1 // Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A priority queue implemented with a binary heap.
13 //! Insertion and popping the largest element have `O(log n)` time complexity.
14 //! Checking the largest element is `O(1)`. Converting a vector to a binary heap
15 //! can be done in-place, and has `O(n)` complexity. A binary heap can also be
16 //! converted to a sorted vector in-place, allowing it to be used for an `O(n
17 //! log n)` in-place heapsort.
21 //! This is a larger example that implements [Dijkstra's algorithm][dijkstra]
22 //! to solve the [shortest path problem][sssp] on a [directed graph][dir_graph].
23 //! It shows how to use `BinaryHeap` with custom types.
25 //! [dijkstra]: http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm
26 //! [sssp]: http://en.wikipedia.org/wiki/Shortest_path_problem
27 //! [dir_graph]: http://en.wikipedia.org/wiki/Directed_graph
30 //! use std::cmp::Ordering;
31 //! use std::collections::BinaryHeap;
34 //! #[derive(Copy, Clone, Eq, PartialEq)]
40 //! // The priority queue depends on `Ord`.
41 //! // Explicitly implement the trait so the queue becomes a min-heap
42 //! // instead of a max-heap.
43 //! impl Ord for State {
44 //! fn cmp(&self, other: &State) -> Ordering {
45 //! // Notice that the we flip the ordering here
46 //! other.cost.cmp(&self.cost)
50 //! // `PartialOrd` needs to be implemented as well.
51 //! impl PartialOrd for State {
52 //! fn partial_cmp(&self, other: &State) -> Option<Ordering> {
53 //! Some(self.cmp(other))
57 //! // Each node is represented as an `usize`, for a shorter implementation.
63 //! // Dijkstra's shortest path algorithm.
65 //! // Start at `start` and use `dist` to track the current shortest distance
66 //! // to each node. This implementation isn't memory-efficient as it may leave duplicate
67 //! // nodes in the queue. It also uses `usize::MAX` as a sentinel value,
68 //! // for a simpler implementation.
69 //! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> {
70 //! // dist[node] = current shortest distance from `start` to `node`
71 //! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect();
73 //! let mut heap = BinaryHeap::new();
75 //! // We're at `start`, with a zero cost
77 //! heap.push(State { cost: 0, position: start });
79 //! // Examine the frontier with lower cost nodes first (min-heap)
80 //! while let Some(State { cost, position }) = heap.pop() {
81 //! // Alternatively we could have continued to find all shortest paths
82 //! if position == goal { return Some(cost); }
84 //! // Important as we may have already found a better way
85 //! if cost > dist[position] { continue; }
87 //! // For each node we can reach, see if we can find a way with
88 //! // a lower cost going through this node
89 //! for edge in &adj_list[position] {
90 //! let next = State { cost: cost + edge.cost, position: edge.node };
92 //! // If so, add it to the frontier and continue
93 //! if next.cost < dist[next.position] {
95 //! // Relaxation, we have now found a better way
96 //! dist[next.position] = next.cost;
101 //! // Goal not reachable
106 //! // This is the directed graph we're going to use.
107 //! // The node numbers correspond to the different states,
108 //! // and the edge weights symbolize the cost of moving
109 //! // from one node to another.
110 //! // Note that the edges are one-way.
113 //! // +-----------------+
116 //! // 0 -----> 1 -----> 3 ---> 4
120 //! // +------> 2 -------+ |
122 //! // +---------------+
124 //! // The graph is represented as an adjacency list where each index,
125 //! // corresponding to a node value, has a list of outgoing edges.
126 //! // Chosen for its efficiency.
127 //! let graph = vec![
129 //! vec![Edge { node: 2, cost: 10 },
130 //! Edge { node: 1, cost: 1 }],
132 //! vec![Edge { node: 3, cost: 2 }],
134 //! vec![Edge { node: 1, cost: 1 },
135 //! Edge { node: 3, cost: 3 },
136 //! Edge { node: 4, cost: 1 }],
138 //! vec![Edge { node: 0, cost: 7 },
139 //! Edge { node: 4, cost: 2 }],
143 //! assert_eq!(shortest_path(&graph, 0, 1), Some(1));
144 //! assert_eq!(shortest_path(&graph, 0, 3), Some(3));
145 //! assert_eq!(shortest_path(&graph, 3, 0), Some(7));
146 //! assert_eq!(shortest_path(&graph, 0, 4), Some(5));
147 //! assert_eq!(shortest_path(&graph, 4, 0), None);
151 #![allow(missing_docs)]
152 #![stable(feature = "rust1", since = "1.0.0")]
154 use core::ops::{Deref, DerefMut};
155 use core::iter::{FromIterator, FusedIterator};
156 use core::mem::{swap, size_of};
161 use vec::{self, Vec};
163 use super::SpecExtend;
165 /// A priority queue implemented with a binary heap.
167 /// This will be a max-heap.
169 /// It is a logic error for an item to be modified in such a way that the
170 /// item's ordering relative to any other item, as determined by the `Ord`
171 /// trait, changes while it is in the heap. This is normally only possible
172 /// through `Cell`, `RefCell`, global state, I/O, or unsafe code.
177 /// use std::collections::BinaryHeap;
179 /// // Type inference lets us omit an explicit type signature (which
180 /// // would be `BinaryHeap<i32>` in this example).
181 /// let mut heap = BinaryHeap::new();
183 /// // We can use peek to look at the next item in the heap. In this case,
184 /// // there's no items in there yet so we get None.
185 /// assert_eq!(heap.peek(), None);
187 /// // Let's add some scores...
192 /// // Now peek shows the most important item in the heap.
193 /// assert_eq!(heap.peek(), Some(&5));
195 /// // We can check the length of a heap.
196 /// assert_eq!(heap.len(), 3);
198 /// // We can iterate over the items in the heap, although they are returned in
199 /// // a random order.
201 /// println!("{}", x);
204 /// // If we instead pop these scores, they should come back in order.
205 /// assert_eq!(heap.pop(), Some(5));
206 /// assert_eq!(heap.pop(), Some(2));
207 /// assert_eq!(heap.pop(), Some(1));
208 /// assert_eq!(heap.pop(), None);
210 /// // We can clear the heap of any remaining items.
213 /// // The heap should now be empty.
214 /// assert!(heap.is_empty())
216 #[stable(feature = "rust1", since = "1.0.0")]
217 pub struct BinaryHeap<T> {
221 /// A container object that represents the result of the [`peek_mut()`] method
222 /// on `BinaryHeap`. See its documentation for details.
224 /// [`peek_mut()`]: struct.BinaryHeap.html#method.peek_mut
225 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
226 pub struct PeekMut<'a, T: 'a + Ord> {
227 heap: &'a mut BinaryHeap<T>,
231 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
232 impl<'a, T: Ord> Drop for PeekMut<'a, T> {
235 self.heap.sift_down(0);
240 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
241 impl<'a, T: Ord> Deref for PeekMut<'a, T> {
243 fn deref(&self) -> &T {
248 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
249 impl<'a, T: Ord> DerefMut for PeekMut<'a, T> {
250 fn deref_mut(&mut self) -> &mut T {
251 &mut self.heap.data[0]
255 impl<'a, T: Ord> PeekMut<'a, T> {
256 /// Removes the peeked value from the heap and returns it.
257 #[unstable(feature = "binary_heap_peek_mut_pop", issue = "38863")]
258 pub fn pop(mut this: PeekMut<'a, T>) -> T {
259 let value = this.heap.pop().unwrap();
265 #[stable(feature = "rust1", since = "1.0.0")]
266 impl<T: Clone> Clone for BinaryHeap<T> {
267 fn clone(&self) -> Self {
268 BinaryHeap { data: self.data.clone() }
271 fn clone_from(&mut self, source: &Self) {
272 self.data.clone_from(&source.data);
276 #[stable(feature = "rust1", since = "1.0.0")]
277 impl<T: Ord> Default for BinaryHeap<T> {
278 /// Creates an empty `BinaryHeap<T>`.
280 fn default() -> BinaryHeap<T> {
285 #[stable(feature = "binaryheap_debug", since = "1.4.0")]
286 impl<T: fmt::Debug + Ord> fmt::Debug for BinaryHeap<T> {
287 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
288 f.debug_list().entries(self.iter()).finish()
292 impl<T: Ord> BinaryHeap<T> {
293 /// Creates an empty `BinaryHeap` as a max-heap.
300 /// use std::collections::BinaryHeap;
301 /// let mut heap = BinaryHeap::new();
304 #[stable(feature = "rust1", since = "1.0.0")]
305 pub fn new() -> BinaryHeap<T> {
306 BinaryHeap { data: vec![] }
309 /// Creates an empty `BinaryHeap` with a specific capacity.
310 /// This preallocates enough memory for `capacity` elements,
311 /// so that the `BinaryHeap` does not have to be reallocated
312 /// until it contains at least that many values.
319 /// use std::collections::BinaryHeap;
320 /// let mut heap = BinaryHeap::with_capacity(10);
323 #[stable(feature = "rust1", since = "1.0.0")]
324 pub fn with_capacity(capacity: usize) -> BinaryHeap<T> {
325 BinaryHeap { data: Vec::with_capacity(capacity) }
328 /// Returns an iterator visiting all values in the underlying vector, in
336 /// use std::collections::BinaryHeap;
337 /// let heap = BinaryHeap::from(vec![1, 2, 3, 4]);
339 /// // Print 1, 2, 3, 4 in arbitrary order
340 /// for x in heap.iter() {
341 /// println!("{}", x);
344 #[stable(feature = "rust1", since = "1.0.0")]
345 pub fn iter(&self) -> Iter<T> {
346 Iter { iter: self.data.iter() }
349 /// Returns the greatest item in the binary heap, or `None` if it is empty.
356 /// use std::collections::BinaryHeap;
357 /// let mut heap = BinaryHeap::new();
358 /// assert_eq!(heap.peek(), None);
363 /// assert_eq!(heap.peek(), Some(&5));
366 #[stable(feature = "rust1", since = "1.0.0")]
367 pub fn peek(&self) -> Option<&T> {
371 /// Returns a mutable reference to the greatest item in the binary heap, or
372 /// `None` if it is empty.
374 /// Note: If the `PeekMut` value is leaked, the heap may be in an
375 /// inconsistent state.
382 /// use std::collections::BinaryHeap;
383 /// let mut heap = BinaryHeap::new();
384 /// assert!(heap.peek_mut().is_none());
390 /// let mut val = heap.peek_mut().unwrap();
393 /// assert_eq!(heap.peek(), Some(&2));
395 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
396 pub fn peek_mut(&mut self) -> Option<PeekMut<T>> {
407 /// Returns the number of elements the binary heap can hold without reallocating.
414 /// use std::collections::BinaryHeap;
415 /// let mut heap = BinaryHeap::with_capacity(100);
416 /// assert!(heap.capacity() >= 100);
419 #[stable(feature = "rust1", since = "1.0.0")]
420 pub fn capacity(&self) -> usize {
424 /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the
425 /// given `BinaryHeap`. Does nothing if the capacity is already sufficient.
427 /// Note that the allocator may give the collection more space than it requests. Therefore
428 /// capacity can not be relied upon to be precisely minimal. Prefer `reserve` if future
429 /// insertions are expected.
433 /// Panics if the new capacity overflows `usize`.
440 /// use std::collections::BinaryHeap;
441 /// let mut heap = BinaryHeap::new();
442 /// heap.reserve_exact(100);
443 /// assert!(heap.capacity() >= 100);
446 #[stable(feature = "rust1", since = "1.0.0")]
447 pub fn reserve_exact(&mut self, additional: usize) {
448 self.data.reserve_exact(additional);
451 /// Reserves capacity for at least `additional` more elements to be inserted in the
452 /// `BinaryHeap`. The collection may reserve more space to avoid frequent reallocations.
456 /// Panics if the new capacity overflows `usize`.
463 /// use std::collections::BinaryHeap;
464 /// let mut heap = BinaryHeap::new();
465 /// heap.reserve(100);
466 /// assert!(heap.capacity() >= 100);
469 #[stable(feature = "rust1", since = "1.0.0")]
470 pub fn reserve(&mut self, additional: usize) {
471 self.data.reserve(additional);
474 /// Discards as much additional capacity as possible.
481 /// use std::collections::BinaryHeap;
482 /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100);
484 /// assert!(heap.capacity() >= 100);
485 /// heap.shrink_to_fit();
486 /// assert!(heap.capacity() == 0);
488 #[stable(feature = "rust1", since = "1.0.0")]
489 pub fn shrink_to_fit(&mut self) {
490 self.data.shrink_to_fit();
493 /// Removes the greatest item from the binary heap and returns it, or `None` if it
501 /// use std::collections::BinaryHeap;
502 /// let mut heap = BinaryHeap::from(vec![1, 3]);
504 /// assert_eq!(heap.pop(), Some(3));
505 /// assert_eq!(heap.pop(), Some(1));
506 /// assert_eq!(heap.pop(), None);
508 #[stable(feature = "rust1", since = "1.0.0")]
509 pub fn pop(&mut self) -> Option<T> {
510 self.data.pop().map(|mut item| {
511 if !self.is_empty() {
512 swap(&mut item, &mut self.data[0]);
513 self.sift_down_to_bottom(0);
519 /// Pushes an item onto the binary heap.
526 /// use std::collections::BinaryHeap;
527 /// let mut heap = BinaryHeap::new();
532 /// assert_eq!(heap.len(), 3);
533 /// assert_eq!(heap.peek(), Some(&5));
535 #[stable(feature = "rust1", since = "1.0.0")]
536 pub fn push(&mut self, item: T) {
537 let old_len = self.len();
538 self.data.push(item);
539 self.sift_up(0, old_len);
542 /// Pushes an item onto the binary heap, then pops the greatest item off the queue in
543 /// an optimized fashion.
550 /// #![feature(binary_heap_extras)]
551 /// #![allow(deprecated)]
553 /// use std::collections::BinaryHeap;
554 /// let mut heap = BinaryHeap::new();
558 /// assert_eq!(heap.push_pop(3), 5);
559 /// assert_eq!(heap.push_pop(9), 9);
560 /// assert_eq!(heap.len(), 2);
561 /// assert_eq!(heap.peek(), Some(&3));
563 #[unstable(feature = "binary_heap_extras",
564 reason = "needs to be audited",
566 #[rustc_deprecated(since = "1.13.0", reason = "use `peek_mut` instead")]
567 pub fn push_pop(&mut self, mut item: T) -> T {
568 match self.data.get_mut(0) {
572 swap(&mut item, top);
583 /// Pops the greatest item off the binary heap, then pushes an item onto the queue in
584 /// an optimized fashion. The push is done regardless of whether the binary heap
592 /// #![feature(binary_heap_extras)]
593 /// #![allow(deprecated)]
595 /// use std::collections::BinaryHeap;
596 /// let mut heap = BinaryHeap::new();
598 /// assert_eq!(heap.replace(1), None);
599 /// assert_eq!(heap.replace(3), Some(1));
600 /// assert_eq!(heap.len(), 1);
601 /// assert_eq!(heap.peek(), Some(&3));
603 #[unstable(feature = "binary_heap_extras",
604 reason = "needs to be audited",
606 #[rustc_deprecated(since = "1.13.0", reason = "use `peek_mut` instead")]
607 pub fn replace(&mut self, mut item: T) -> Option<T> {
608 if !self.is_empty() {
609 swap(&mut item, &mut self.data[0]);
618 /// Consumes the `BinaryHeap` and returns the underlying vector
619 /// in arbitrary order.
626 /// use std::collections::BinaryHeap;
627 /// let heap = BinaryHeap::from(vec![1, 2, 3, 4, 5, 6, 7]);
628 /// let vec = heap.into_vec();
630 /// // Will print in some order
632 /// println!("{}", x);
635 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
636 pub fn into_vec(self) -> Vec<T> {
640 /// Consumes the `BinaryHeap` and returns a vector in sorted
641 /// (ascending) order.
648 /// use std::collections::BinaryHeap;
650 /// let mut heap = BinaryHeap::from(vec![1, 2, 4, 5, 7]);
654 /// let vec = heap.into_sorted_vec();
655 /// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);
657 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
658 pub fn into_sorted_vec(mut self) -> Vec<T> {
659 let mut end = self.len();
662 self.data.swap(0, end);
663 self.sift_down_range(0, end);
668 // The implementations of sift_up and sift_down use unsafe blocks in
669 // order to move an element out of the vector (leaving behind a
670 // hole), shift along the others and move the removed element back into the
671 // vector at the final location of the hole.
672 // The `Hole` type is used to represent this, and make sure
673 // the hole is filled back at the end of its scope, even on panic.
674 // Using a hole reduces the constant factor compared to using swaps,
675 // which involves twice as many moves.
676 fn sift_up(&mut self, start: usize, pos: usize) {
678 // Take out the value at `pos` and create a hole.
679 let mut hole = Hole::new(&mut self.data, pos);
681 while hole.pos() > start {
682 let parent = (hole.pos() - 1) / 2;
683 if hole.element() <= hole.get(parent) {
686 hole.move_to(parent);
691 /// Take an element at `pos` and move it down the heap,
692 /// while its children are larger.
693 fn sift_down_range(&mut self, pos: usize, end: usize) {
695 let mut hole = Hole::new(&mut self.data, pos);
696 let mut child = 2 * pos + 1;
698 let right = child + 1;
699 // compare with the greater of the two children
700 if right < end && !(hole.get(child) > hole.get(right)) {
703 // if we are already in order, stop.
704 if hole.element() >= hole.get(child) {
708 child = 2 * hole.pos() + 1;
713 fn sift_down(&mut self, pos: usize) {
714 let len = self.len();
715 self.sift_down_range(pos, len);
718 /// Take an element at `pos` and move it all the way down the heap,
719 /// then sift it up to its position.
721 /// Note: This is faster when the element is known to be large / should
722 /// be closer to the bottom.
723 fn sift_down_to_bottom(&mut self, mut pos: usize) {
724 let end = self.len();
727 let mut hole = Hole::new(&mut self.data, pos);
728 let mut child = 2 * pos + 1;
730 let right = child + 1;
731 // compare with the greater of the two children
732 if right < end && !(hole.get(child) > hole.get(right)) {
736 child = 2 * hole.pos() + 1;
740 self.sift_up(start, pos);
743 /// Returns the length of the binary heap.
750 /// use std::collections::BinaryHeap;
751 /// let heap = BinaryHeap::from(vec![1, 3]);
753 /// assert_eq!(heap.len(), 2);
755 #[stable(feature = "rust1", since = "1.0.0")]
756 pub fn len(&self) -> usize {
760 /// Checks if the binary heap is empty.
767 /// use std::collections::BinaryHeap;
768 /// let mut heap = BinaryHeap::new();
770 /// assert!(heap.is_empty());
776 /// assert!(!heap.is_empty());
778 #[stable(feature = "rust1", since = "1.0.0")]
779 pub fn is_empty(&self) -> bool {
783 /// Clears the binary heap, returning an iterator over the removed elements.
785 /// The elements are removed in arbitrary order.
792 /// use std::collections::BinaryHeap;
793 /// let mut heap = BinaryHeap::from(vec![1, 3]);
795 /// assert!(!heap.is_empty());
797 /// for x in heap.drain() {
798 /// println!("{}", x);
801 /// assert!(heap.is_empty());
804 #[stable(feature = "drain", since = "1.6.0")]
805 pub fn drain(&mut self) -> Drain<T> {
806 Drain { iter: self.data.drain(..) }
809 /// Drops all items from the binary heap.
816 /// use std::collections::BinaryHeap;
817 /// let mut heap = BinaryHeap::from(vec![1, 3]);
819 /// assert!(!heap.is_empty());
823 /// assert!(heap.is_empty());
825 #[stable(feature = "rust1", since = "1.0.0")]
826 pub fn clear(&mut self) {
830 fn rebuild(&mut self) {
831 let mut n = self.len() / 2;
838 /// Moves all the elements of `other` into `self`, leaving `other` empty.
845 /// use std::collections::BinaryHeap;
847 /// let v = vec![-10, 1, 2, 3, 3];
848 /// let mut a = BinaryHeap::from(v);
850 /// let v = vec![-20, 5, 43];
851 /// let mut b = BinaryHeap::from(v);
853 /// a.append(&mut b);
855 /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
856 /// assert!(b.is_empty());
858 #[stable(feature = "binary_heap_append", since = "1.11.0")]
859 pub fn append(&mut self, other: &mut Self) {
860 if self.len() < other.len() {
864 if other.is_empty() {
869 fn log2_fast(x: usize) -> usize {
870 8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1
873 // `rebuild` takes O(len1 + len2) operations
874 // and about 2 * (len1 + len2) comparisons in the worst case
875 // while `extend` takes O(len2 * log_2(len1)) operations
876 // and about 1 * len2 * log_2(len1) comparisons in the worst case,
877 // assuming len1 >= len2.
879 fn better_to_rebuild(len1: usize, len2: usize) -> bool {
880 2 * (len1 + len2) < len2 * log2_fast(len1)
883 if better_to_rebuild(self.len(), other.len()) {
884 self.data.append(&mut other.data);
887 self.extend(other.drain());
892 /// Hole represents a hole in a slice i.e. an index without valid value
893 /// (because it was moved from or duplicated).
894 /// In drop, `Hole` will restore the slice by filling the hole
895 /// position with the value that was originally removed.
896 struct Hole<'a, T: 'a> {
898 /// `elt` is always `Some` from new until drop.
903 impl<'a, T> Hole<'a, T> {
904 /// Create a new Hole at index `pos`.
906 /// Unsafe because pos must be within the data slice.
908 unsafe fn new(data: &'a mut [T], pos: usize) -> Self {
909 debug_assert!(pos < data.len());
910 let elt = ptr::read(&data[pos]);
919 fn pos(&self) -> usize {
923 /// Return a reference to the element removed
925 fn element(&self) -> &T {
926 self.elt.as_ref().unwrap()
929 /// Return a reference to the element at `index`.
931 /// Unsafe because index must be within the data slice and not equal to pos.
933 unsafe fn get(&self, index: usize) -> &T {
934 debug_assert!(index != self.pos);
935 debug_assert!(index < self.data.len());
936 self.data.get_unchecked(index)
939 /// Move hole to new location
941 /// Unsafe because index must be within the data slice and not equal to pos.
943 unsafe fn move_to(&mut self, index: usize) {
944 debug_assert!(index != self.pos);
945 debug_assert!(index < self.data.len());
946 let index_ptr: *const _ = self.data.get_unchecked(index);
947 let hole_ptr = self.data.get_unchecked_mut(self.pos);
948 ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1);
953 impl<'a, T> Drop for Hole<'a, T> {
956 // fill the hole again
959 ptr::write(self.data.get_unchecked_mut(pos), self.elt.take().unwrap());
964 /// `BinaryHeap` iterator.
965 #[stable(feature = "rust1", since = "1.0.0")]
966 pub struct Iter<'a, T: 'a> {
967 iter: slice::Iter<'a, T>,
970 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
971 #[stable(feature = "rust1", since = "1.0.0")]
972 impl<'a, T> Clone for Iter<'a, T> {
973 fn clone(&self) -> Iter<'a, T> {
974 Iter { iter: self.iter.clone() }
978 #[stable(feature = "rust1", since = "1.0.0")]
979 impl<'a, T> Iterator for Iter<'a, T> {
983 fn next(&mut self) -> Option<&'a T> {
988 fn size_hint(&self) -> (usize, Option<usize>) {
989 self.iter.size_hint()
993 #[stable(feature = "rust1", since = "1.0.0")]
994 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
996 fn next_back(&mut self) -> Option<&'a T> {
997 self.iter.next_back()
1001 #[stable(feature = "rust1", since = "1.0.0")]
1002 impl<'a, T> ExactSizeIterator for Iter<'a, T> {
1003 fn is_empty(&self) -> bool {
1004 self.iter.is_empty()
1008 #[unstable(feature = "fused", issue = "35602")]
1009 impl<'a, T> FusedIterator for Iter<'a, T> {}
1011 /// An iterator that moves out of a `BinaryHeap`.
1012 #[stable(feature = "rust1", since = "1.0.0")]
1014 pub struct IntoIter<T> {
1015 iter: vec::IntoIter<T>,
1018 #[stable(feature = "rust1", since = "1.0.0")]
1019 impl<T> Iterator for IntoIter<T> {
1023 fn next(&mut self) -> Option<T> {
1028 fn size_hint(&self) -> (usize, Option<usize>) {
1029 self.iter.size_hint()
1033 #[stable(feature = "rust1", since = "1.0.0")]
1034 impl<T> DoubleEndedIterator for IntoIter<T> {
1036 fn next_back(&mut self) -> Option<T> {
1037 self.iter.next_back()
1041 #[stable(feature = "rust1", since = "1.0.0")]
1042 impl<T> ExactSizeIterator for IntoIter<T> {
1043 fn is_empty(&self) -> bool {
1044 self.iter.is_empty()
1048 #[unstable(feature = "fused", issue = "35602")]
1049 impl<T> FusedIterator for IntoIter<T> {}
1051 /// An iterator that drains a `BinaryHeap`.
1052 #[stable(feature = "drain", since = "1.6.0")]
1053 pub struct Drain<'a, T: 'a> {
1054 iter: vec::Drain<'a, T>,
1057 #[stable(feature = "drain", since = "1.6.0")]
1058 impl<'a, T: 'a> Iterator for Drain<'a, T> {
1062 fn next(&mut self) -> Option<T> {
1067 fn size_hint(&self) -> (usize, Option<usize>) {
1068 self.iter.size_hint()
1072 #[stable(feature = "drain", since = "1.6.0")]
1073 impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
1075 fn next_back(&mut self) -> Option<T> {
1076 self.iter.next_back()
1080 #[stable(feature = "drain", since = "1.6.0")]
1081 impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {
1082 fn is_empty(&self) -> bool {
1083 self.iter.is_empty()
1087 #[unstable(feature = "fused", issue = "35602")]
1088 impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}
1090 #[stable(feature = "rust1", since = "1.0.0")]
1091 impl<T: Ord> From<Vec<T>> for BinaryHeap<T> {
1092 fn from(vec: Vec<T>) -> BinaryHeap<T> {
1093 let mut heap = BinaryHeap { data: vec };
1099 #[stable(feature = "rust1", since = "1.0.0")]
1100 impl<T> From<BinaryHeap<T>> for Vec<T> {
1101 fn from(heap: BinaryHeap<T>) -> Vec<T> {
1106 #[stable(feature = "rust1", since = "1.0.0")]
1107 impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
1108 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> {
1109 BinaryHeap::from(iter.into_iter().collect::<Vec<_>>())
1113 #[stable(feature = "rust1", since = "1.0.0")]
1114 impl<T: Ord> IntoIterator for BinaryHeap<T> {
1116 type IntoIter = IntoIter<T>;
1118 /// Creates a consuming iterator, that is, one that moves each value out of
1119 /// the binary heap in arbitrary order. The binary heap cannot be used
1120 /// after calling this.
1127 /// use std::collections::BinaryHeap;
1128 /// let heap = BinaryHeap::from(vec![1, 2, 3, 4]);
1130 /// // Print 1, 2, 3, 4 in arbitrary order
1131 /// for x in heap.into_iter() {
1132 /// // x has type i32, not &i32
1133 /// println!("{}", x);
1136 fn into_iter(self) -> IntoIter<T> {
1137 IntoIter { iter: self.data.into_iter() }
1141 #[stable(feature = "rust1", since = "1.0.0")]
1142 impl<'a, T> IntoIterator for &'a BinaryHeap<T>
1146 type IntoIter = Iter<'a, T>;
1148 fn into_iter(self) -> Iter<'a, T> {
1153 #[stable(feature = "rust1", since = "1.0.0")]
1154 impl<T: Ord> Extend<T> for BinaryHeap<T> {
1156 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1157 <Self as SpecExtend<I>>::spec_extend(self, iter);
1161 impl<T: Ord, I: IntoIterator<Item = T>> SpecExtend<I> for BinaryHeap<T> {
1162 default fn spec_extend(&mut self, iter: I) {
1163 self.extend_desugared(iter.into_iter());
1167 impl<T: Ord> SpecExtend<BinaryHeap<T>> for BinaryHeap<T> {
1168 fn spec_extend(&mut self, ref mut other: BinaryHeap<T>) {
1173 impl<T: Ord> BinaryHeap<T> {
1174 fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1175 let iterator = iter.into_iter();
1176 let (lower, _) = iterator.size_hint();
1178 self.reserve(lower);
1180 for elem in iterator {
1186 #[stable(feature = "extend_ref", since = "1.2.0")]
1187 impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BinaryHeap<T> {
1188 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1189 self.extend(iter.into_iter().cloned());