty());
1370 /// ```
1371 #[must_use]
1372 #[stable(feature = "rust1", since = "1.0.0")]
1373 pub fn is_empty(&self) -> bool {
1374 self.len() == 0
1375 }
1376
1377 /// Clears the binary heap, returning an iterator over the removed elements
1378 /// in arbitrary order. If the iterator is dropped before being fully
1379 /// consumed, it drops the remaining elements in arbitrary order.
1380 ///
1381 /// The returned iterator keeps a mutable borrow on the heap to optimize
1382 /// its implementation.
1383 ///
1384 /// # Examples
1385 ///
1386 /// Basic usage:
1387 ///
1388 /// ```
1389 /// use std::collections::BinaryHeap;
1390 /// let mut heap = BinaryHeap::from([1, 3]);
1391 ///
1392 /// assert!(!heap.is_empty());
1393 ///
1394 /// for x in heap.drain() {
1395 /// println!("{x}");
1396 /// }
1397 ///
1398 /// assert!(heap.is_empty());
1399 /// ```
1400 #[inline]
1401 #[stable(feature = "drain", since = "1.6.0")]
1402 pub fn drain(&mut self) -> Drain<'_, T, A> {
1403 Drain { iter: self.data.drain(..) }
1404 }
1405
1406 /// Drops all items from the binary heap.
1407 ///
1408 /// # Examples
1409 ///
1410 /// Basic usage:
1411 ///
1412 /// ```
1413 /// use std::collections::BinaryHeap;
1414 /// let mut heap = BinaryHeap::from([1, 3]);
1415 ///
1416 /// assert!(!heap.is_empty());
1417 ///
1418 /// heap.clear();
1419 ///
1420 /// assert!(heap.is_empty());
1421 /// ```
1422 #[stable(feature = "rust1", since = "1.0.0")]
1423 pub fn clear(&mut self) {
1424 self.drain();
1425 }
1426}
1427
1428/// Hole represents a hole in a slice i.e., an index without valid value
1429/// (because it was moved from or duplicated).
1430/// In drop, `Hole` will restore the slice by filling the hole
1431/// position with the value that was originally removed.
1432struct Hole<'a, T: 'a> {
1433 data: &'a mut [T],
1434 elt: ManuallyDrop<T>,
1435 pos: usize,
1436}
1437
1438impl<'a, T> Hole<'a, T> {
1439 /// Creates a new `Hole` at index `pos`.
1440 ///
1441 /// Unsafe because pos must be within the data slice.
1442 #[inline]
1443 unsafe fn new(data: &'a mut [T], pos: usize) -> Self {
1444 debug_assert!(pos < data.len());
1445 // SAFE: pos should be inside the slice
1446 let elt = unsafe { ptr::read(data.get_unchecked(pos)) };
1447 Hole { data, elt: ManuallyDrop::new(elt), pos }
1448 }
1449
1450 #[inline]
1451 fn pos(&self) -> usize {
1452 self.pos
1453 }
1454
1455 /// Returns a reference to the element removed.
1456 #[inline]
1457 fn element(&self) -> &T {
1458 &self.elt
1459 }
1460
1461 /// Returns a reference to the element at `index`.
1462 ///
1463 /// Unsafe because index must be within the data slice and not equal to pos.
1464 #[inline]
1465 unsafe fn get(&self, index: usize) -> &T {
1466 debug_assert!(index != self.pos);
1467 debug_assert!(index < self.data.len());
1468 unsafe { self.data.get_unchecked(index) }
1469 }
1470
1471 /// Move hole to new location
1472 ///
1473 /// Unsafe because index must be within the data slice and not equal to pos.
1474 #[inline]
1475 unsafe fn move_to(&mut self, index: usize) {
1476 debug_assert!(index != self.pos);
1477 debug_assert!(index < self.data.len());
1478 unsafe {
1479 let ptr = self.data.as_mut_ptr();
1480 let index_ptr: *const _ = ptr.add(index);
1481 let hole_ptr = ptr.add(self.pos);
1482 ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1);
1483 }
1484 self.pos = index;
1485 }
1486}
1487
1488impl<T> Drop for Hole<'_, T> {
1489 #[inline]
1490 fn drop(&mut self) {
1491 // fill the hole again
1492 unsafe {
1493 let pos: usize = self.pos;
1494 ptr::copy_nonoverlapping(&*self.elt, self.data.get_unchecked_mut(pos), count:1);
1495 }
1496 }
1497}
1498
1499/// An iterator over the elements of a `BinaryHeap`.
1500///
1501/// This `struct` is created by [`BinaryHeap::iter()`]. See its
1502/// documentation for more.
1503///
1504/// [`iter`]: BinaryHeap::iter
1505#[must_use = "iterators are lazy and do nothing unless consumed"]
1506#[stable(feature = "rust1", since = "1.0.0")]
1507pub struct Iter<'a, T: 'a> {
1508 iter: slice::Iter<'a, T>,
1509}
1510
1511#[stable(feature = "default_iters_sequel", since = "1.82.0")]
1512impl<T> Default for Iter<'_, T> {
1513 /// Creates an empty `binary_heap::Iter`.
1514 ///
1515 /// ```
1516 /// # use std::collections::binary_heap;
1517 /// let iter: binary_heap::Iter<'_, u8> = Default::default();
1518 /// assert_eq!(iter.len(), 0);
1519 /// ```
1520 fn default() -> Self {
1521 Iter { iter: Default::default() }
1522 }
1523}
1524
1525#[stable(feature = "collection_debug", since = "1.17.0")]
1526impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
1527 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1528 f.debug_tuple(name:"Iter").field(&self.iter.as_slice()).finish()
1529 }
1530}
1531
1532// FIXME(#26925) Remove in favor of `#[derive(Clone)]`
1533#[stable(feature = "rust1", since = "1.0.0")]
1534impl<T> Clone for Iter<'_, T> {
1535 fn clone(&self) -> Self {
1536 Iter { iter: self.iter.clone() }
1537 }
1538}
1539
1540#[stable(feature = "rust1", since = "1.0.0")]
1541impl<'a, T> Iterator for Iter<'a, T> {
1542 type Item = &'a T;
1543
1544 #[inline]
1545 fn next(&mut self) -> Option<&'a T> {
1546 self.iter.next()
1547 }
1548
1549 #[inline]
1550 fn size_hint(&self) -> (usize, Option<usize>) {
1551 self.iter.size_hint()
1552 }
1553
1554 #[inline]
1555 fn last(self) -> Option<&'a T> {
1556 self.iter.last()
1557 }
1558}
1559
1560#[stable(feature = "rust1", since = "1.0.0")]
1561impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
1562 #[inline]
1563 fn next_back(&mut self) -> Option<&'a T> {
1564 self.iter.next_back()
1565 }
1566}
1567
1568#[stable(feature = "rust1", since = "1.0.0")]
1569impl<T> ExactSizeIterator for Iter<'_, T> {
1570 fn is_empty(&self) -> bool {
1571 self.iter.is_empty()
1572 }
1573}
1574
1575#[stable(feature = "fused", since = "1.26.0")]
1576impl<T> FusedIterator for Iter<'_, T> {}
1577
1578/// An owning iterator over the elements of a `BinaryHeap`.
1579///
1580/// This `struct` is created by [`BinaryHeap::into_iter()`]
1581/// (provided by the [`IntoIterator`] trait). See its documentation for more.
1582///
1583/// [`into_iter`]: BinaryHeap::into_iter
1584#[stable(feature = "rust1", since = "1.0.0")]
1585#[derive(Clone)]
1586pub struct IntoIter<
1587 T,
1588 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
1589> {
1590 iter: vec::IntoIter<T, A>,
1591}
1592
1593impl<T, A: Allocator> IntoIter<T, A> {
1594 /// Returns a reference to the underlying allocator.
1595 #[unstable(feature = "allocator_api", issue = "32838")]
1596 pub fn allocator(&self) -> &A {
1597 self.iter.allocator()
1598 }
1599}
1600
1601#[stable(feature = "collection_debug", since = "1.17.0")]
1602impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
1603 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1604 f.debug_tuple(name:"IntoIter").field(&self.iter.as_slice()).finish()
1605 }
1606}
1607
1608#[stable(feature = "rust1", since = "1.0.0")]
1609impl<T, A: Allocator> Iterator for IntoIter<T, A> {
1610 type Item = T;
1611
1612 #[inline]
1613 fn next(&mut self) -> Option<T> {
1614 self.iter.next()
1615 }
1616
1617 #[inline]
1618 fn size_hint(&self) -> (usize, Option<usize>) {
1619 self.iter.size_hint()
1620 }
1621}
1622
1623#[stable(feature = "rust1", since = "1.0.0")]
1624impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
1625 #[inline]
1626 fn next_back(&mut self) -> Option<T> {
1627 self.iter.next_back()
1628 }
1629}
1630
1631#[stable(feature = "rust1", since = "1.0.0")]
1632impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
1633 fn is_empty(&self) -> bool {
1634 self.iter.is_empty()
1635 }
1636}
1637
1638#[stable(feature = "fused", since = "1.26.0")]
1639impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
1640
1641#[doc(hidden)]
1642#[unstable(issue = "none", feature = "trusted_fused")]
1643unsafe impl<T, A: Allocator> TrustedFused for IntoIter<T, A> {}
1644
1645#[stable(feature = "default_iters", since = "1.70.0")]
1646impl<T> Default for IntoIter<T> {
1647 /// Creates an empty `binary_heap::IntoIter`.
1648 ///
1649 /// ```
1650 /// # use std::collections::binary_heap;
1651 /// let iter: binary_heap::IntoIter<u8> = Default::default();
1652 /// assert_eq!(iter.len(), 0);
1653 /// ```
1654 fn default() -> Self {
1655 IntoIter { iter: Default::default() }
1656 }
1657}
1658
1659// In addition to the SAFETY invariants of the following three unsafe traits
1660// also refer to the vec::in_place_collect module documentation to get an overview
1661#[unstable(issue = "none", feature = "inplace_iteration")]
1662#[doc(hidden)]
1663unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
1664 type Source = IntoIter<T, A>;
1665
1666 #[inline]
1667 unsafe fn as_inner(&mut self) -> &mut Self::Source {
1668 self
1669 }
1670}
1671
1672#[unstable(issue = "none", feature = "inplace_iteration")]
1673#[doc(hidden)]
1674unsafe impl<I, A: Allocator> InPlaceIterable for IntoIter<I, A> {
1675 const EXPAND_BY: Option<NonZero<usize>> = NonZero::new(1);
1676 const MERGE_BY: Option<NonZero<usize>> = NonZero::new(1);
1677}
1678
1679#[cfg(not(test))]
1680unsafe impl<I> AsVecIntoIter for IntoIter<I> {
1681 type Item = I;
1682
1683 fn as_into_iter(&mut self) -> &mut vec::IntoIter<Self::Item> {
1684 &mut self.iter
1685 }
1686}
1687
1688#[must_use = "iterators are lazy and do nothing unless consumed"]
1689#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
1690#[derive(Clone, Debug)]
1691pub struct IntoIterSorted<
1692 T,
1693 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
1694> {
1695 inner: BinaryHeap<T, A>,
1696}
1697
1698impl<T, A: Allocator> IntoIterSorted<T, A> {
1699 /// Returns a reference to the underlying allocator.
1700 #[unstable(feature = "allocator_api", issue = "32838")]
1701 pub fn allocator(&self) -> &A {
1702 self.inner.allocator()
1703 }
1704}
1705
1706#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
1707impl<T: Ord, A: Allocator> Iterator for IntoIterSorted<T, A> {
1708 type Item = T;
1709
1710 #[inline]
1711 fn next(&mut self) -> Option<T> {
1712 self.inner.pop()
1713 }
1714
1715 #[inline]
1716 fn size_hint(&self) -> (usize, Option<usize>) {
1717 let exact: usize = self.inner.len();
1718 (exact, Some(exact))
1719 }
1720}
1721
1722#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
1723impl<T: Ord, A: Allocator> ExactSizeIterator for IntoIterSorted<T, A> {}
1724
1725#[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")]
1726impl<T: Ord, A: Allocator> FusedIterator for IntoIterSorted<T, A> {}
1727
1728#[unstable(feature = "trusted_len", issue = "37572")]
1729unsafe impl<T: Ord, A: Allocator> TrustedLen for IntoIterSorted<T, A> {}
1730
1731/// A draining iterator over the elements of a `BinaryHeap`.
1732///
1733/// This `struct` is created by [`BinaryHeap::drain()`]. See its
1734/// documentation for more.
1735///
1736/// [`drain`]: BinaryHeap::drain
1737#[stable(feature = "drain", since = "1.6.0")]
1738#[derive(Debug)]
1739pub struct Drain<
1740 'a,
1741 T: 'a,
1742 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
1743> {
1744 iter: vec::Drain<'a, T, A>,
1745}
1746
1747impl<T, A: Allocator> Drain<'_, T, A> {
1748 /// Returns a reference to the underlying allocator.
1749 #[unstable(feature = "allocator_api", issue = "32838")]
1750 pub fn allocator(&self) -> &A {
1751 self.iter.allocator()
1752 }
1753}
1754
1755#[stable(feature = "drain", since = "1.6.0")]
1756impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
1757 type Item = T;
1758
1759 #[inline]
1760 fn next(&mut self) -> Option<T> {
1761 self.iter.next()
1762 }
1763
1764 #[inline]
1765 fn size_hint(&self) -> (usize, Option<usize>) {
1766 self.iter.size_hint()
1767 }
1768}
1769
1770#[stable(feature = "drain", since = "1.6.0")]
1771impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> {
1772 #[inline]
1773 fn next_back(&mut self) -> Option<T> {
1774 self.iter.next_back()
1775 }
1776}
1777
1778#[stable(feature = "drain", since = "1.6.0")]
1779impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
1780 fn is_empty(&self) -> bool {
1781 self.iter.is_empty()
1782 }
1783}
1784
1785#[stable(feature = "fused", since = "1.26.0")]
1786impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}
1787
1788/// A draining iterator over the elements of a `BinaryHeap`.
1789///
1790/// This `struct` is created by [`BinaryHeap::drain_sorted()`]. See its
1791/// documentation for more.
1792///
1793/// [`drain_sorted`]: BinaryHeap::drain_sorted
1794#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
1795#[derive(Debug)]
1796pub struct DrainSorted<
1797 'a,
1798 T: Ord,
1799 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
1800> {
1801 inner: &'a mut BinaryHeap<T, A>,
1802}
1803
1804impl<'a, T: Ord, A: Allocator> DrainSorted<'a, T, A> {
1805 /// Returns a reference to the underlying allocator.
1806 #[unstable(feature = "allocator_api", issue = "32838")]
1807 pub fn allocator(&self) -> &A {
1808 self.inner.allocator()
1809 }
1810}
1811
1812#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
1813impl<'a, T: Ord, A: Allocator> Drop for DrainSorted<'a, T, A> {
1814 /// Removes heap elements in heap order.
1815 fn drop(&mut self) {
1816 struct DropGuard<'r, 'a, T: Ord, A: Allocator>(&'r mut DrainSorted<'a, T, A>);
1817
1818 impl<'r, 'a, T: Ord, A: Allocator> Drop for DropGuard<'r, 'a, T, A> {
1819 fn drop(&mut self) {
1820 while self.0.inner.pop().is_some() {}
1821 }
1822 }
1823
1824 while let Some(item: T) = self.inner.pop() {
1825 let guard: DropGuard<'_, '_, T, A> = DropGuard(self);
1826 drop(item);
1827 mem::forget(guard);
1828 }
1829 }
1830}
1831
1832#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
1833impl<T: Ord, A: Allocator> Iterator for DrainSorted<'_, T, A> {
1834 type Item = T;
1835
1836 #[inline]
1837 fn next(&mut self) -> Option<T> {
1838 self.inner.pop()
1839 }
1840
1841 #[inline]
1842 fn size_hint(&self) -> (usize, Option<usize>) {
1843 let exact: usize = self.inner.len();
1844 (exact, Some(exact))
1845 }
1846}
1847
1848#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
1849impl<T: Ord, A: Allocator> ExactSizeIterator for DrainSorted<'_, T, A> {}
1850
1851#[unstable(feature = "binary_heap_drain_sorted", issue = "59278")]
1852impl<T: Ord, A: Allocator> FusedIterator for DrainSorted<'_, T, A> {}
1853
1854#[unstable(feature = "trusted_len", issue = "37572")]
1855unsafe impl<T: Ord, A: Allocator> TrustedLen for DrainSorted<'_, T, A> {}
1856
1857#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
1858impl<T: Ord, A: Allocator> From<Vec<T, A>> for BinaryHeap<T, A> {
1859 /// Converts a `Vec<T>` into a `BinaryHeap<T>`.
1860 ///
1861 /// This conversion happens in-place, and has *O*(*n*) time complexity.
1862 fn from(vec: Vec<T, A>) -> BinaryHeap<T, A> {
1863 let mut heap: BinaryHeap = BinaryHeap { data: vec };
1864 heap.rebuild();
1865 heap
1866 }
1867}
1868
1869#[stable(feature = "std_collections_from_array", since = "1.56.0")]
1870impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T> {
1871 /// ```
1872 /// use std::collections::BinaryHeap;
1873 ///
1874 /// let mut h1 = BinaryHeap::from([1, 4, 2, 3]);
1875 /// let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into();
1876 /// while let Some((a, b)) = h1.pop().zip(h2.pop()) {
1877 /// assert_eq!(a, b);
1878 /// }
1879 /// ```
1880 fn from(arr: [T; N]) -> Self {
1881 Self::from_iter(arr)
1882 }
1883}
1884
1885#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
1886impl<T, A: Allocator> From<BinaryHeap<T, A>> for Vec<T, A> {
1887 /// Converts a `BinaryHeap<T>` into a `Vec<T>`.
1888 ///
1889 /// This conversion requires no data movement or allocation, and has
1890 /// constant time complexity.
1891 fn from(heap: BinaryHeap<T, A>) -> Vec<T, A> {
1892 heap.data
1893 }
1894}
1895
1896#[stable(feature = "rust1", since = "1.0.0")]
1897impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
1898 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> {
1899 BinaryHeap::from(iter.into_iter().collect::<Vec<_>>())
1900 }
1901}
1902
1903#[stable(feature = "rust1", since = "1.0.0")]
1904impl<T, A: Allocator> IntoIterator for BinaryHeap<T, A> {
1905 type Item = T;
1906 type IntoIter = IntoIter<T, A>;
1907
1908 /// Creates a consuming iterator, that is, one that moves each value out of
1909 /// the binary heap in arbitrary order. The binary heap cannot be used
1910 /// after calling this.
1911 ///
1912 /// # Examples
1913 ///
1914 /// Basic usage:
1915 ///
1916 /// ```
1917 /// use std::collections::BinaryHeap;
1918 /// let heap = BinaryHeap::from([1, 2, 3, 4]);
1919 ///
1920 /// // Print 1, 2, 3, 4 in arbitrary order
1921 /// for x in heap.into_iter() {
1922 /// // x has type i32, not &i32
1923 /// println!("{x}");
1924 /// }
1925 /// ```
1926 fn into_iter(self) -> IntoIter<T, A> {
1927 IntoIter { iter: self.data.into_iter() }
1928 }
1929}
1930
1931#[stable(feature = "rust1", since = "1.0.0")]
1932impl<'a, T, A: Allocator> IntoIterator for &'a BinaryHeap<T, A> {
1933 type Item = &'a T;
1934 type IntoIter = Iter<'a, T>;
1935
1936 fn into_iter(self) -> Iter<'a, T> {
1937 self.iter()
1938 }
1939}
1940
1941#[stable(feature = "rust1", since = "1.0.0")]
1942impl<T: Ord, A: Allocator> Extend<T> for BinaryHeap<T, A> {
1943 #[inline]
1944 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1945 let guard: RebuildOnDrop<'_, T, A> = RebuildOnDrop { rebuild_from: self.len(), heap: self };
1946 guard.heap.data.extend(iter);
1947 }
1948
1949 #[inline]
1950 fn extend_one(&mut self, item: T) {
1951 self.push(item);
1952 }
1953
1954 #[inline]
1955 fn extend_reserve(&mut self, additional: usize) {
1956 self.reserve(additional);
1957 }
1958}
1959
1960#[stable(feature = "extend_ref", since = "1.2.0")]
1961impl<'a, T: 'a + Ord + Copy, A: Allocator> Extend<&'a T> for BinaryHeap<T, A> {
1962 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1963 self.extend(iter.into_iter().cloned());
1964 }
1965
1966 #[inline]
1967 fn extend_one(&mut self, &item: T: &'a T) {
1968 self.push(item);
1969 }
1970
1971 #[inline]
1972 fn extend_reserve(&mut self, additional: usize) {
1973 self.reserve(additional);
1974 }
1975}
1976