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Commit | Line | Data |
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1a4d82fc JJ |
1 | //! A priority queue implemented with a binary heap. |
2 | //! | |
3dfed10e XL |
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 | |
c295e0f8 | 6 | //! converted to a sorted vector in-place, allowing it to be used for an *O*(*n* * log(*n*)) |
ba9703b0 | 7 | //! in-place heapsort. |
1a4d82fc JJ |
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]. | |
cc61c64b | 13 | //! It shows how to use [`BinaryHeap`] with custom types. |
1a4d82fc | 14 | //! |
3dfed10e XL |
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 | |
1a4d82fc JJ |
18 | //! |
19 | //! ``` | |
20 | //! use std::cmp::Ordering; | |
21 | //! use std::collections::BinaryHeap; | |
1a4d82fc | 22 | //! |
c34b1796 | 23 | //! #[derive(Copy, Clone, Eq, PartialEq)] |
1a4d82fc | 24 | //! struct State { |
85aaf69f SL |
25 | //! cost: usize, |
26 | //! position: usize, | |
1a4d82fc JJ |
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 { | |
1b1a35ee | 33 | //! fn cmp(&self, other: &Self) -> Ordering { |
7cac9316 XL |
34 | //! // Notice that the 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. | |
1a4d82fc | 37 | //! other.cost.cmp(&self.cost) |
7cac9316 | 38 | //! .then_with(|| self.position.cmp(&other.position)) |
1a4d82fc JJ |
39 | //! } |
40 | //! } | |
41 | //! | |
42 | //! // `PartialOrd` needs to be implemented as well. | |
43 | //! impl PartialOrd for State { | |
1b1a35ee | 44 | //! fn partial_cmp(&self, other: &Self) -> Option<Ordering> { |
1a4d82fc JJ |
45 | //! Some(self.cmp(other)) |
46 | //! } | |
47 | //! } | |
48 | //! | |
94222f64 | 49 | //! // Each node is represented as a `usize`, for a shorter implementation. |
1a4d82fc | 50 | //! struct Edge { |
85aaf69f SL |
51 | //! node: usize, |
52 | //! cost: usize, | |
1a4d82fc JJ |
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 | |
85aaf69f | 59 | //! // nodes in the queue. It also uses `usize::MAX` as a sentinel value, |
1a4d82fc | 60 | //! // for a simpler implementation. |
9cc50fc6 | 61 | //! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> { |
1a4d82fc | 62 | //! // dist[node] = current shortest distance from `start` to `node` |
85aaf69f | 63 | //! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect(); |
1a4d82fc JJ |
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 | |
9cc50fc6 | 74 | //! if position == goal { return Some(cost); } |
1a4d82fc JJ |
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 | |
62682a34 | 81 | //! for edge in &adj_list[position] { |
1a4d82fc JJ |
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 | |
9cc50fc6 | 94 | //! None |
1a4d82fc JJ |
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 | //! // | | | |
e9174d1e | 107 | //! // v 1 2 | 2 |
1a4d82fc JJ |
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 | //! | |
9cc50fc6 SL |
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); | |
1a4d82fc JJ |
140 | //! } |
141 | //! ``` | |
142 | ||
143 | #![allow(missing_docs)] | |
85aaf69f | 144 | #![stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 145 | |
fe692bf9 | 146 | use core::alloc::Allocator; |
dfeec247 | 147 | use core::fmt; |
353b0b11 | 148 | use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen}; |
1b1a35ee | 149 | use core::mem::{self, swap, ManuallyDrop}; |
9c376795 | 150 | use core::num::NonZeroUsize; |
dfeec247 | 151 | use core::ops::{Deref, DerefMut}; |
1a4d82fc JJ |
152 | use core::ptr; |
153 | ||
fe692bf9 | 154 | use crate::alloc::Global; |
a2a8927a | 155 | use crate::collections::TryReserveError; |
9fa01778 | 156 | use crate::slice; |
5e7ed085 | 157 | use crate::vec::{self, AsVecIntoIter, Vec}; |
1a4d82fc | 158 | |
04454e1e FG |
159 | #[cfg(test)] |
160 | mod tests; | |
161 | ||
1a4d82fc JJ |
162 | /// A priority queue implemented with a binary heap. |
163 | /// | |
164 | /// This will be a max-heap. | |
c34b1796 AL |
165 | /// |
166 | /// It is a logic error for an item to be modified in such a way that the | |
c295e0f8 | 167 | /// item's ordering relative to any other item, as determined by the [`Ord`] |
c34b1796 | 168 | /// trait, changes while it is in the heap. This is normally only possible |
9c376795 | 169 | /// through interior mutability, global state, I/O, or unsafe code. The |
923072b8 FG |
170 | /// behavior resulting from such a logic error is not specified, but will |
171 | /// be encapsulated to the `BinaryHeap` that observed the logic error and not | |
172 | /// result in undefined behavior. This could include panics, incorrect results, | |
173 | /// aborts, memory leaks, and non-termination. | |
54a0048b | 174 | /// |
9c376795 FG |
175 | /// As long as no elements change their relative order while being in the heap |
176 | /// as described above, the API of `BinaryHeap` guarantees that the heap | |
177 | /// invariant remains intact i.e. its methods all behave as documented. For | |
178 | /// example if a method is documented as iterating in sorted order, that's | |
179 | /// guaranteed to work as long as elements in the heap have not changed order, | |
180 | /// even in the presence of closures getting unwinded out of, iterators getting | |
181 | /// leaked, and similar foolishness. | |
182 | /// | |
54a0048b SL |
183 | /// # Examples |
184 | /// | |
185 | /// ``` | |
186 | /// use std::collections::BinaryHeap; | |
187 | /// | |
188 | /// // Type inference lets us omit an explicit type signature (which | |
189 | /// // would be `BinaryHeap<i32>` in this example). | |
190 | /// let mut heap = BinaryHeap::new(); | |
191 | /// | |
192 | /// // We can use peek to look at the next item in the heap. In this case, | |
193 | /// // there's no items in there yet so we get None. | |
194 | /// assert_eq!(heap.peek(), None); | |
195 | /// | |
196 | /// // Let's add some scores... | |
197 | /// heap.push(1); | |
198 | /// heap.push(5); | |
199 | /// heap.push(2); | |
200 | /// | |
201 | /// // Now peek shows the most important item in the heap. | |
202 | /// assert_eq!(heap.peek(), Some(&5)); | |
203 | /// | |
204 | /// // We can check the length of a heap. | |
205 | /// assert_eq!(heap.len(), 3); | |
206 | /// | |
207 | /// // We can iterate over the items in the heap, although they are returned in | |
208 | /// // a random order. | |
209 | /// for x in &heap { | |
5e7ed085 | 210 | /// println!("{x}"); |
54a0048b SL |
211 | /// } |
212 | /// | |
213 | /// // If we instead pop these scores, they should come back in order. | |
214 | /// assert_eq!(heap.pop(), Some(5)); | |
215 | /// assert_eq!(heap.pop(), Some(2)); | |
216 | /// assert_eq!(heap.pop(), Some(1)); | |
217 | /// assert_eq!(heap.pop(), None); | |
218 | /// | |
219 | /// // We can clear the heap of any remaining items. | |
220 | /// heap.clear(); | |
221 | /// | |
222 | /// // The heap should now be empty. | |
223 | /// assert!(heap.is_empty()) | |
224 | /// ``` | |
48663c56 | 225 | /// |
94222f64 XL |
226 | /// A `BinaryHeap` with a known list of items can be initialized from an array: |
227 | /// | |
228 | /// ``` | |
229 | /// use std::collections::BinaryHeap; | |
230 | /// | |
231 | /// let heap = BinaryHeap::from([1, 5, 2]); | |
232 | /// ``` | |
233 | /// | |
48663c56 XL |
234 | /// ## Min-heap |
235 | /// | |
c295e0f8 | 236 | /// Either [`core::cmp::Reverse`] or a custom [`Ord`] implementation can be used to |
48663c56 XL |
237 | /// make `BinaryHeap` a min-heap. This makes `heap.pop()` return the smallest |
238 | /// value instead of the greatest one. | |
239 | /// | |
240 | /// ``` | |
241 | /// use std::collections::BinaryHeap; | |
242 | /// use std::cmp::Reverse; | |
243 | /// | |
244 | /// let mut heap = BinaryHeap::new(); | |
245 | /// | |
246 | /// // Wrap values in `Reverse` | |
247 | /// heap.push(Reverse(1)); | |
248 | /// heap.push(Reverse(5)); | |
249 | /// heap.push(Reverse(2)); | |
250 | /// | |
251 | /// // If we pop these scores now, they should come back in the reverse order. | |
252 | /// assert_eq!(heap.pop(), Some(Reverse(1))); | |
253 | /// assert_eq!(heap.pop(), Some(Reverse(2))); | |
254 | /// assert_eq!(heap.pop(), Some(Reverse(5))); | |
255 | /// assert_eq!(heap.pop(), None); | |
256 | /// ``` | |
257 | /// | |
258 | /// # Time complexity | |
259 | /// | |
c295e0f8 XL |
260 | /// | [push] | [pop] | [peek]/[peek\_mut] | |
261 | /// |---------|---------------|--------------------| | |
262 | /// | *O*(1)~ | *O*(log(*n*)) | *O*(1) | | |
48663c56 XL |
263 | /// |
264 | /// The value for `push` is an expected cost; the method documentation gives a | |
265 | /// more detailed analysis. | |
266 | /// | |
c295e0f8 | 267 | /// [`core::cmp::Reverse`]: core::cmp::Reverse |
c295e0f8 XL |
268 | /// [`Cell`]: core::cell::Cell |
269 | /// [`RefCell`]: core::cell::RefCell | |
1b1a35ee XL |
270 | /// [push]: BinaryHeap::push |
271 | /// [pop]: BinaryHeap::pop | |
272 | /// [peek]: BinaryHeap::peek | |
273 | /// [peek\_mut]: BinaryHeap::peek_mut | |
85aaf69f | 274 | #[stable(feature = "rust1", since = "1.0.0")] |
6a06907d | 275 | #[cfg_attr(not(test), rustc_diagnostic_item = "BinaryHeap")] |
fe692bf9 FG |
276 | pub struct BinaryHeap< |
277 | T, | |
278 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
279 | > { | |
280 | data: Vec<T, A>, | |
1a4d82fc JJ |
281 | } |
282 | ||
cc61c64b XL |
283 | /// Structure wrapping a mutable reference to the greatest item on a |
284 | /// `BinaryHeap`. | |
3157f602 | 285 | /// |
cc61c64b XL |
286 | /// This `struct` is created by the [`peek_mut`] method on [`BinaryHeap`]. See |
287 | /// its documentation for more. | |
288 | /// | |
1b1a35ee | 289 | /// [`peek_mut`]: BinaryHeap::peek_mut |
5bcae85e | 290 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
fe692bf9 FG |
291 | pub struct PeekMut< |
292 | 'a, | |
293 | T: 'a + Ord, | |
294 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
295 | > { | |
296 | heap: &'a mut BinaryHeap<T, A>, | |
9c376795 FG |
297 | // If a set_len + sift_down are required, this is Some. If a &mut T has not |
298 | // yet been exposed to peek_mut()'s caller, it's None. | |
299 | original_len: Option<NonZeroUsize>, | |
3157f602 XL |
300 | } |
301 | ||
8bb4bdeb | 302 | #[stable(feature = "collection_debug", since = "1.17.0")] |
fe692bf9 | 303 | impl<T: Ord + fmt::Debug, A: Allocator> fmt::Debug for PeekMut<'_, T, A> { |
9fa01778 | 304 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
dfeec247 | 305 | f.debug_tuple("PeekMut").field(&self.heap.data[0]).finish() |
8bb4bdeb XL |
306 | } |
307 | } | |
308 | ||
5bcae85e | 309 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
fe692bf9 | 310 | impl<T: Ord, A: Allocator> Drop for PeekMut<'_, T, A> { |
3157f602 | 311 | fn drop(&mut self) { |
9c376795 FG |
312 | if let Some(original_len) = self.original_len { |
313 | // SAFETY: That's how many elements were in the Vec at the time of | |
314 | // the PeekMut::deref_mut call, and therefore also at the time of | |
315 | // the BinaryHeap::peek_mut call. Since the PeekMut did not end up | |
316 | // getting leaked, we are now undoing the leak amplification that | |
317 | // the DerefMut prepared for. | |
318 | unsafe { self.heap.data.set_len(original_len.get()) }; | |
319 | ||
6a06907d XL |
320 | // SAFETY: PeekMut is only instantiated for non-empty heaps. |
321 | unsafe { self.heap.sift_down(0) }; | |
32a655c1 | 322 | } |
3157f602 XL |
323 | } |
324 | } | |
325 | ||
5bcae85e | 326 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
fe692bf9 | 327 | impl<T: Ord, A: Allocator> Deref for PeekMut<'_, T, A> { |
3157f602 XL |
328 | type Target = T; |
329 | fn deref(&self) -> &T { | |
9fa01778 XL |
330 | debug_assert!(!self.heap.is_empty()); |
331 | // SAFE: PeekMut is only instantiated for non-empty heaps | |
332 | unsafe { self.heap.data.get_unchecked(0) } | |
3157f602 XL |
333 | } |
334 | } | |
335 | ||
5bcae85e | 336 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
fe692bf9 | 337 | impl<T: Ord, A: Allocator> DerefMut for PeekMut<'_, T, A> { |
3157f602 | 338 | fn deref_mut(&mut self) -> &mut T { |
9fa01778 | 339 | debug_assert!(!self.heap.is_empty()); |
9c376795 FG |
340 | |
341 | let len = self.heap.len(); | |
342 | if len > 1 { | |
343 | // Here we preemptively leak all the rest of the underlying vector | |
344 | // after the currently max element. If the caller mutates the &mut T | |
345 | // we're about to give them, and then leaks the PeekMut, all these | |
346 | // elements will remain leaked. If they don't leak the PeekMut, then | |
347 | // either Drop or PeekMut::pop will un-leak the vector elements. | |
348 | // | |
349 | // This is technique is described throughout several other places in | |
350 | // the standard library as "leak amplification". | |
351 | unsafe { | |
352 | // SAFETY: len > 1 so len != 0. | |
353 | self.original_len = Some(NonZeroUsize::new_unchecked(len)); | |
354 | // SAFETY: len > 1 so all this does for now is leak elements, | |
355 | // which is safe. | |
356 | self.heap.data.set_len(1); | |
357 | } | |
358 | } | |
359 | ||
9fa01778 XL |
360 | // SAFE: PeekMut is only instantiated for non-empty heaps |
361 | unsafe { self.heap.data.get_unchecked_mut(0) } | |
3157f602 XL |
362 | } |
363 | } | |
364 | ||
fe692bf9 | 365 | impl<'a, T: Ord, A: Allocator> PeekMut<'a, T, A> { |
32a655c1 | 366 | /// Removes the peeked value from the heap and returns it. |
cc61c64b | 367 | #[stable(feature = "binary_heap_peek_mut_pop", since = "1.18.0")] |
fe692bf9 | 368 | pub fn pop(mut this: PeekMut<'a, T, A>) -> T { |
9c376795 FG |
369 | if let Some(original_len) = this.original_len.take() { |
370 | // SAFETY: This is how many elements were in the Vec at the time of | |
371 | // the BinaryHeap::peek_mut call. | |
372 | unsafe { this.heap.data.set_len(original_len.get()) }; | |
373 | ||
374 | // Unlike in Drop, here we don't also need to do a sift_down even if | |
375 | // the caller could've mutated the element. It is removed from the | |
376 | // heap on the next line and pop() is not sensitive to its value. | |
377 | } | |
378 | this.heap.pop().unwrap() | |
32a655c1 SL |
379 | } |
380 | } | |
381 | ||
b039eaaf | 382 | #[stable(feature = "rust1", since = "1.0.0")] |
fe692bf9 | 383 | impl<T: Clone, A: Allocator + Clone> Clone for BinaryHeap<T, A> { |
b039eaaf SL |
384 | fn clone(&self) -> Self { |
385 | BinaryHeap { data: self.data.clone() } | |
386 | } | |
387 | ||
388 | fn clone_from(&mut self, source: &Self) { | |
389 | self.data.clone_from(&source.data); | |
390 | } | |
391 | } | |
392 | ||
85aaf69f | 393 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 394 | impl<T: Ord> Default for BinaryHeap<T> { |
9e0c209e | 395 | /// Creates an empty `BinaryHeap<T>`. |
1a4d82fc | 396 | #[inline] |
92a42be0 SL |
397 | fn default() -> BinaryHeap<T> { |
398 | BinaryHeap::new() | |
399 | } | |
1a4d82fc JJ |
400 | } |
401 | ||
e9174d1e | 402 | #[stable(feature = "binaryheap_debug", since = "1.4.0")] |
fe692bf9 | 403 | impl<T: fmt::Debug, A: Allocator> fmt::Debug for BinaryHeap<T, A> { |
9fa01778 | 404 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
e9174d1e SL |
405 | f.debug_list().entries(self.iter()).finish() |
406 | } | |
407 | } | |
408 | ||
fe692bf9 FG |
409 | struct RebuildOnDrop< |
410 | 'a, | |
411 | T: Ord, | |
412 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
413 | > { | |
414 | heap: &'a mut BinaryHeap<T, A>, | |
353b0b11 FG |
415 | rebuild_from: usize, |
416 | } | |
417 | ||
fe692bf9 | 418 | impl<T: Ord, A: Allocator> Drop for RebuildOnDrop<'_, T, A> { |
353b0b11 FG |
419 | fn drop(&mut self) { |
420 | self.heap.rebuild_tail(self.rebuild_from); | |
421 | } | |
422 | } | |
423 | ||
1a4d82fc JJ |
424 | impl<T: Ord> BinaryHeap<T> { |
425 | /// Creates an empty `BinaryHeap` as a max-heap. | |
426 | /// | |
427 | /// # Examples | |
428 | /// | |
54a0048b SL |
429 | /// Basic usage: |
430 | /// | |
1a4d82fc JJ |
431 | /// ``` |
432 | /// use std::collections::BinaryHeap; | |
433 | /// let mut heap = BinaryHeap::new(); | |
85aaf69f | 434 | /// heap.push(4); |
1a4d82fc | 435 | /// ``` |
85aaf69f | 436 | #[stable(feature = "rust1", since = "1.0.0")] |
ed00b5ec | 437 | #[rustc_const_unstable(feature = "const_binary_heap_constructor", issue = "112353")] |
c295e0f8 | 438 | #[must_use] |
ed00b5ec | 439 | pub const fn new() -> BinaryHeap<T> { |
92a42be0 SL |
440 | BinaryHeap { data: vec![] } |
441 | } | |
1a4d82fc | 442 | |
923072b8 FG |
443 | /// Creates an empty `BinaryHeap` with at least the specified capacity. |
444 | /// | |
445 | /// The binary heap will be able to hold at least `capacity` elements without | |
446 | /// reallocating. This method is allowed to allocate for more elements than | |
447 | /// `capacity`. If `capacity` is 0, the binary heap will not allocate. | |
1a4d82fc JJ |
448 | /// |
449 | /// # Examples | |
450 | /// | |
54a0048b SL |
451 | /// Basic usage: |
452 | /// | |
1a4d82fc JJ |
453 | /// ``` |
454 | /// use std::collections::BinaryHeap; | |
455 | /// let mut heap = BinaryHeap::with_capacity(10); | |
85aaf69f | 456 | /// heap.push(4); |
1a4d82fc | 457 | /// ``` |
85aaf69f | 458 | #[stable(feature = "rust1", since = "1.0.0")] |
c295e0f8 | 459 | #[must_use] |
85aaf69f | 460 | pub fn with_capacity(capacity: usize) -> BinaryHeap<T> { |
1a4d82fc JJ |
461 | BinaryHeap { data: Vec::with_capacity(capacity) } |
462 | } | |
fe692bf9 FG |
463 | } |
464 | ||
465 | impl<T: Ord, A: Allocator> BinaryHeap<T, A> { | |
466 | /// Creates an empty `BinaryHeap` as a max-heap, using `A` as allocator. | |
467 | /// | |
468 | /// # Examples | |
469 | /// | |
470 | /// Basic usage: | |
471 | /// | |
472 | /// ``` | |
473 | /// #![feature(allocator_api)] | |
474 | /// | |
475 | /// use std::alloc::System; | |
476 | /// use std::collections::BinaryHeap; | |
477 | /// let mut heap = BinaryHeap::new_in(System); | |
478 | /// heap.push(4); | |
479 | /// ``` | |
480 | #[unstable(feature = "allocator_api", issue = "32838")] | |
ed00b5ec | 481 | #[rustc_const_unstable(feature = "const_binary_heap_constructor", issue = "112353")] |
fe692bf9 | 482 | #[must_use] |
ed00b5ec | 483 | pub const fn new_in(alloc: A) -> BinaryHeap<T, A> { |
fe692bf9 FG |
484 | BinaryHeap { data: Vec::new_in(alloc) } |
485 | } | |
486 | ||
487 | /// Creates an empty `BinaryHeap` with at least the specified capacity, using `A` as allocator. | |
488 | /// | |
489 | /// The binary heap will be able to hold at least `capacity` elements without | |
490 | /// reallocating. This method is allowed to allocate for more elements than | |
491 | /// `capacity`. If `capacity` is 0, the binary heap will not allocate. | |
492 | /// | |
493 | /// # Examples | |
494 | /// | |
495 | /// Basic usage: | |
496 | /// | |
497 | /// ``` | |
498 | /// #![feature(allocator_api)] | |
499 | /// | |
500 | /// use std::alloc::System; | |
501 | /// use std::collections::BinaryHeap; | |
502 | /// let mut heap = BinaryHeap::with_capacity_in(10, System); | |
503 | /// heap.push(4); | |
504 | /// ``` | |
505 | #[unstable(feature = "allocator_api", issue = "32838")] | |
506 | #[must_use] | |
507 | pub fn with_capacity_in(capacity: usize, alloc: A) -> BinaryHeap<T, A> { | |
508 | BinaryHeap { data: Vec::with_capacity_in(capacity, alloc) } | |
509 | } | |
1a4d82fc | 510 | |
3157f602 XL |
511 | /// Returns a mutable reference to the greatest item in the binary heap, or |
512 | /// `None` if it is empty. | |
513 | /// | |
9c376795 FG |
514 | /// Note: If the `PeekMut` value is leaked, some heap elements might get |
515 | /// leaked along with it, but the remaining elements will remain a valid | |
516 | /// heap. | |
3157f602 XL |
517 | /// |
518 | /// # Examples | |
519 | /// | |
520 | /// Basic usage: | |
521 | /// | |
522 | /// ``` | |
3157f602 XL |
523 | /// use std::collections::BinaryHeap; |
524 | /// let mut heap = BinaryHeap::new(); | |
525 | /// assert!(heap.peek_mut().is_none()); | |
526 | /// | |
527 | /// heap.push(1); | |
528 | /// heap.push(5); | |
529 | /// heap.push(2); | |
530 | /// { | |
531 | /// let mut val = heap.peek_mut().unwrap(); | |
532 | /// *val = 0; | |
533 | /// } | |
534 | /// assert_eq!(heap.peek(), Some(&2)); | |
535 | /// ``` | |
48663c56 XL |
536 | /// |
537 | /// # Time complexity | |
538 | /// | |
1b1a35ee XL |
539 | /// If the item is modified then the worst case time complexity is *O*(log(*n*)), |
540 | /// otherwise it's *O*(1). | |
5bcae85e | 541 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
fe692bf9 | 542 | pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T, A>> { |
9c376795 | 543 | if self.is_empty() { None } else { Some(PeekMut { heap: self, original_len: None }) } |
3157f602 XL |
544 | } |
545 | ||
1a4d82fc JJ |
546 | /// Removes the greatest item from the binary heap and returns it, or `None` if it |
547 | /// is empty. | |
548 | /// | |
549 | /// # Examples | |
550 | /// | |
54a0048b SL |
551 | /// Basic usage: |
552 | /// | |
1a4d82fc JJ |
553 | /// ``` |
554 | /// use std::collections::BinaryHeap; | |
5099ac24 | 555 | /// let mut heap = BinaryHeap::from([1, 3]); |
1a4d82fc JJ |
556 | /// |
557 | /// assert_eq!(heap.pop(), Some(3)); | |
558 | /// assert_eq!(heap.pop(), Some(1)); | |
559 | /// assert_eq!(heap.pop(), None); | |
560 | /// ``` | |
48663c56 XL |
561 | /// |
562 | /// # Time complexity | |
563 | /// | |
3dfed10e | 564 | /// The worst case cost of `pop` on a heap containing *n* elements is *O*(log(*n*)). |
85aaf69f | 565 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
566 | pub fn pop(&mut self) -> Option<T> { |
567 | self.data.pop().map(|mut item| { | |
568 | if !self.is_empty() { | |
569 | swap(&mut item, &mut self.data[0]); | |
6a06907d XL |
570 | // SAFETY: !self.is_empty() means that self.len() > 0 |
571 | unsafe { self.sift_down_to_bottom(0) }; | |
1a4d82fc JJ |
572 | } |
573 | item | |
574 | }) | |
575 | } | |
576 | ||
577 | /// Pushes an item onto the binary heap. | |
578 | /// | |
579 | /// # Examples | |
580 | /// | |
54a0048b SL |
581 | /// Basic usage: |
582 | /// | |
1a4d82fc JJ |
583 | /// ``` |
584 | /// use std::collections::BinaryHeap; | |
585 | /// let mut heap = BinaryHeap::new(); | |
85aaf69f | 586 | /// heap.push(3); |
1a4d82fc JJ |
587 | /// heap.push(5); |
588 | /// heap.push(1); | |
589 | /// | |
590 | /// assert_eq!(heap.len(), 3); | |
591 | /// assert_eq!(heap.peek(), Some(&5)); | |
592 | /// ``` | |
48663c56 XL |
593 | /// |
594 | /// # Time complexity | |
595 | /// | |
596 | /// The expected cost of `push`, averaged over every possible ordering of | |
597 | /// the elements being pushed, and over a sufficiently large number of | |
3dfed10e | 598 | /// pushes, is *O*(1). This is the most meaningful cost metric when pushing |
48663c56 XL |
599 | /// elements that are *not* already in any sorted pattern. |
600 | /// | |
601 | /// The time complexity degrades if elements are pushed in predominantly | |
602 | /// ascending order. In the worst case, elements are pushed in ascending | |
3dfed10e | 603 | /// sorted order and the amortized cost per push is *O*(log(*n*)) against a heap |
48663c56 XL |
604 | /// containing *n* elements. |
605 | /// | |
3dfed10e | 606 | /// The worst case cost of a *single* call to `push` is *O*(*n*). The worst case |
48663c56 XL |
607 | /// occurs when capacity is exhausted and needs a resize. The resize cost |
608 | /// has been amortized in the previous figures. | |
85aaf69f | 609 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
610 | pub fn push(&mut self, item: T) { |
611 | let old_len = self.len(); | |
612 | self.data.push(item); | |
6a06907d XL |
613 | // SAFETY: Since we pushed a new item it means that |
614 | // old_len = self.len() - 1 < self.len() | |
615 | unsafe { self.sift_up(0, old_len) }; | |
1a4d82fc JJ |
616 | } |
617 | ||
1a4d82fc JJ |
618 | /// Consumes the `BinaryHeap` and returns a vector in sorted |
619 | /// (ascending) order. | |
620 | /// | |
621 | /// # Examples | |
622 | /// | |
54a0048b SL |
623 | /// Basic usage: |
624 | /// | |
1a4d82fc JJ |
625 | /// ``` |
626 | /// use std::collections::BinaryHeap; | |
627 | /// | |
5099ac24 | 628 | /// let mut heap = BinaryHeap::from([1, 2, 4, 5, 7]); |
1a4d82fc JJ |
629 | /// heap.push(6); |
630 | /// heap.push(3); | |
631 | /// | |
632 | /// let vec = heap.into_sorted_vec(); | |
c34b1796 | 633 | /// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]); |
1a4d82fc | 634 | /// ``` |
3c0e092e | 635 | #[must_use = "`self` will be dropped if the result is not used"] |
b039eaaf | 636 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
fe692bf9 | 637 | pub fn into_sorted_vec(mut self) -> Vec<T, A> { |
1a4d82fc JJ |
638 | let mut end = self.len(); |
639 | while end > 1 { | |
640 | end -= 1; | |
29967ef6 XL |
641 | // SAFETY: `end` goes from `self.len() - 1` to 1 (both included), |
642 | // so it's always a valid index to access. | |
643 | // It is safe to access index 0 (i.e. `ptr`), because | |
644 | // 1 <= end < self.len(), which means self.len() >= 2. | |
645 | unsafe { | |
646 | let ptr = self.data.as_mut_ptr(); | |
647 | ptr::swap(ptr, ptr.add(end)); | |
648 | } | |
6a06907d XL |
649 | // SAFETY: `end` goes from `self.len() - 1` to 1 (both included) so: |
650 | // 0 < 1 <= end <= self.len() - 1 < self.len() | |
651 | // Which means 0 < end and end < self.len(). | |
652 | unsafe { self.sift_down_range(0, end) }; | |
1a4d82fc JJ |
653 | } |
654 | self.into_vec() | |
655 | } | |
656 | ||
657 | // The implementations of sift_up and sift_down use unsafe blocks in | |
658 | // order to move an element out of the vector (leaving behind a | |
d9579d0f AL |
659 | // hole), shift along the others and move the removed element back into the |
660 | // vector at the final location of the hole. | |
661 | // The `Hole` type is used to represent this, and make sure | |
662 | // the hole is filled back at the end of its scope, even on panic. | |
663 | // Using a hole reduces the constant factor compared to using swaps, | |
664 | // which involves twice as many moves. | |
6a06907d XL |
665 | |
666 | /// # Safety | |
667 | /// | |
668 | /// The caller must guarantee that `pos < self.len()`. | |
669 | unsafe fn sift_up(&mut self, start: usize, pos: usize) -> usize { | |
670 | // Take out the value at `pos` and create a hole. | |
671 | // SAFETY: The caller guarantees that pos < self.len() | |
672 | let mut hole = unsafe { Hole::new(&mut self.data, pos) }; | |
673 | ||
674 | while hole.pos() > start { | |
675 | let parent = (hole.pos() - 1) / 2; | |
676 | ||
677 | // SAFETY: hole.pos() > start >= 0, which means hole.pos() > 0 | |
678 | // and so hole.pos() - 1 can't underflow. | |
679 | // This guarantees that parent < hole.pos() so | |
680 | // it's a valid index and also != hole.pos(). | |
681 | if hole.element() <= unsafe { hole.get(parent) } { | |
682 | break; | |
1a4d82fc | 683 | } |
6a06907d XL |
684 | |
685 | // SAFETY: Same as above | |
686 | unsafe { hole.move_to(parent) }; | |
1a4d82fc | 687 | } |
6a06907d XL |
688 | |
689 | hole.pos() | |
1a4d82fc JJ |
690 | } |
691 | ||
92a42be0 SL |
692 | /// Take an element at `pos` and move it down the heap, |
693 | /// while its children are larger. | |
6a06907d XL |
694 | /// |
695 | /// # Safety | |
696 | /// | |
697 | /// The caller must guarantee that `pos < end <= self.len()`. | |
698 | unsafe fn sift_down_range(&mut self, pos: usize, end: usize) { | |
699 | // SAFETY: The caller guarantees that pos < end <= self.len(). | |
700 | let mut hole = unsafe { Hole::new(&mut self.data, pos) }; | |
701 | let mut child = 2 * hole.pos() + 1; | |
702 | ||
703 | // Loop invariant: child == 2 * hole.pos() + 1. | |
704 | while child <= end.saturating_sub(2) { | |
705 | // compare with the greater of the two children | |
706 | // SAFETY: child < end - 1 < self.len() and | |
707 | // child + 1 < end <= self.len(), so they're valid indexes. | |
708 | // child == 2 * hole.pos() + 1 != hole.pos() and | |
709 | // child + 1 == 2 * hole.pos() + 2 != hole.pos(). | |
710 | // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow | |
711 | // if T is a ZST | |
712 | child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize; | |
713 | ||
714 | // if we are already in order, stop. | |
715 | // SAFETY: child is now either the old child or the old child+1 | |
716 | // We already proven that both are < self.len() and != hole.pos() | |
717 | if hole.element() >= unsafe { hole.get(child) } { | |
718 | return; | |
29967ef6 | 719 | } |
6a06907d XL |
720 | |
721 | // SAFETY: same as above. | |
722 | unsafe { hole.move_to(child) }; | |
723 | child = 2 * hole.pos() + 1; | |
724 | } | |
725 | ||
726 | // SAFETY: && short circuit, which means that in the | |
727 | // second condition it's already true that child == end - 1 < self.len(). | |
728 | if child == end - 1 && hole.element() < unsafe { hole.get(child) } { | |
729 | // SAFETY: child is already proven to be a valid index and | |
730 | // child == 2 * hole.pos() + 1 != hole.pos(). | |
731 | unsafe { hole.move_to(child) }; | |
1a4d82fc JJ |
732 | } |
733 | } | |
734 | ||
6a06907d XL |
735 | /// # Safety |
736 | /// | |
737 | /// The caller must guarantee that `pos < self.len()`. | |
738 | unsafe fn sift_down(&mut self, pos: usize) { | |
1a4d82fc | 739 | let len = self.len(); |
6a06907d XL |
740 | // SAFETY: pos < len is guaranteed by the caller and |
741 | // obviously len = self.len() <= self.len(). | |
742 | unsafe { self.sift_down_range(pos, len) }; | |
1a4d82fc JJ |
743 | } |
744 | ||
9cc50fc6 SL |
745 | /// Take an element at `pos` and move it all the way down the heap, |
746 | /// then sift it up to its position. | |
747 | /// | |
748 | /// Note: This is faster when the element is known to be large / should | |
749 | /// be closer to the bottom. | |
6a06907d XL |
750 | /// |
751 | /// # Safety | |
752 | /// | |
753 | /// The caller must guarantee that `pos < self.len()`. | |
754 | unsafe fn sift_down_to_bottom(&mut self, mut pos: usize) { | |
9cc50fc6 SL |
755 | let end = self.len(); |
756 | let start = pos; | |
6a06907d XL |
757 | |
758 | // SAFETY: The caller guarantees that pos < self.len(). | |
759 | let mut hole = unsafe { Hole::new(&mut self.data, pos) }; | |
760 | let mut child = 2 * hole.pos() + 1; | |
761 | ||
762 | // Loop invariant: child == 2 * hole.pos() + 1. | |
763 | while child <= end.saturating_sub(2) { | |
764 | // SAFETY: child < end - 1 < self.len() and | |
765 | // child + 1 < end <= self.len(), so they're valid indexes. | |
766 | // child == 2 * hole.pos() + 1 != hole.pos() and | |
767 | // child + 1 == 2 * hole.pos() + 2 != hole.pos(). | |
768 | // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow | |
769 | // if T is a ZST | |
770 | child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize; | |
771 | ||
772 | // SAFETY: Same as above | |
773 | unsafe { hole.move_to(child) }; | |
774 | child = 2 * hole.pos() + 1; | |
9cc50fc6 | 775 | } |
6a06907d XL |
776 | |
777 | if child == end - 1 { | |
778 | // SAFETY: child == end - 1 < self.len(), so it's a valid index | |
779 | // and child == 2 * hole.pos() + 1 != hole.pos(). | |
780 | unsafe { hole.move_to(child) }; | |
781 | } | |
782 | pos = hole.pos(); | |
783 | drop(hole); | |
784 | ||
785 | // SAFETY: pos is the position in the hole and was already proven | |
786 | // to be a valid index. | |
787 | unsafe { self.sift_up(start, pos) }; | |
9cc50fc6 SL |
788 | } |
789 | ||
cdc7bbd5 XL |
790 | /// Rebuild assuming data[0..start] is still a proper heap. |
791 | fn rebuild_tail(&mut self, start: usize) { | |
792 | if start == self.len() { | |
793 | return; | |
794 | } | |
795 | ||
796 | let tail_len = self.len() - start; | |
797 | ||
798 | #[inline(always)] | |
799 | fn log2_fast(x: usize) -> usize { | |
800 | (usize::BITS - x.leading_zeros() - 1) as usize | |
801 | } | |
802 | ||
803 | // `rebuild` takes O(self.len()) operations | |
804 | // and about 2 * self.len() comparisons in the worst case | |
805 | // while repeating `sift_up` takes O(tail_len * log(start)) operations | |
806 | // and about 1 * tail_len * log_2(start) comparisons in the worst case, | |
807 | // assuming start >= tail_len. For larger heaps, the crossover point | |
808 | // no longer follows this reasoning and was determined empirically. | |
809 | let better_to_rebuild = if start < tail_len { | |
810 | true | |
811 | } else if self.len() <= 2048 { | |
812 | 2 * self.len() < tail_len * log2_fast(start) | |
813 | } else { | |
814 | 2 * self.len() < tail_len * 11 | |
815 | }; | |
816 | ||
817 | if better_to_rebuild { | |
818 | self.rebuild(); | |
819 | } else { | |
820 | for i in start..self.len() { | |
821 | // SAFETY: The index `i` is always less than self.len(). | |
822 | unsafe { self.sift_up(0, i) }; | |
823 | } | |
824 | } | |
825 | } | |
826 | ||
9fa01778 XL |
827 | fn rebuild(&mut self) { |
828 | let mut n = self.len() / 2; | |
829 | while n > 0 { | |
830 | n -= 1; | |
6a06907d XL |
831 | // SAFETY: n starts from self.len() / 2 and goes down to 0. |
832 | // The only case when !(n < self.len()) is if | |
833 | // self.len() == 0, but it's ruled out by the loop condition. | |
834 | unsafe { self.sift_down(n) }; | |
9fa01778 XL |
835 | } |
836 | } | |
837 | ||
838 | /// Moves all the elements of `other` into `self`, leaving `other` empty. | |
839 | /// | |
840 | /// # Examples | |
841 | /// | |
842 | /// Basic usage: | |
843 | /// | |
844 | /// ``` | |
845 | /// use std::collections::BinaryHeap; | |
846 | /// | |
5099ac24 FG |
847 | /// let mut a = BinaryHeap::from([-10, 1, 2, 3, 3]); |
848 | /// let mut b = BinaryHeap::from([-20, 5, 43]); | |
9fa01778 XL |
849 | /// |
850 | /// a.append(&mut b); | |
851 | /// | |
852 | /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]); | |
853 | /// assert!(b.is_empty()); | |
854 | /// ``` | |
855 | #[stable(feature = "binary_heap_append", since = "1.11.0")] | |
856 | pub fn append(&mut self, other: &mut Self) { | |
857 | if self.len() < other.len() { | |
858 | swap(self, other); | |
859 | } | |
860 | ||
cdc7bbd5 | 861 | let start = self.data.len(); |
9fa01778 | 862 | |
cdc7bbd5 | 863 | self.data.append(&mut other.data); |
9fa01778 | 864 | |
cdc7bbd5 | 865 | self.rebuild_tail(start); |
9fa01778 | 866 | } |
e74abb32 | 867 | |
5099ac24 FG |
868 | /// Clears the binary heap, returning an iterator over the removed elements |
869 | /// in heap order. If the iterator is dropped before being fully consumed, | |
870 | /// it drops the remaining elements in heap order. | |
871 | /// | |
872 | /// The returned iterator keeps a mutable borrow on the heap to optimize | |
873 | /// its implementation. | |
e74abb32 XL |
874 | /// |
875 | /// Note: | |
3dfed10e | 876 | /// * `.drain_sorted()` is *O*(*n* \* log(*n*)); much slower than `.drain()`. |
e74abb32 XL |
877 | /// You should use the latter for most cases. |
878 | /// | |
879 | /// # Examples | |
880 | /// | |
881 | /// Basic usage: | |
882 | /// | |
883 | /// ``` | |
884 | /// #![feature(binary_heap_drain_sorted)] | |
885 | /// use std::collections::BinaryHeap; | |
886 | /// | |
5099ac24 | 887 | /// let mut heap = BinaryHeap::from([1, 2, 3, 4, 5]); |
e74abb32 XL |
888 | /// assert_eq!(heap.len(), 5); |
889 | /// | |
890 | /// drop(heap.drain_sorted()); // removes all elements in heap order | |
891 | /// assert_eq!(heap.len(), 0); | |
892 | /// ``` | |
893 | #[inline] | |
894 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
fe692bf9 | 895 | pub fn drain_sorted(&mut self) -> DrainSorted<'_, T, A> { |
dfeec247 | 896 | DrainSorted { inner: self } |
e74abb32 | 897 | } |
f9f354fc XL |
898 | |
899 | /// Retains only the elements specified by the predicate. | |
900 | /// | |
5e7ed085 | 901 | /// In other words, remove all elements `e` for which `f(&e)` returns |
f9f354fc XL |
902 | /// `false`. The elements are visited in unsorted (and unspecified) order. |
903 | /// | |
904 | /// # Examples | |
905 | /// | |
906 | /// Basic usage: | |
907 | /// | |
908 | /// ``` | |
f9f354fc XL |
909 | /// use std::collections::BinaryHeap; |
910 | /// | |
5099ac24 | 911 | /// let mut heap = BinaryHeap::from([-10, -5, 1, 2, 4, 13]); |
f9f354fc XL |
912 | /// |
913 | /// heap.retain(|x| x % 2 == 0); // only keep even numbers | |
914 | /// | |
915 | /// assert_eq!(heap.into_sorted_vec(), [-10, 2, 4]) | |
916 | /// ``` | |
353b0b11 | 917 | #[stable(feature = "binary_heap_retain", since = "1.70.0")] |
cdc7bbd5 | 918 | pub fn retain<F>(&mut self, mut f: F) |
f9f354fc XL |
919 | where |
920 | F: FnMut(&T) -> bool, | |
921 | { | |
353b0b11 FG |
922 | // rebuild_start will be updated to the first touched element below, and the rebuild will |
923 | // only be done for the tail. | |
924 | let mut guard = RebuildOnDrop { rebuild_from: self.len(), heap: self }; | |
cdc7bbd5 | 925 | let mut i = 0; |
353b0b11 | 926 | |
9ffffee4 | 927 | guard.heap.data.retain(|e| { |
cdc7bbd5 | 928 | let keep = f(e); |
353b0b11 FG |
929 | if !keep && i < guard.rebuild_from { |
930 | guard.rebuild_from = i; | |
cdc7bbd5 XL |
931 | } |
932 | i += 1; | |
933 | keep | |
934 | }); | |
f9f354fc | 935 | } |
9fa01778 XL |
936 | } |
937 | ||
fe692bf9 | 938 | impl<T, A: Allocator> BinaryHeap<T, A> { |
9fa01778 XL |
939 | /// Returns an iterator visiting all values in the underlying vector, in |
940 | /// arbitrary order. | |
941 | /// | |
942 | /// # Examples | |
943 | /// | |
944 | /// Basic usage: | |
945 | /// | |
946 | /// ``` | |
947 | /// use std::collections::BinaryHeap; | |
5099ac24 | 948 | /// let heap = BinaryHeap::from([1, 2, 3, 4]); |
9fa01778 XL |
949 | /// |
950 | /// // Print 1, 2, 3, 4 in arbitrary order | |
951 | /// for x in heap.iter() { | |
5e7ed085 | 952 | /// println!("{x}"); |
9fa01778 XL |
953 | /// } |
954 | /// ``` | |
955 | #[stable(feature = "rust1", since = "1.0.0")] | |
956 | pub fn iter(&self) -> Iter<'_, T> { | |
957 | Iter { iter: self.data.iter() } | |
958 | } | |
959 | ||
e74abb32 XL |
960 | /// Returns an iterator which retrieves elements in heap order. |
961 | /// This method consumes the original heap. | |
962 | /// | |
963 | /// # Examples | |
964 | /// | |
965 | /// Basic usage: | |
966 | /// | |
967 | /// ``` | |
968 | /// #![feature(binary_heap_into_iter_sorted)] | |
969 | /// use std::collections::BinaryHeap; | |
5099ac24 | 970 | /// let heap = BinaryHeap::from([1, 2, 3, 4, 5]); |
e74abb32 | 971 | /// |
5099ac24 | 972 | /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), [5, 4]); |
e74abb32 XL |
973 | /// ``` |
974 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
fe692bf9 | 975 | pub fn into_iter_sorted(self) -> IntoIterSorted<T, A> { |
dfeec247 | 976 | IntoIterSorted { inner: self } |
e74abb32 XL |
977 | } |
978 | ||
9fa01778 XL |
979 | /// Returns the greatest item in the binary heap, or `None` if it is empty. |
980 | /// | |
981 | /// # Examples | |
982 | /// | |
983 | /// Basic usage: | |
984 | /// | |
985 | /// ``` | |
986 | /// use std::collections::BinaryHeap; | |
987 | /// let mut heap = BinaryHeap::new(); | |
988 | /// assert_eq!(heap.peek(), None); | |
989 | /// | |
990 | /// heap.push(1); | |
991 | /// heap.push(5); | |
992 | /// heap.push(2); | |
993 | /// assert_eq!(heap.peek(), Some(&5)); | |
994 | /// | |
995 | /// ``` | |
48663c56 XL |
996 | /// |
997 | /// # Time complexity | |
998 | /// | |
3dfed10e | 999 | /// Cost is *O*(1) in the worst case. |
3c0e092e | 1000 | #[must_use] |
9fa01778 XL |
1001 | #[stable(feature = "rust1", since = "1.0.0")] |
1002 | pub fn peek(&self) -> Option<&T> { | |
1003 | self.data.get(0) | |
1004 | } | |
1005 | ||
1006 | /// Returns the number of elements the binary heap can hold without reallocating. | |
1007 | /// | |
1008 | /// # Examples | |
1009 | /// | |
1010 | /// Basic usage: | |
1011 | /// | |
1012 | /// ``` | |
1013 | /// use std::collections::BinaryHeap; | |
1014 | /// let mut heap = BinaryHeap::with_capacity(100); | |
1015 | /// assert!(heap.capacity() >= 100); | |
1016 | /// heap.push(4); | |
1017 | /// ``` | |
3c0e092e | 1018 | #[must_use] |
9fa01778 XL |
1019 | #[stable(feature = "rust1", since = "1.0.0")] |
1020 | pub fn capacity(&self) -> usize { | |
1021 | self.data.capacity() | |
1022 | } | |
1023 | ||
923072b8 FG |
1024 | /// Reserves the minimum capacity for at least `additional` elements more than |
1025 | /// the current length. Unlike [`reserve`], this will not | |
1026 | /// deliberately over-allocate to speculatively avoid frequent allocations. | |
1027 | /// After calling `reserve_exact`, capacity will be greater than or equal to | |
1028 | /// `self.len() + additional`. Does nothing if the capacity is already | |
1029 | /// sufficient. | |
9fa01778 | 1030 | /// |
923072b8 | 1031 | /// [`reserve`]: BinaryHeap::reserve |
9fa01778 XL |
1032 | /// |
1033 | /// # Panics | |
1034 | /// | |
923072b8 | 1035 | /// Panics if the new capacity overflows [`usize`]. |
9fa01778 XL |
1036 | /// |
1037 | /// # Examples | |
1038 | /// | |
1039 | /// Basic usage: | |
1040 | /// | |
1041 | /// ``` | |
1042 | /// use std::collections::BinaryHeap; | |
1043 | /// let mut heap = BinaryHeap::new(); | |
1044 | /// heap.reserve_exact(100); | |
1045 | /// assert!(heap.capacity() >= 100); | |
1046 | /// heap.push(4); | |
1047 | /// ``` | |
1048 | /// | |
1b1a35ee | 1049 | /// [`reserve`]: BinaryHeap::reserve |
9fa01778 XL |
1050 | #[stable(feature = "rust1", since = "1.0.0")] |
1051 | pub fn reserve_exact(&mut self, additional: usize) { | |
1052 | self.data.reserve_exact(additional); | |
1053 | } | |
1054 | ||
923072b8 FG |
1055 | /// Reserves capacity for at least `additional` elements more than the |
1056 | /// current length. The allocator may reserve more space to speculatively | |
1057 | /// avoid frequent allocations. After calling `reserve`, | |
1058 | /// capacity will be greater than or equal to `self.len() + additional`. | |
1059 | /// Does nothing if capacity is already sufficient. | |
9fa01778 XL |
1060 | /// |
1061 | /// # Panics | |
1062 | /// | |
923072b8 | 1063 | /// Panics if the new capacity overflows [`usize`]. |
9fa01778 XL |
1064 | /// |
1065 | /// # Examples | |
1066 | /// | |
1067 | /// Basic usage: | |
1068 | /// | |
1069 | /// ``` | |
1070 | /// use std::collections::BinaryHeap; | |
1071 | /// let mut heap = BinaryHeap::new(); | |
1072 | /// heap.reserve(100); | |
1073 | /// assert!(heap.capacity() >= 100); | |
1074 | /// heap.push(4); | |
1075 | /// ``` | |
1076 | #[stable(feature = "rust1", since = "1.0.0")] | |
1077 | pub fn reserve(&mut self, additional: usize) { | |
1078 | self.data.reserve(additional); | |
1079 | } | |
1080 | ||
923072b8 FG |
1081 | /// Tries to reserve the minimum capacity for at least `additional` elements |
1082 | /// more than the current length. Unlike [`try_reserve`], this will not | |
1083 | /// deliberately over-allocate to speculatively avoid frequent allocations. | |
1084 | /// After calling `try_reserve_exact`, capacity will be greater than or | |
1085 | /// equal to `self.len() + additional` if it returns `Ok(())`. | |
a2a8927a XL |
1086 | /// Does nothing if the capacity is already sufficient. |
1087 | /// | |
1088 | /// Note that the allocator may give the collection more space than it | |
1089 | /// requests. Therefore, capacity can not be relied upon to be precisely | |
1090 | /// minimal. Prefer [`try_reserve`] if future insertions are expected. | |
1091 | /// | |
1092 | /// [`try_reserve`]: BinaryHeap::try_reserve | |
1093 | /// | |
1094 | /// # Errors | |
1095 | /// | |
1096 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
1097 | /// is returned. | |
1098 | /// | |
1099 | /// # Examples | |
1100 | /// | |
1101 | /// ``` | |
a2a8927a XL |
1102 | /// use std::collections::BinaryHeap; |
1103 | /// use std::collections::TryReserveError; | |
1104 | /// | |
1105 | /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> { | |
1106 | /// let mut heap = BinaryHeap::new(); | |
1107 | /// | |
1108 | /// // Pre-reserve the memory, exiting if we can't | |
1109 | /// heap.try_reserve_exact(data.len())?; | |
1110 | /// | |
1111 | /// // Now we know this can't OOM in the middle of our complex work | |
1112 | /// heap.extend(data.iter()); | |
1113 | /// | |
1114 | /// Ok(heap.pop()) | |
1115 | /// } | |
1116 | /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); | |
1117 | /// ``` | |
923072b8 | 1118 | #[stable(feature = "try_reserve_2", since = "1.63.0")] |
a2a8927a XL |
1119 | pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { |
1120 | self.data.try_reserve_exact(additional) | |
1121 | } | |
1122 | ||
923072b8 FG |
1123 | /// Tries to reserve capacity for at least `additional` elements more than the |
1124 | /// current length. The allocator may reserve more space to speculatively | |
1125 | /// avoid frequent allocations. After calling `try_reserve`, capacity will be | |
1126 | /// greater than or equal to `self.len() + additional` if it returns | |
f2b60f7d FG |
1127 | /// `Ok(())`. Does nothing if capacity is already sufficient. This method |
1128 | /// preserves the contents even if an error occurs. | |
a2a8927a XL |
1129 | /// |
1130 | /// # Errors | |
1131 | /// | |
1132 | /// If the capacity overflows, or the allocator reports a failure, then an error | |
1133 | /// is returned. | |
1134 | /// | |
1135 | /// # Examples | |
1136 | /// | |
1137 | /// ``` | |
a2a8927a XL |
1138 | /// use std::collections::BinaryHeap; |
1139 | /// use std::collections::TryReserveError; | |
1140 | /// | |
1141 | /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> { | |
1142 | /// let mut heap = BinaryHeap::new(); | |
1143 | /// | |
1144 | /// // Pre-reserve the memory, exiting if we can't | |
1145 | /// heap.try_reserve(data.len())?; | |
1146 | /// | |
1147 | /// // Now we know this can't OOM in the middle of our complex work | |
1148 | /// heap.extend(data.iter()); | |
1149 | /// | |
1150 | /// Ok(heap.pop()) | |
1151 | /// } | |
1152 | /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); | |
1153 | /// ``` | |
923072b8 | 1154 | #[stable(feature = "try_reserve_2", since = "1.63.0")] |
a2a8927a XL |
1155 | pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { |
1156 | self.data.try_reserve(additional) | |
1157 | } | |
1158 | ||
9fa01778 XL |
1159 | /// Discards as much additional capacity as possible. |
1160 | /// | |
1161 | /// # Examples | |
1162 | /// | |
1163 | /// Basic usage: | |
1164 | /// | |
1165 | /// ``` | |
1166 | /// use std::collections::BinaryHeap; | |
1167 | /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); | |
1168 | /// | |
1169 | /// assert!(heap.capacity() >= 100); | |
1170 | /// heap.shrink_to_fit(); | |
1171 | /// assert!(heap.capacity() == 0); | |
1172 | /// ``` | |
1173 | #[stable(feature = "rust1", since = "1.0.0")] | |
1174 | pub fn shrink_to_fit(&mut self) { | |
1175 | self.data.shrink_to_fit(); | |
1176 | } | |
1177 | ||
1178 | /// Discards capacity with a lower bound. | |
1179 | /// | |
1180 | /// The capacity will remain at least as large as both the length | |
1181 | /// and the supplied value. | |
1182 | /// | |
5869c6ff | 1183 | /// If the current capacity is less than the lower limit, this is a no-op. |
9fa01778 XL |
1184 | /// |
1185 | /// # Examples | |
1186 | /// | |
1187 | /// ``` | |
9fa01778 XL |
1188 | /// use std::collections::BinaryHeap; |
1189 | /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); | |
1190 | /// | |
1191 | /// assert!(heap.capacity() >= 100); | |
1192 | /// heap.shrink_to(10); | |
1193 | /// assert!(heap.capacity() >= 10); | |
1194 | /// ``` | |
1195 | #[inline] | |
94222f64 | 1196 | #[stable(feature = "shrink_to", since = "1.56.0")] |
9fa01778 XL |
1197 | pub fn shrink_to(&mut self, min_capacity: usize) { |
1198 | self.data.shrink_to(min_capacity) | |
1199 | } | |
1200 | ||
cdc7bbd5 XL |
1201 | /// Returns a slice of all values in the underlying vector, in arbitrary |
1202 | /// order. | |
1203 | /// | |
1204 | /// # Examples | |
1205 | /// | |
1206 | /// Basic usage: | |
1207 | /// | |
1208 | /// ``` | |
1209 | /// #![feature(binary_heap_as_slice)] | |
1210 | /// use std::collections::BinaryHeap; | |
1211 | /// use std::io::{self, Write}; | |
1212 | /// | |
5099ac24 | 1213 | /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]); |
cdc7bbd5 XL |
1214 | /// |
1215 | /// io::sink().write(heap.as_slice()).unwrap(); | |
1216 | /// ``` | |
c295e0f8 | 1217 | #[must_use] |
cdc7bbd5 XL |
1218 | #[unstable(feature = "binary_heap_as_slice", issue = "83659")] |
1219 | pub fn as_slice(&self) -> &[T] { | |
1220 | self.data.as_slice() | |
1221 | } | |
1222 | ||
9fa01778 XL |
1223 | /// Consumes the `BinaryHeap` and returns the underlying vector |
1224 | /// in arbitrary order. | |
1225 | /// | |
1226 | /// # Examples | |
1227 | /// | |
1228 | /// Basic usage: | |
1229 | /// | |
1230 | /// ``` | |
1231 | /// use std::collections::BinaryHeap; | |
5099ac24 | 1232 | /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]); |
9fa01778 XL |
1233 | /// let vec = heap.into_vec(); |
1234 | /// | |
1235 | /// // Will print in some order | |
1236 | /// for x in vec { | |
5e7ed085 | 1237 | /// println!("{x}"); |
9fa01778 XL |
1238 | /// } |
1239 | /// ``` | |
c295e0f8 | 1240 | #[must_use = "`self` will be dropped if the result is not used"] |
9fa01778 | 1241 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
fe692bf9 | 1242 | pub fn into_vec(self) -> Vec<T, A> { |
9fa01778 XL |
1243 | self.into() |
1244 | } | |
1245 | ||
fe692bf9 FG |
1246 | /// Returns a reference to the underlying allocator. |
1247 | #[unstable(feature = "allocator_api", issue = "32838")] | |
1248 | #[inline] | |
1249 | pub fn allocator(&self) -> &A { | |
1250 | self.data.allocator() | |
1251 | } | |
1252 | ||
1a4d82fc | 1253 | /// Returns the length of the binary heap. |
54a0048b SL |
1254 | /// |
1255 | /// # Examples | |
1256 | /// | |
1257 | /// Basic usage: | |
1258 | /// | |
1259 | /// ``` | |
1260 | /// use std::collections::BinaryHeap; | |
5099ac24 | 1261 | /// let heap = BinaryHeap::from([1, 3]); |
54a0048b SL |
1262 | /// |
1263 | /// assert_eq!(heap.len(), 2); | |
1264 | /// ``` | |
3c0e092e | 1265 | #[must_use] |
85aaf69f | 1266 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1267 | pub fn len(&self) -> usize { |
1268 | self.data.len() | |
1269 | } | |
1a4d82fc JJ |
1270 | |
1271 | /// Checks if the binary heap is empty. | |
54a0048b SL |
1272 | /// |
1273 | /// # Examples | |
1274 | /// | |
1275 | /// Basic usage: | |
1276 | /// | |
1277 | /// ``` | |
1278 | /// use std::collections::BinaryHeap; | |
1279 | /// let mut heap = BinaryHeap::new(); | |
1280 | /// | |
1281 | /// assert!(heap.is_empty()); | |
1282 | /// | |
1283 | /// heap.push(3); | |
1284 | /// heap.push(5); | |
1285 | /// heap.push(1); | |
1286 | /// | |
1287 | /// assert!(!heap.is_empty()); | |
1288 | /// ``` | |
3c0e092e | 1289 | #[must_use] |
85aaf69f | 1290 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1291 | pub fn is_empty(&self) -> bool { |
1292 | self.len() == 0 | |
1293 | } | |
1a4d82fc | 1294 | |
5099ac24 FG |
1295 | /// Clears the binary heap, returning an iterator over the removed elements |
1296 | /// in arbitrary order. If the iterator is dropped before being fully | |
1297 | /// consumed, it drops the remaining elements in arbitrary order. | |
c34b1796 | 1298 | /// |
5099ac24 FG |
1299 | /// The returned iterator keeps a mutable borrow on the heap to optimize |
1300 | /// its implementation. | |
54a0048b SL |
1301 | /// |
1302 | /// # Examples | |
1303 | /// | |
1304 | /// Basic usage: | |
1305 | /// | |
1306 | /// ``` | |
1307 | /// use std::collections::BinaryHeap; | |
5099ac24 | 1308 | /// let mut heap = BinaryHeap::from([1, 3]); |
54a0048b SL |
1309 | /// |
1310 | /// assert!(!heap.is_empty()); | |
1311 | /// | |
1312 | /// for x in heap.drain() { | |
5e7ed085 | 1313 | /// println!("{x}"); |
54a0048b SL |
1314 | /// } |
1315 | /// | |
1316 | /// assert!(heap.is_empty()); | |
1317 | /// ``` | |
1a4d82fc | 1318 | #[inline] |
92a42be0 | 1319 | #[stable(feature = "drain", since = "1.6.0")] |
fe692bf9 | 1320 | pub fn drain(&mut self) -> Drain<'_, T, A> { |
d9579d0f | 1321 | Drain { iter: self.data.drain(..) } |
1a4d82fc JJ |
1322 | } |
1323 | ||
1324 | /// Drops all items from the binary heap. | |
54a0048b SL |
1325 | /// |
1326 | /// # Examples | |
1327 | /// | |
1328 | /// Basic usage: | |
1329 | /// | |
1330 | /// ``` | |
1331 | /// use std::collections::BinaryHeap; | |
5099ac24 | 1332 | /// let mut heap = BinaryHeap::from([1, 3]); |
54a0048b SL |
1333 | /// |
1334 | /// assert!(!heap.is_empty()); | |
1335 | /// | |
1336 | /// heap.clear(); | |
1337 | /// | |
1338 | /// assert!(heap.is_empty()); | |
1339 | /// ``` | |
85aaf69f | 1340 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
1341 | pub fn clear(&mut self) { |
1342 | self.drain(); | |
1343 | } | |
1a4d82fc JJ |
1344 | } |
1345 | ||
0731742a | 1346 | /// Hole represents a hole in a slice i.e., an index without valid value |
d9579d0f AL |
1347 | /// (because it was moved from or duplicated). |
1348 | /// In drop, `Hole` will restore the slice by filling the hole | |
1349 | /// position with the value that was originally removed. | |
1350 | struct Hole<'a, T: 'a> { | |
1351 | data: &'a mut [T], | |
83c7162d | 1352 | elt: ManuallyDrop<T>, |
d9579d0f AL |
1353 | pos: usize, |
1354 | } | |
1355 | ||
1356 | impl<'a, T> Hole<'a, T> { | |
9fa01778 | 1357 | /// Create a new `Hole` at index `pos`. |
9e0c209e SL |
1358 | /// |
1359 | /// Unsafe because pos must be within the data slice. | |
1360 | #[inline] | |
1361 | unsafe fn new(data: &'a mut [T], pos: usize) -> Self { | |
1362 | debug_assert!(pos < data.len()); | |
9fa01778 | 1363 | // SAFE: pos should be inside the slice |
f035d41b | 1364 | let elt = unsafe { ptr::read(data.get_unchecked(pos)) }; |
dfeec247 | 1365 | Hole { data, elt: ManuallyDrop::new(elt), pos } |
d9579d0f AL |
1366 | } |
1367 | ||
9e0c209e | 1368 | #[inline] |
92a42be0 SL |
1369 | fn pos(&self) -> usize { |
1370 | self.pos | |
1371 | } | |
d9579d0f | 1372 | |
cc61c64b | 1373 | /// Returns a reference to the element removed. |
9e0c209e | 1374 | #[inline] |
92a42be0 | 1375 | fn element(&self) -> &T { |
83c7162d | 1376 | &self.elt |
d9579d0f AL |
1377 | } |
1378 | ||
cc61c64b | 1379 | /// Returns a reference to the element at `index`. |
d9579d0f | 1380 | /// |
9e0c209e SL |
1381 | /// Unsafe because index must be within the data slice and not equal to pos. |
1382 | #[inline] | |
d9579d0f AL |
1383 | unsafe fn get(&self, index: usize) -> &T { |
1384 | debug_assert!(index != self.pos); | |
9e0c209e | 1385 | debug_assert!(index < self.data.len()); |
f035d41b | 1386 | unsafe { self.data.get_unchecked(index) } |
d9579d0f AL |
1387 | } |
1388 | ||
1389 | /// Move hole to new location | |
1390 | /// | |
9e0c209e SL |
1391 | /// Unsafe because index must be within the data slice and not equal to pos. |
1392 | #[inline] | |
d9579d0f AL |
1393 | unsafe fn move_to(&mut self, index: usize) { |
1394 | debug_assert!(index != self.pos); | |
9e0c209e | 1395 | debug_assert!(index < self.data.len()); |
f035d41b | 1396 | unsafe { |
29967ef6 XL |
1397 | let ptr = self.data.as_mut_ptr(); |
1398 | let index_ptr: *const _ = ptr.add(index); | |
1399 | let hole_ptr = ptr.add(self.pos); | |
f035d41b XL |
1400 | ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1); |
1401 | } | |
d9579d0f AL |
1402 | self.pos = index; |
1403 | } | |
1404 | } | |
1405 | ||
9fa01778 | 1406 | impl<T> Drop for Hole<'_, T> { |
9e0c209e | 1407 | #[inline] |
d9579d0f AL |
1408 | fn drop(&mut self) { |
1409 | // fill the hole again | |
1410 | unsafe { | |
1411 | let pos = self.pos; | |
83c7162d | 1412 | ptr::copy_nonoverlapping(&*self.elt, self.data.get_unchecked_mut(pos), 1); |
d9579d0f AL |
1413 | } |
1414 | } | |
1415 | } | |
1416 | ||
cc61c64b XL |
1417 | /// An iterator over the elements of a `BinaryHeap`. |
1418 | /// | |
1b1a35ee | 1419 | /// This `struct` is created by [`BinaryHeap::iter()`]. See its |
cc61c64b XL |
1420 | /// documentation for more. |
1421 | /// | |
1b1a35ee | 1422 | /// [`iter`]: BinaryHeap::iter |
3c0e092e | 1423 | #[must_use = "iterators are lazy and do nothing unless consumed"] |
85aaf69f | 1424 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 | 1425 | pub struct Iter<'a, T: 'a> { |
1a4d82fc JJ |
1426 | iter: slice::Iter<'a, T>, |
1427 | } | |
1428 | ||
8bb4bdeb | 1429 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
1430 | impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { |
1431 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
dfeec247 | 1432 | f.debug_tuple("Iter").field(&self.iter.as_slice()).finish() |
8bb4bdeb XL |
1433 | } |
1434 | } | |
1435 | ||
ea8adc8c | 1436 | // FIXME(#26925) Remove in favor of `#[derive(Clone)]` |
85aaf69f | 1437 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 XL |
1438 | impl<T> Clone for Iter<'_, T> { |
1439 | fn clone(&self) -> Self { | |
1a4d82fc JJ |
1440 | Iter { iter: self.iter.clone() } |
1441 | } | |
1442 | } | |
1443 | ||
85aaf69f | 1444 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1445 | impl<'a, T> Iterator for Iter<'a, T> { |
1446 | type Item = &'a T; | |
1447 | ||
1448 | #[inline] | |
92a42be0 SL |
1449 | fn next(&mut self) -> Option<&'a T> { |
1450 | self.iter.next() | |
1451 | } | |
1a4d82fc JJ |
1452 | |
1453 | #[inline] | |
92a42be0 SL |
1454 | fn size_hint(&self) -> (usize, Option<usize>) { |
1455 | self.iter.size_hint() | |
1456 | } | |
416331ca XL |
1457 | |
1458 | #[inline] | |
1459 | fn last(self) -> Option<&'a T> { | |
1460 | self.iter.last() | |
1461 | } | |
1a4d82fc JJ |
1462 | } |
1463 | ||
85aaf69f | 1464 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1465 | impl<'a, T> DoubleEndedIterator for Iter<'a, T> { |
1466 | #[inline] | |
92a42be0 SL |
1467 | fn next_back(&mut self) -> Option<&'a T> { |
1468 | self.iter.next_back() | |
1469 | } | |
1a4d82fc JJ |
1470 | } |
1471 | ||
85aaf69f | 1472 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 | 1473 | impl<T> ExactSizeIterator for Iter<'_, T> { |
476ff2be SL |
1474 | fn is_empty(&self) -> bool { |
1475 | self.iter.is_empty() | |
1476 | } | |
1477 | } | |
1a4d82fc | 1478 | |
0531ce1d | 1479 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 1480 | impl<T> FusedIterator for Iter<'_, T> {} |
9e0c209e | 1481 | |
cc61c64b XL |
1482 | /// An owning iterator over the elements of a `BinaryHeap`. |
1483 | /// | |
1b1a35ee | 1484 | /// This `struct` is created by [`BinaryHeap::into_iter()`] |
c295e0f8 | 1485 | /// (provided by the [`IntoIterator`] trait). See its documentation for more. |
cc61c64b | 1486 | /// |
1b1a35ee | 1487 | /// [`into_iter`]: BinaryHeap::into_iter |
85aaf69f | 1488 | #[stable(feature = "rust1", since = "1.0.0")] |
a7813a04 | 1489 | #[derive(Clone)] |
fe692bf9 FG |
1490 | pub struct IntoIter< |
1491 | T, | |
1492 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
1493 | > { | |
1494 | iter: vec::IntoIter<T, A>, | |
1495 | } | |
1496 | ||
1497 | impl<T, A: Allocator> IntoIter<T, A> { | |
1498 | /// Returns a reference to the underlying allocator. | |
1499 | #[unstable(feature = "allocator_api", issue = "32838")] | |
1500 | pub fn allocator(&self) -> &A { | |
1501 | self.iter.allocator() | |
1502 | } | |
1a4d82fc JJ |
1503 | } |
1504 | ||
8bb4bdeb | 1505 | #[stable(feature = "collection_debug", since = "1.17.0")] |
fe692bf9 | 1506 | impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> { |
9fa01778 | 1507 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
dfeec247 | 1508 | f.debug_tuple("IntoIter").field(&self.iter.as_slice()).finish() |
8bb4bdeb XL |
1509 | } |
1510 | } | |
1511 | ||
85aaf69f | 1512 | #[stable(feature = "rust1", since = "1.0.0")] |
fe692bf9 | 1513 | impl<T, A: Allocator> Iterator for IntoIter<T, A> { |
1a4d82fc JJ |
1514 | type Item = T; |
1515 | ||
1516 | #[inline] | |
92a42be0 SL |
1517 | fn next(&mut self) -> Option<T> { |
1518 | self.iter.next() | |
1519 | } | |
1a4d82fc JJ |
1520 | |
1521 | #[inline] | |
92a42be0 SL |
1522 | fn size_hint(&self) -> (usize, Option<usize>) { |
1523 | self.iter.size_hint() | |
1524 | } | |
1a4d82fc JJ |
1525 | } |
1526 | ||
85aaf69f | 1527 | #[stable(feature = "rust1", since = "1.0.0")] |
fe692bf9 | 1528 | impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> { |
1a4d82fc | 1529 | #[inline] |
92a42be0 SL |
1530 | fn next_back(&mut self) -> Option<T> { |
1531 | self.iter.next_back() | |
1532 | } | |
1a4d82fc JJ |
1533 | } |
1534 | ||
85aaf69f | 1535 | #[stable(feature = "rust1", since = "1.0.0")] |
fe692bf9 | 1536 | impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> { |
476ff2be SL |
1537 | fn is_empty(&self) -> bool { |
1538 | self.iter.is_empty() | |
1539 | } | |
1540 | } | |
1a4d82fc | 1541 | |
0531ce1d | 1542 | #[stable(feature = "fused", since = "1.26.0")] |
fe692bf9 | 1543 | impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {} |
9e0c209e | 1544 | |
353b0b11 FG |
1545 | #[stable(feature = "default_iters", since = "1.70.0")] |
1546 | impl<T> Default for IntoIter<T> { | |
1547 | /// Creates an empty `binary_heap::IntoIter`. | |
1548 | /// | |
1549 | /// ``` | |
1550 | /// # use std::collections::binary_heap; | |
1551 | /// let iter: binary_heap::IntoIter<u8> = Default::default(); | |
1552 | /// assert_eq!(iter.len(), 0); | |
1553 | /// ``` | |
1554 | fn default() -> Self { | |
1555 | IntoIter { iter: Default::default() } | |
1556 | } | |
1557 | } | |
1558 | ||
5e7ed085 FG |
1559 | // In addition to the SAFETY invariants of the following three unsafe traits |
1560 | // also refer to the vec::in_place_collect module documentation to get an overview | |
1b1a35ee | 1561 | #[unstable(issue = "none", feature = "inplace_iteration")] |
17df50a5 | 1562 | #[doc(hidden)] |
fe692bf9 FG |
1563 | unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> { |
1564 | type Source = IntoIter<T, A>; | |
1b1a35ee XL |
1565 | |
1566 | #[inline] | |
1567 | unsafe fn as_inner(&mut self) -> &mut Self::Source { | |
1568 | self | |
1569 | } | |
1570 | } | |
1571 | ||
1572 | #[unstable(issue = "none", feature = "inplace_iteration")] | |
17df50a5 | 1573 | #[doc(hidden)] |
fe692bf9 | 1574 | unsafe impl<I, A: Allocator> InPlaceIterable for IntoIter<I, A> {} |
1b1a35ee | 1575 | |
5e7ed085 | 1576 | unsafe impl<I> AsVecIntoIter for IntoIter<I> { |
1b1a35ee XL |
1577 | type Item = I; |
1578 | ||
1579 | fn as_into_iter(&mut self) -> &mut vec::IntoIter<Self::Item> { | |
1580 | &mut self.iter | |
1581 | } | |
1582 | } | |
1583 | ||
3c0e092e | 1584 | #[must_use = "iterators are lazy and do nothing unless consumed"] |
e74abb32 XL |
1585 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
1586 | #[derive(Clone, Debug)] | |
fe692bf9 FG |
1587 | pub struct IntoIterSorted< |
1588 | T, | |
1589 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
1590 | > { | |
1591 | inner: BinaryHeap<T, A>, | |
1592 | } | |
1593 | ||
1594 | impl<T, A: Allocator> IntoIterSorted<T, A> { | |
1595 | /// Returns a reference to the underlying allocator. | |
1596 | #[unstable(feature = "allocator_api", issue = "32838")] | |
1597 | pub fn allocator(&self) -> &A { | |
1598 | self.inner.allocator() | |
1599 | } | |
e74abb32 XL |
1600 | } |
1601 | ||
1602 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
fe692bf9 | 1603 | impl<T: Ord, A: Allocator> Iterator for IntoIterSorted<T, A> { |
e74abb32 XL |
1604 | type Item = T; |
1605 | ||
1606 | #[inline] | |
1607 | fn next(&mut self) -> Option<T> { | |
1608 | self.inner.pop() | |
1609 | } | |
1610 | ||
1611 | #[inline] | |
1612 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1613 | let exact = self.inner.len(); | |
1614 | (exact, Some(exact)) | |
1615 | } | |
1616 | } | |
1617 | ||
1618 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
fe692bf9 | 1619 | impl<T: Ord, A: Allocator> ExactSizeIterator for IntoIterSorted<T, A> {} |
e74abb32 XL |
1620 | |
1621 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
fe692bf9 | 1622 | impl<T: Ord, A: Allocator> FusedIterator for IntoIterSorted<T, A> {} |
e74abb32 XL |
1623 | |
1624 | #[unstable(feature = "trusted_len", issue = "37572")] | |
fe692bf9 | 1625 | unsafe impl<T: Ord, A: Allocator> TrustedLen for IntoIterSorted<T, A> {} |
e74abb32 | 1626 | |
cc61c64b XL |
1627 | /// A draining iterator over the elements of a `BinaryHeap`. |
1628 | /// | |
1b1a35ee | 1629 | /// This `struct` is created by [`BinaryHeap::drain()`]. See its |
cc61c64b XL |
1630 | /// documentation for more. |
1631 | /// | |
1b1a35ee | 1632 | /// [`drain`]: BinaryHeap::drain |
92a42be0 | 1633 | #[stable(feature = "drain", since = "1.6.0")] |
8bb4bdeb | 1634 | #[derive(Debug)] |
fe692bf9 FG |
1635 | pub struct Drain< |
1636 | 'a, | |
1637 | T: 'a, | |
1638 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
1639 | > { | |
1640 | iter: vec::Drain<'a, T, A>, | |
1641 | } | |
1642 | ||
1643 | impl<T, A: Allocator> Drain<'_, T, A> { | |
1644 | /// Returns a reference to the underlying allocator. | |
1645 | #[unstable(feature = "allocator_api", issue = "32838")] | |
1646 | pub fn allocator(&self) -> &A { | |
1647 | self.iter.allocator() | |
1648 | } | |
1a4d82fc JJ |
1649 | } |
1650 | ||
c30ab7b3 | 1651 | #[stable(feature = "drain", since = "1.6.0")] |
fe692bf9 | 1652 | impl<T, A: Allocator> Iterator for Drain<'_, T, A> { |
1a4d82fc JJ |
1653 | type Item = T; |
1654 | ||
1655 | #[inline] | |
92a42be0 SL |
1656 | fn next(&mut self) -> Option<T> { |
1657 | self.iter.next() | |
1658 | } | |
1a4d82fc JJ |
1659 | |
1660 | #[inline] | |
92a42be0 SL |
1661 | fn size_hint(&self) -> (usize, Option<usize>) { |
1662 | self.iter.size_hint() | |
1663 | } | |
1a4d82fc JJ |
1664 | } |
1665 | ||
c30ab7b3 | 1666 | #[stable(feature = "drain", since = "1.6.0")] |
fe692bf9 | 1667 | impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> { |
1a4d82fc | 1668 | #[inline] |
92a42be0 SL |
1669 | fn next_back(&mut self) -> Option<T> { |
1670 | self.iter.next_back() | |
1671 | } | |
1a4d82fc JJ |
1672 | } |
1673 | ||
c30ab7b3 | 1674 | #[stable(feature = "drain", since = "1.6.0")] |
fe692bf9 | 1675 | impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> { |
476ff2be SL |
1676 | fn is_empty(&self) -> bool { |
1677 | self.iter.is_empty() | |
1678 | } | |
1679 | } | |
1a4d82fc | 1680 | |
0531ce1d | 1681 | #[stable(feature = "fused", since = "1.26.0")] |
fe692bf9 | 1682 | impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {} |
9e0c209e | 1683 | |
e74abb32 XL |
1684 | /// A draining iterator over the elements of a `BinaryHeap`. |
1685 | /// | |
1b1a35ee | 1686 | /// This `struct` is created by [`BinaryHeap::drain_sorted()`]. See its |
e74abb32 XL |
1687 | /// documentation for more. |
1688 | /// | |
1b1a35ee | 1689 | /// [`drain_sorted`]: BinaryHeap::drain_sorted |
e74abb32 XL |
1690 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
1691 | #[derive(Debug)] | |
fe692bf9 FG |
1692 | pub struct DrainSorted< |
1693 | 'a, | |
1694 | T: Ord, | |
1695 | #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global, | |
1696 | > { | |
1697 | inner: &'a mut BinaryHeap<T, A>, | |
1698 | } | |
1699 | ||
1700 | impl<'a, T: Ord, A: Allocator> DrainSorted<'a, T, A> { | |
1701 | /// Returns a reference to the underlying allocator. | |
1702 | #[unstable(feature = "allocator_api", issue = "32838")] | |
1703 | pub fn allocator(&self) -> &A { | |
1704 | self.inner.allocator() | |
1705 | } | |
e74abb32 XL |
1706 | } |
1707 | ||
1708 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
fe692bf9 | 1709 | impl<'a, T: Ord, A: Allocator> Drop for DrainSorted<'a, T, A> { |
e74abb32 XL |
1710 | /// Removes heap elements in heap order. |
1711 | fn drop(&mut self) { | |
fe692bf9 | 1712 | struct DropGuard<'r, 'a, T: Ord, A: Allocator>(&'r mut DrainSorted<'a, T, A>); |
74b04a01 | 1713 | |
fe692bf9 | 1714 | impl<'r, 'a, T: Ord, A: Allocator> Drop for DropGuard<'r, 'a, T, A> { |
74b04a01 | 1715 | fn drop(&mut self) { |
f9f354fc | 1716 | while self.0.inner.pop().is_some() {} |
74b04a01 XL |
1717 | } |
1718 | } | |
1719 | ||
1720 | while let Some(item) = self.inner.pop() { | |
1721 | let guard = DropGuard(self); | |
1722 | drop(item); | |
1723 | mem::forget(guard); | |
1724 | } | |
e74abb32 XL |
1725 | } |
1726 | } | |
1727 | ||
1728 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
fe692bf9 | 1729 | impl<T: Ord, A: Allocator> Iterator for DrainSorted<'_, T, A> { |
e74abb32 XL |
1730 | type Item = T; |
1731 | ||
1732 | #[inline] | |
1733 | fn next(&mut self) -> Option<T> { | |
1734 | self.inner.pop() | |
1735 | } | |
1736 | ||
1737 | #[inline] | |
1738 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1739 | let exact = self.inner.len(); | |
1740 | (exact, Some(exact)) | |
1741 | } | |
1742 | } | |
1743 | ||
1744 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
fe692bf9 | 1745 | impl<T: Ord, A: Allocator> ExactSizeIterator for DrainSorted<'_, T, A> {} |
e74abb32 XL |
1746 | |
1747 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
fe692bf9 | 1748 | impl<T: Ord, A: Allocator> FusedIterator for DrainSorted<'_, T, A> {} |
e74abb32 XL |
1749 | |
1750 | #[unstable(feature = "trusted_len", issue = "37572")] | |
fe692bf9 | 1751 | unsafe impl<T: Ord, A: Allocator> TrustedLen for DrainSorted<'_, T, A> {} |
e74abb32 | 1752 | |
8bb4bdeb | 1753 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
fe692bf9 | 1754 | impl<T: Ord, A: Allocator> From<Vec<T, A>> for BinaryHeap<T, A> { |
e1599b0c XL |
1755 | /// Converts a `Vec<T>` into a `BinaryHeap<T>`. |
1756 | /// | |
3dfed10e | 1757 | /// This conversion happens in-place, and has *O*(*n*) time complexity. |
fe692bf9 | 1758 | fn from(vec: Vec<T, A>) -> BinaryHeap<T, A> { |
b039eaaf | 1759 | let mut heap = BinaryHeap { data: vec }; |
a7813a04 | 1760 | heap.rebuild(); |
b039eaaf SL |
1761 | heap |
1762 | } | |
1763 | } | |
94222f64 XL |
1764 | |
1765 | #[stable(feature = "std_collections_from_array", since = "1.56.0")] | |
1766 | impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T> { | |
1767 | /// ``` | |
1768 | /// use std::collections::BinaryHeap; | |
1769 | /// | |
1770 | /// let mut h1 = BinaryHeap::from([1, 4, 2, 3]); | |
1771 | /// let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into(); | |
1772 | /// while let Some((a, b)) = h1.pop().zip(h2.pop()) { | |
1773 | /// assert_eq!(a, b); | |
1774 | /// } | |
1775 | /// ``` | |
1776 | fn from(arr: [T; N]) -> Self { | |
a2a8927a | 1777 | Self::from_iter(arr) |
94222f64 XL |
1778 | } |
1779 | } | |
b039eaaf | 1780 | |
8bb4bdeb | 1781 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
fe692bf9 | 1782 | impl<T, A: Allocator> From<BinaryHeap<T, A>> for Vec<T, A> { |
1b1a35ee XL |
1783 | /// Converts a `BinaryHeap<T>` into a `Vec<T>`. |
1784 | /// | |
1785 | /// This conversion requires no data movement or allocation, and has | |
1786 | /// constant time complexity. | |
fe692bf9 | 1787 | fn from(heap: BinaryHeap<T, A>) -> Vec<T, A> { |
b039eaaf SL |
1788 | heap.data |
1789 | } | |
1790 | } | |
1791 | ||
85aaf69f | 1792 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1793 | impl<T: Ord> FromIterator<T> for BinaryHeap<T> { |
92a42be0 | 1794 | fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> { |
b039eaaf | 1795 | BinaryHeap::from(iter.into_iter().collect::<Vec<_>>()) |
85aaf69f SL |
1796 | } |
1797 | } | |
1798 | ||
1799 | #[stable(feature = "rust1", since = "1.0.0")] | |
fe692bf9 | 1800 | impl<T, A: Allocator> IntoIterator for BinaryHeap<T, A> { |
85aaf69f | 1801 | type Item = T; |
fe692bf9 | 1802 | type IntoIter = IntoIter<T, A>; |
85aaf69f | 1803 | |
9346a6ac AL |
1804 | /// Creates a consuming iterator, that is, one that moves each value out of |
1805 | /// the binary heap in arbitrary order. The binary heap cannot be used | |
1806 | /// after calling this. | |
1807 | /// | |
1808 | /// # Examples | |
1809 | /// | |
54a0048b SL |
1810 | /// Basic usage: |
1811 | /// | |
9346a6ac | 1812 | /// ``` |
9346a6ac | 1813 | /// use std::collections::BinaryHeap; |
5099ac24 | 1814 | /// let heap = BinaryHeap::from([1, 2, 3, 4]); |
9346a6ac AL |
1815 | /// |
1816 | /// // Print 1, 2, 3, 4 in arbitrary order | |
1817 | /// for x in heap.into_iter() { | |
1818 | /// // x has type i32, not &i32 | |
5e7ed085 | 1819 | /// println!("{x}"); |
9346a6ac AL |
1820 | /// } |
1821 | /// ``` | |
fe692bf9 | 1822 | fn into_iter(self) -> IntoIter<T, A> { |
9346a6ac | 1823 | IntoIter { iter: self.data.into_iter() } |
85aaf69f SL |
1824 | } |
1825 | } | |
1826 | ||
1827 | #[stable(feature = "rust1", since = "1.0.0")] | |
fe692bf9 | 1828 | impl<'a, T, A: Allocator> IntoIterator for &'a BinaryHeap<T, A> { |
85aaf69f SL |
1829 | type Item = &'a T; |
1830 | type IntoIter = Iter<'a, T>; | |
1831 | ||
1832 | fn into_iter(self) -> Iter<'a, T> { | |
1833 | self.iter() | |
1a4d82fc JJ |
1834 | } |
1835 | } | |
1836 | ||
85aaf69f | 1837 | #[stable(feature = "rust1", since = "1.0.0")] |
fe692bf9 | 1838 | impl<T: Ord, A: Allocator> Extend<T> for BinaryHeap<T, A> { |
a7813a04 | 1839 | #[inline] |
54a0048b | 1840 | fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { |
353b0b11 FG |
1841 | let guard = RebuildOnDrop { rebuild_from: self.len(), heap: self }; |
1842 | guard.heap.data.extend(iter); | |
a7813a04 | 1843 | } |
f9f354fc XL |
1844 | |
1845 | #[inline] | |
1846 | fn extend_one(&mut self, item: T) { | |
1847 | self.push(item); | |
1848 | } | |
1849 | ||
1850 | #[inline] | |
1851 | fn extend_reserve(&mut self, additional: usize) { | |
1852 | self.reserve(additional); | |
1853 | } | |
a7813a04 XL |
1854 | } |
1855 | ||
62682a34 | 1856 | #[stable(feature = "extend_ref", since = "1.2.0")] |
fe692bf9 | 1857 | impl<'a, T: 'a + Ord + Copy, A: Allocator> Extend<&'a T> for BinaryHeap<T, A> { |
92a42be0 | 1858 | fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { |
62682a34 SL |
1859 | self.extend(iter.into_iter().cloned()); |
1860 | } | |
f9f354fc XL |
1861 | |
1862 | #[inline] | |
1863 | fn extend_one(&mut self, &item: &'a T) { | |
1864 | self.push(item); | |
1865 | } | |
1866 | ||
1867 | #[inline] | |
1868 | fn extend_reserve(&mut self, additional: usize) { | |
1869 | self.reserve(additional); | |
1870 | } | |
62682a34 | 1871 | } |