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, Place, Placer, InPlace};
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) -> 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);
692 /// Take an element at `pos` and move it down the heap,
693 /// while its children are larger.
694 fn sift_down_range(&mut self, pos: usize, end: usize) {
696 let mut hole = Hole::new(&mut self.data, pos);
697 let mut child = 2 * pos + 1;
699 let right = child + 1;
700 // compare with the greater of the two children
701 if right < end && !(hole.get(child) > hole.get(right)) {
704 // if we are already in order, stop.
705 if hole.element() >= hole.get(child) {
709 child = 2 * hole.pos() + 1;
714 fn sift_down(&mut self, pos: usize) {
715 let len = self.len();
716 self.sift_down_range(pos, len);
719 /// Take an element at `pos` and move it all the way down the heap,
720 /// then sift it up to its position.
722 /// Note: This is faster when the element is known to be large / should
723 /// be closer to the bottom.
724 fn sift_down_to_bottom(&mut self, mut pos: usize) {
725 let end = self.len();
728 let mut hole = Hole::new(&mut self.data, pos);
729 let mut child = 2 * pos + 1;
731 let right = child + 1;
732 // compare with the greater of the two children
733 if right < end && !(hole.get(child) > hole.get(right)) {
737 child = 2 * hole.pos() + 1;
741 self.sift_up(start, pos);
744 /// Returns the length of the binary heap.
751 /// use std::collections::BinaryHeap;
752 /// let heap = BinaryHeap::from(vec![1, 3]);
754 /// assert_eq!(heap.len(), 2);
756 #[stable(feature = "rust1", since = "1.0.0")]
757 pub fn len(&self) -> usize {
761 /// Checks if the binary heap is empty.
768 /// use std::collections::BinaryHeap;
769 /// let mut heap = BinaryHeap::new();
771 /// assert!(heap.is_empty());
777 /// assert!(!heap.is_empty());
779 #[stable(feature = "rust1", since = "1.0.0")]
780 pub fn is_empty(&self) -> bool {
784 /// Clears the binary heap, returning an iterator over the removed elements.
786 /// The elements are removed in arbitrary order.
793 /// use std::collections::BinaryHeap;
794 /// let mut heap = BinaryHeap::from(vec![1, 3]);
796 /// assert!(!heap.is_empty());
798 /// for x in heap.drain() {
799 /// println!("{}", x);
802 /// assert!(heap.is_empty());
805 #[stable(feature = "drain", since = "1.6.0")]
806 pub fn drain(&mut self) -> Drain<T> {
807 Drain { iter: self.data.drain(..) }
810 /// Drops all items from the binary heap.
817 /// use std::collections::BinaryHeap;
818 /// let mut heap = BinaryHeap::from(vec![1, 3]);
820 /// assert!(!heap.is_empty());
824 /// assert!(heap.is_empty());
826 #[stable(feature = "rust1", since = "1.0.0")]
827 pub fn clear(&mut self) {
831 fn rebuild(&mut self) {
832 let mut n = self.len() / 2;
839 /// Moves all the elements of `other` into `self`, leaving `other` empty.
846 /// use std::collections::BinaryHeap;
848 /// let v = vec![-10, 1, 2, 3, 3];
849 /// let mut a = BinaryHeap::from(v);
851 /// let v = vec![-20, 5, 43];
852 /// let mut b = BinaryHeap::from(v);
854 /// a.append(&mut b);
856 /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]);
857 /// assert!(b.is_empty());
859 #[stable(feature = "binary_heap_append", since = "1.11.0")]
860 pub fn append(&mut self, other: &mut Self) {
861 if self.len() < other.len() {
865 if other.is_empty() {
870 fn log2_fast(x: usize) -> usize {
871 8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1
874 // `rebuild` takes O(len1 + len2) operations
875 // and about 2 * (len1 + len2) comparisons in the worst case
876 // while `extend` takes O(len2 * log_2(len1)) operations
877 // and about 1 * len2 * log_2(len1) comparisons in the worst case,
878 // assuming len1 >= len2.
880 fn better_to_rebuild(len1: usize, len2: usize) -> bool {
881 2 * (len1 + len2) < len2 * log2_fast(len1)
884 if better_to_rebuild(self.len(), other.len()) {
885 self.data.append(&mut other.data);
888 self.extend(other.drain());
893 /// Hole represents a hole in a slice i.e. an index without valid value
894 /// (because it was moved from or duplicated).
895 /// In drop, `Hole` will restore the slice by filling the hole
896 /// position with the value that was originally removed.
897 struct Hole<'a, T: 'a> {
899 /// `elt` is always `Some` from new until drop.
904 impl<'a, T> Hole<'a, T> {
905 /// Create a new Hole at index `pos`.
907 /// Unsafe because pos must be within the data slice.
909 unsafe fn new(data: &'a mut [T], pos: usize) -> Self {
910 debug_assert!(pos < data.len());
911 let elt = ptr::read(&data[pos]);
920 fn pos(&self) -> usize {
924 /// Return a reference to the element removed
926 fn element(&self) -> &T {
927 self.elt.as_ref().unwrap()
930 /// Return a reference to the element at `index`.
932 /// Unsafe because index must be within the data slice and not equal to pos.
934 unsafe fn get(&self, index: usize) -> &T {
935 debug_assert!(index != self.pos);
936 debug_assert!(index < self.data.len());
937 self.data.get_unchecked(index)
940 /// Move hole to new location
942 /// Unsafe because index must be within the data slice and not equal to pos.
944 unsafe fn move_to(&mut self, index: usize) {
945 debug_assert!(index != self.pos);
946 debug_assert!(index < self.data.len());
947 let index_ptr: *const _ = self.data.get_unchecked(index);
948 let hole_ptr = self.data.get_unchecked_mut(self.pos);
949 ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1);
954 impl<'a, T> Drop for Hole<'a, T> {
957 // fill the hole again
960 ptr::write(self.data.get_unchecked_mut(pos), self.elt.take().unwrap());
965 /// `BinaryHeap` iterator.
966 #[stable(feature = "rust1", since = "1.0.0")]
967 pub struct Iter<'a, T: 'a> {
968 iter: slice::Iter<'a, T>,
971 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
972 #[stable(feature = "rust1", since = "1.0.0")]
973 impl<'a, T> Clone for Iter<'a, T> {
974 fn clone(&self) -> Iter<'a, T> {
975 Iter { iter: self.iter.clone() }
979 #[stable(feature = "rust1", since = "1.0.0")]
980 impl<'a, T> Iterator for Iter<'a, T> {
984 fn next(&mut self) -> Option<&'a T> {
989 fn size_hint(&self) -> (usize, Option<usize>) {
990 self.iter.size_hint()
994 #[stable(feature = "rust1", since = "1.0.0")]
995 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
997 fn next_back(&mut self) -> Option<&'a T> {
998 self.iter.next_back()
1002 #[stable(feature = "rust1", since = "1.0.0")]
1003 impl<'a, T> ExactSizeIterator for Iter<'a, T> {
1004 fn is_empty(&self) -> bool {
1005 self.iter.is_empty()
1009 #[unstable(feature = "fused", issue = "35602")]
1010 impl<'a, T> FusedIterator for Iter<'a, T> {}
1012 /// An iterator that moves out of a `BinaryHeap`.
1013 #[stable(feature = "rust1", since = "1.0.0")]
1015 pub struct IntoIter<T> {
1016 iter: vec::IntoIter<T>,
1019 #[stable(feature = "rust1", since = "1.0.0")]
1020 impl<T> Iterator for IntoIter<T> {
1024 fn next(&mut self) -> Option<T> {
1029 fn size_hint(&self) -> (usize, Option<usize>) {
1030 self.iter.size_hint()
1034 #[stable(feature = "rust1", since = "1.0.0")]
1035 impl<T> DoubleEndedIterator for IntoIter<T> {
1037 fn next_back(&mut self) -> Option<T> {
1038 self.iter.next_back()
1042 #[stable(feature = "rust1", since = "1.0.0")]
1043 impl<T> ExactSizeIterator for IntoIter<T> {
1044 fn is_empty(&self) -> bool {
1045 self.iter.is_empty()
1049 #[unstable(feature = "fused", issue = "35602")]
1050 impl<T> FusedIterator for IntoIter<T> {}
1052 /// An iterator that drains a `BinaryHeap`.
1053 #[stable(feature = "drain", since = "1.6.0")]
1054 pub struct Drain<'a, T: 'a> {
1055 iter: vec::Drain<'a, T>,
1058 #[stable(feature = "drain", since = "1.6.0")]
1059 impl<'a, T: 'a> Iterator for Drain<'a, T> {
1063 fn next(&mut self) -> Option<T> {
1068 fn size_hint(&self) -> (usize, Option<usize>) {
1069 self.iter.size_hint()
1073 #[stable(feature = "drain", since = "1.6.0")]
1074 impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
1076 fn next_back(&mut self) -> Option<T> {
1077 self.iter.next_back()
1081 #[stable(feature = "drain", since = "1.6.0")]
1082 impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {
1083 fn is_empty(&self) -> bool {
1084 self.iter.is_empty()
1088 #[unstable(feature = "fused", issue = "35602")]
1089 impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}
1091 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
1092 impl<T: Ord> From<Vec<T>> for BinaryHeap<T> {
1093 fn from(vec: Vec<T>) -> BinaryHeap<T> {
1094 let mut heap = BinaryHeap { data: vec };
1100 #[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
1101 impl<T> From<BinaryHeap<T>> for Vec<T> {
1102 fn from(heap: BinaryHeap<T>) -> Vec<T> {
1107 #[stable(feature = "rust1", since = "1.0.0")]
1108 impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
1109 fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> {
1110 BinaryHeap::from(iter.into_iter().collect::<Vec<_>>())
1114 #[stable(feature = "rust1", since = "1.0.0")]
1115 impl<T: Ord> IntoIterator for BinaryHeap<T> {
1117 type IntoIter = IntoIter<T>;
1119 /// Creates a consuming iterator, that is, one that moves each value out of
1120 /// the binary heap in arbitrary order. The binary heap cannot be used
1121 /// after calling this.
1128 /// use std::collections::BinaryHeap;
1129 /// let heap = BinaryHeap::from(vec![1, 2, 3, 4]);
1131 /// // Print 1, 2, 3, 4 in arbitrary order
1132 /// for x in heap.into_iter() {
1133 /// // x has type i32, not &i32
1134 /// println!("{}", x);
1137 fn into_iter(self) -> IntoIter<T> {
1138 IntoIter { iter: self.data.into_iter() }
1142 #[stable(feature = "rust1", since = "1.0.0")]
1143 impl<'a, T> IntoIterator for &'a BinaryHeap<T>
1147 type IntoIter = Iter<'a, T>;
1149 fn into_iter(self) -> Iter<'a, T> {
1154 #[stable(feature = "rust1", since = "1.0.0")]
1155 impl<T: Ord> Extend<T> for BinaryHeap<T> {
1157 fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1158 <Self as SpecExtend<I>>::spec_extend(self, iter);
1162 impl<T: Ord, I: IntoIterator<Item = T>> SpecExtend<I> for BinaryHeap<T> {
1163 default fn spec_extend(&mut self, iter: I) {
1164 self.extend_desugared(iter.into_iter());
1168 impl<T: Ord> SpecExtend<BinaryHeap<T>> for BinaryHeap<T> {
1169 fn spec_extend(&mut self, ref mut other: BinaryHeap<T>) {
1174 impl<T: Ord> BinaryHeap<T> {
1175 fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) {
1176 let iterator = iter.into_iter();
1177 let (lower, _) = iterator.size_hint();
1179 self.reserve(lower);
1181 for elem in iterator {
1187 #[stable(feature = "extend_ref", since = "1.2.0")]
1188 impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BinaryHeap<T> {
1189 fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
1190 self.extend(iter.into_iter().cloned());
1194 #[unstable(feature = "collection_placement",
1195 reason = "placement protocol is subject to change",
1197 pub struct BinaryHeapPlace<'a, T: 'a>
1198 where T: Clone + Ord {
1199 heap: *mut BinaryHeap<T>,
1200 place: vec::PlaceBack<'a, T>,
1203 #[unstable(feature = "collection_placement",
1204 reason = "placement protocol is subject to change",
1206 impl<'a, T: 'a> Placer<T> for &'a mut BinaryHeap<T>
1207 where T: Clone + Ord {
1208 type Place = BinaryHeapPlace<'a, T>;
1210 fn make_place(self) -> Self::Place {
1211 let ptr = self as *mut BinaryHeap<T>;
1212 let place = Placer::make_place(self.data.place_back());
1220 #[unstable(feature = "collection_placement",
1221 reason = "placement protocol is subject to change",
1223 impl<'a, T> Place<T> for BinaryHeapPlace<'a, T>
1224 where T: Clone + Ord {
1225 fn pointer(&mut self) -> *mut T {
1226 self.place.pointer()
1230 #[unstable(feature = "collection_placement",
1231 reason = "placement protocol is subject to change",
1233 impl<'a, T> InPlace<T> for BinaryHeapPlace<'a, T>
1234 where T: Clone + Ord {
1237 unsafe fn finalize(self) -> &'a T {
1238 self.place.finalize();
1240 let heap: &mut BinaryHeap<T> = &mut *self.heap;
1241 let len = heap.len();
1242 let i = heap.sift_up(0, len - 1);
1243 heap.data.get_unchecked(i)