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Commit | Line | Data |
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1a4d82fc JJ |
1 | //! A priority queue implemented with a binary heap. |
2 | //! | |
ba9703b0 | 3 | //! Insertion and popping the largest element have `O(log(n))` time complexity. |
62682a34 SL |
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 | |
ba9703b0 XL |
6 | //! converted to a sorted vector in-place, allowing it to be used for an `O(n * log(n))` |
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 JJ |
14 | //! |
15 | //! [dijkstra]: http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm | |
16 | //! [sssp]: http://en.wikipedia.org/wiki/Shortest_path_problem | |
17 | //! [dir_graph]: http://en.wikipedia.org/wiki/Directed_graph | |
cc61c64b | 18 | //! [`BinaryHeap`]: struct.BinaryHeap.html |
1a4d82fc JJ |
19 | //! |
20 | //! ``` | |
21 | //! use std::cmp::Ordering; | |
22 | //! use std::collections::BinaryHeap; | |
1a4d82fc | 23 | //! |
c34b1796 | 24 | //! #[derive(Copy, Clone, Eq, PartialEq)] |
1a4d82fc | 25 | //! struct State { |
85aaf69f SL |
26 | //! cost: usize, |
27 | //! position: usize, | |
1a4d82fc JJ |
28 | //! } |
29 | //! | |
30 | //! // The priority queue depends on `Ord`. | |
31 | //! // Explicitly implement the trait so the queue becomes a min-heap | |
32 | //! // instead of a max-heap. | |
33 | //! impl Ord for State { | |
34 | //! fn cmp(&self, other: &State) -> Ordering { | |
7cac9316 XL |
35 | //! // Notice that the we flip the ordering on costs. |
36 | //! // In case of a tie we compare positions - this step is necessary | |
37 | //! // to make implementations of `PartialEq` and `Ord` consistent. | |
1a4d82fc | 38 | //! other.cost.cmp(&self.cost) |
7cac9316 | 39 | //! .then_with(|| self.position.cmp(&other.position)) |
1a4d82fc JJ |
40 | //! } |
41 | //! } | |
42 | //! | |
43 | //! // `PartialOrd` needs to be implemented as well. | |
44 | //! impl PartialOrd for State { | |
45 | //! fn partial_cmp(&self, other: &State) -> Option<Ordering> { | |
46 | //! Some(self.cmp(other)) | |
47 | //! } | |
48 | //! } | |
49 | //! | |
85aaf69f | 50 | //! // Each node is represented as an `usize`, for a shorter implementation. |
1a4d82fc | 51 | //! struct Edge { |
85aaf69f SL |
52 | //! node: usize, |
53 | //! cost: usize, | |
1a4d82fc JJ |
54 | //! } |
55 | //! | |
56 | //! // Dijkstra's shortest path algorithm. | |
57 | //! | |
58 | //! // Start at `start` and use `dist` to track the current shortest distance | |
59 | //! // to each node. This implementation isn't memory-efficient as it may leave duplicate | |
85aaf69f | 60 | //! // nodes in the queue. It also uses `usize::MAX` as a sentinel value, |
1a4d82fc | 61 | //! // for a simpler implementation. |
9cc50fc6 | 62 | //! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> { |
1a4d82fc | 63 | //! // dist[node] = current shortest distance from `start` to `node` |
85aaf69f | 64 | //! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect(); |
1a4d82fc JJ |
65 | //! |
66 | //! let mut heap = BinaryHeap::new(); | |
67 | //! | |
68 | //! // We're at `start`, with a zero cost | |
69 | //! dist[start] = 0; | |
70 | //! heap.push(State { cost: 0, position: start }); | |
71 | //! | |
72 | //! // Examine the frontier with lower cost nodes first (min-heap) | |
73 | //! while let Some(State { cost, position }) = heap.pop() { | |
74 | //! // Alternatively we could have continued to find all shortest paths | |
9cc50fc6 | 75 | //! if position == goal { return Some(cost); } |
1a4d82fc JJ |
76 | //! |
77 | //! // Important as we may have already found a better way | |
78 | //! if cost > dist[position] { continue; } | |
79 | //! | |
80 | //! // For each node we can reach, see if we can find a way with | |
81 | //! // a lower cost going through this node | |
62682a34 | 82 | //! for edge in &adj_list[position] { |
1a4d82fc JJ |
83 | //! let next = State { cost: cost + edge.cost, position: edge.node }; |
84 | //! | |
85 | //! // If so, add it to the frontier and continue | |
86 | //! if next.cost < dist[next.position] { | |
87 | //! heap.push(next); | |
88 | //! // Relaxation, we have now found a better way | |
89 | //! dist[next.position] = next.cost; | |
90 | //! } | |
91 | //! } | |
92 | //! } | |
93 | //! | |
94 | //! // Goal not reachable | |
9cc50fc6 | 95 | //! None |
1a4d82fc JJ |
96 | //! } |
97 | //! | |
98 | //! fn main() { | |
99 | //! // This is the directed graph we're going to use. | |
100 | //! // The node numbers correspond to the different states, | |
101 | //! // and the edge weights symbolize the cost of moving | |
102 | //! // from one node to another. | |
103 | //! // Note that the edges are one-way. | |
104 | //! // | |
105 | //! // 7 | |
106 | //! // +-----------------+ | |
107 | //! // | | | |
e9174d1e | 108 | //! // v 1 2 | 2 |
1a4d82fc JJ |
109 | //! // 0 -----> 1 -----> 3 ---> 4 |
110 | //! // | ^ ^ ^ | |
111 | //! // | | 1 | | | |
112 | //! // | | | 3 | 1 | |
113 | //! // +------> 2 -------+ | | |
114 | //! // 10 | | | |
115 | //! // +---------------+ | |
116 | //! // | |
117 | //! // The graph is represented as an adjacency list where each index, | |
118 | //! // corresponding to a node value, has a list of outgoing edges. | |
119 | //! // Chosen for its efficiency. | |
120 | //! let graph = vec![ | |
121 | //! // Node 0 | |
122 | //! vec![Edge { node: 2, cost: 10 }, | |
123 | //! Edge { node: 1, cost: 1 }], | |
124 | //! // Node 1 | |
125 | //! vec![Edge { node: 3, cost: 2 }], | |
126 | //! // Node 2 | |
127 | //! vec![Edge { node: 1, cost: 1 }, | |
128 | //! Edge { node: 3, cost: 3 }, | |
129 | //! Edge { node: 4, cost: 1 }], | |
130 | //! // Node 3 | |
131 | //! vec![Edge { node: 0, cost: 7 }, | |
132 | //! Edge { node: 4, cost: 2 }], | |
133 | //! // Node 4 | |
134 | //! vec![]]; | |
135 | //! | |
9cc50fc6 SL |
136 | //! assert_eq!(shortest_path(&graph, 0, 1), Some(1)); |
137 | //! assert_eq!(shortest_path(&graph, 0, 3), Some(3)); | |
138 | //! assert_eq!(shortest_path(&graph, 3, 0), Some(7)); | |
139 | //! assert_eq!(shortest_path(&graph, 0, 4), Some(5)); | |
140 | //! assert_eq!(shortest_path(&graph, 4, 0), None); | |
1a4d82fc JJ |
141 | //! } |
142 | //! ``` | |
143 | ||
144 | #![allow(missing_docs)] | |
85aaf69f | 145 | #![stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 146 | |
dfeec247 | 147 | use core::fmt; |
e74abb32 | 148 | use core::iter::{FromIterator, FusedIterator, TrustedLen}; |
74b04a01 | 149 | use core::mem::{self, size_of, swap, ManuallyDrop}; |
dfeec247 | 150 | use core::ops::{Deref, DerefMut}; |
1a4d82fc JJ |
151 | use core::ptr; |
152 | ||
9fa01778 XL |
153 | use crate::slice; |
154 | use crate::vec::{self, Vec}; | |
1a4d82fc | 155 | |
a7813a04 XL |
156 | use super::SpecExtend; |
157 | ||
1a4d82fc JJ |
158 | /// A priority queue implemented with a binary heap. |
159 | /// | |
160 | /// This will be a max-heap. | |
c34b1796 AL |
161 | /// |
162 | /// It is a logic error for an item to be modified in such a way that the | |
163 | /// item's ordering relative to any other item, as determined by the `Ord` | |
164 | /// trait, changes while it is in the heap. This is normally only possible | |
165 | /// through `Cell`, `RefCell`, global state, I/O, or unsafe code. | |
54a0048b SL |
166 | /// |
167 | /// # Examples | |
168 | /// | |
169 | /// ``` | |
170 | /// use std::collections::BinaryHeap; | |
171 | /// | |
172 | /// // Type inference lets us omit an explicit type signature (which | |
173 | /// // would be `BinaryHeap<i32>` in this example). | |
174 | /// let mut heap = BinaryHeap::new(); | |
175 | /// | |
176 | /// // We can use peek to look at the next item in the heap. In this case, | |
177 | /// // there's no items in there yet so we get None. | |
178 | /// assert_eq!(heap.peek(), None); | |
179 | /// | |
180 | /// // Let's add some scores... | |
181 | /// heap.push(1); | |
182 | /// heap.push(5); | |
183 | /// heap.push(2); | |
184 | /// | |
185 | /// // Now peek shows the most important item in the heap. | |
186 | /// assert_eq!(heap.peek(), Some(&5)); | |
187 | /// | |
188 | /// // We can check the length of a heap. | |
189 | /// assert_eq!(heap.len(), 3); | |
190 | /// | |
191 | /// // We can iterate over the items in the heap, although they are returned in | |
192 | /// // a random order. | |
193 | /// for x in &heap { | |
194 | /// println!("{}", x); | |
195 | /// } | |
196 | /// | |
197 | /// // If we instead pop these scores, they should come back in order. | |
198 | /// assert_eq!(heap.pop(), Some(5)); | |
199 | /// assert_eq!(heap.pop(), Some(2)); | |
200 | /// assert_eq!(heap.pop(), Some(1)); | |
201 | /// assert_eq!(heap.pop(), None); | |
202 | /// | |
203 | /// // We can clear the heap of any remaining items. | |
204 | /// heap.clear(); | |
205 | /// | |
206 | /// // The heap should now be empty. | |
207 | /// assert!(heap.is_empty()) | |
208 | /// ``` | |
48663c56 XL |
209 | /// |
210 | /// ## Min-heap | |
211 | /// | |
212 | /// Either `std::cmp::Reverse` or a custom `Ord` implementation can be used to | |
213 | /// make `BinaryHeap` a min-heap. This makes `heap.pop()` return the smallest | |
214 | /// value instead of the greatest one. | |
215 | /// | |
216 | /// ``` | |
217 | /// use std::collections::BinaryHeap; | |
218 | /// use std::cmp::Reverse; | |
219 | /// | |
220 | /// let mut heap = BinaryHeap::new(); | |
221 | /// | |
222 | /// // Wrap values in `Reverse` | |
223 | /// heap.push(Reverse(1)); | |
224 | /// heap.push(Reverse(5)); | |
225 | /// heap.push(Reverse(2)); | |
226 | /// | |
227 | /// // If we pop these scores now, they should come back in the reverse order. | |
228 | /// assert_eq!(heap.pop(), Some(Reverse(1))); | |
229 | /// assert_eq!(heap.pop(), Some(Reverse(2))); | |
230 | /// assert_eq!(heap.pop(), Some(Reverse(5))); | |
231 | /// assert_eq!(heap.pop(), None); | |
232 | /// ``` | |
233 | /// | |
234 | /// # Time complexity | |
235 | /// | |
ba9703b0 XL |
236 | /// | [push] | [pop] | [peek]/[peek\_mut] | |
237 | /// |--------|-----------|--------------------| | |
238 | /// | O(1)~ | O(log(n)) | O(1) | | |
48663c56 XL |
239 | /// |
240 | /// The value for `push` is an expected cost; the method documentation gives a | |
241 | /// more detailed analysis. | |
242 | /// | |
243 | /// [push]: #method.push | |
244 | /// [pop]: #method.pop | |
245 | /// [peek]: #method.peek | |
246 | /// [peek\_mut]: #method.peek_mut | |
85aaf69f | 247 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
248 | pub struct BinaryHeap<T> { |
249 | data: Vec<T>, | |
250 | } | |
251 | ||
cc61c64b XL |
252 | /// Structure wrapping a mutable reference to the greatest item on a |
253 | /// `BinaryHeap`. | |
3157f602 | 254 | /// |
cc61c64b XL |
255 | /// This `struct` is created by the [`peek_mut`] method on [`BinaryHeap`]. See |
256 | /// its documentation for more. | |
257 | /// | |
258 | /// [`peek_mut`]: struct.BinaryHeap.html#method.peek_mut | |
259 | /// [`BinaryHeap`]: struct.BinaryHeap.html | |
5bcae85e | 260 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
3157f602 | 261 | pub struct PeekMut<'a, T: 'a + Ord> { |
32a655c1 SL |
262 | heap: &'a mut BinaryHeap<T>, |
263 | sift: bool, | |
3157f602 XL |
264 | } |
265 | ||
8bb4bdeb | 266 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
267 | impl<T: Ord + fmt::Debug> fmt::Debug for PeekMut<'_, T> { |
268 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
dfeec247 | 269 | f.debug_tuple("PeekMut").field(&self.heap.data[0]).finish() |
8bb4bdeb XL |
270 | } |
271 | } | |
272 | ||
5bcae85e | 273 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
9fa01778 | 274 | impl<T: Ord> Drop for PeekMut<'_, T> { |
3157f602 | 275 | fn drop(&mut self) { |
32a655c1 SL |
276 | if self.sift { |
277 | self.heap.sift_down(0); | |
278 | } | |
3157f602 XL |
279 | } |
280 | } | |
281 | ||
5bcae85e | 282 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
9fa01778 | 283 | impl<T: Ord> Deref for PeekMut<'_, T> { |
3157f602 XL |
284 | type Target = T; |
285 | fn deref(&self) -> &T { | |
9fa01778 XL |
286 | debug_assert!(!self.heap.is_empty()); |
287 | // SAFE: PeekMut is only instantiated for non-empty heaps | |
288 | unsafe { self.heap.data.get_unchecked(0) } | |
3157f602 XL |
289 | } |
290 | } | |
291 | ||
5bcae85e | 292 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
9fa01778 | 293 | impl<T: Ord> DerefMut for PeekMut<'_, T> { |
3157f602 | 294 | fn deref_mut(&mut self) -> &mut T { |
9fa01778 XL |
295 | debug_assert!(!self.heap.is_empty()); |
296 | // SAFE: PeekMut is only instantiated for non-empty heaps | |
297 | unsafe { self.heap.data.get_unchecked_mut(0) } | |
3157f602 XL |
298 | } |
299 | } | |
300 | ||
32a655c1 SL |
301 | impl<'a, T: Ord> PeekMut<'a, T> { |
302 | /// Removes the peeked value from the heap and returns it. | |
cc61c64b | 303 | #[stable(feature = "binary_heap_peek_mut_pop", since = "1.18.0")] |
32a655c1 SL |
304 | pub fn pop(mut this: PeekMut<'a, T>) -> T { |
305 | let value = this.heap.pop().unwrap(); | |
306 | this.sift = false; | |
307 | value | |
308 | } | |
309 | } | |
310 | ||
b039eaaf SL |
311 | #[stable(feature = "rust1", since = "1.0.0")] |
312 | impl<T: Clone> Clone for BinaryHeap<T> { | |
313 | fn clone(&self) -> Self { | |
314 | BinaryHeap { data: self.data.clone() } | |
315 | } | |
316 | ||
317 | fn clone_from(&mut self, source: &Self) { | |
318 | self.data.clone_from(&source.data); | |
319 | } | |
320 | } | |
321 | ||
85aaf69f | 322 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 323 | impl<T: Ord> Default for BinaryHeap<T> { |
9e0c209e | 324 | /// Creates an empty `BinaryHeap<T>`. |
1a4d82fc | 325 | #[inline] |
92a42be0 SL |
326 | fn default() -> BinaryHeap<T> { |
327 | BinaryHeap::new() | |
328 | } | |
1a4d82fc JJ |
329 | } |
330 | ||
e9174d1e | 331 | #[stable(feature = "binaryheap_debug", since = "1.4.0")] |
9fa01778 XL |
332 | impl<T: fmt::Debug> fmt::Debug for BinaryHeap<T> { |
333 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
e9174d1e SL |
334 | f.debug_list().entries(self.iter()).finish() |
335 | } | |
336 | } | |
337 | ||
1a4d82fc JJ |
338 | impl<T: Ord> BinaryHeap<T> { |
339 | /// Creates an empty `BinaryHeap` as a max-heap. | |
340 | /// | |
341 | /// # Examples | |
342 | /// | |
54a0048b SL |
343 | /// Basic usage: |
344 | /// | |
1a4d82fc JJ |
345 | /// ``` |
346 | /// use std::collections::BinaryHeap; | |
347 | /// let mut heap = BinaryHeap::new(); | |
85aaf69f | 348 | /// heap.push(4); |
1a4d82fc | 349 | /// ``` |
85aaf69f | 350 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
351 | pub fn new() -> BinaryHeap<T> { |
352 | BinaryHeap { data: vec![] } | |
353 | } | |
1a4d82fc JJ |
354 | |
355 | /// Creates an empty `BinaryHeap` with a specific capacity. | |
356 | /// This preallocates enough memory for `capacity` elements, | |
357 | /// so that the `BinaryHeap` does not have to be reallocated | |
358 | /// until it contains at least that many values. | |
359 | /// | |
360 | /// # Examples | |
361 | /// | |
54a0048b SL |
362 | /// Basic usage: |
363 | /// | |
1a4d82fc JJ |
364 | /// ``` |
365 | /// use std::collections::BinaryHeap; | |
366 | /// let mut heap = BinaryHeap::with_capacity(10); | |
85aaf69f | 367 | /// heap.push(4); |
1a4d82fc | 368 | /// ``` |
85aaf69f SL |
369 | #[stable(feature = "rust1", since = "1.0.0")] |
370 | pub fn with_capacity(capacity: usize) -> BinaryHeap<T> { | |
1a4d82fc JJ |
371 | BinaryHeap { data: Vec::with_capacity(capacity) } |
372 | } | |
373 | ||
3157f602 XL |
374 | /// Returns a mutable reference to the greatest item in the binary heap, or |
375 | /// `None` if it is empty. | |
376 | /// | |
377 | /// Note: If the `PeekMut` value is leaked, the heap may be in an | |
378 | /// inconsistent state. | |
379 | /// | |
380 | /// # Examples | |
381 | /// | |
382 | /// Basic usage: | |
383 | /// | |
384 | /// ``` | |
3157f602 XL |
385 | /// use std::collections::BinaryHeap; |
386 | /// let mut heap = BinaryHeap::new(); | |
387 | /// assert!(heap.peek_mut().is_none()); | |
388 | /// | |
389 | /// heap.push(1); | |
390 | /// heap.push(5); | |
391 | /// heap.push(2); | |
392 | /// { | |
393 | /// let mut val = heap.peek_mut().unwrap(); | |
394 | /// *val = 0; | |
395 | /// } | |
396 | /// assert_eq!(heap.peek(), Some(&2)); | |
397 | /// ``` | |
48663c56 XL |
398 | /// |
399 | /// # Time complexity | |
400 | /// | |
ba9703b0 | 401 | /// Cost is `O(1)` in the worst case. |
5bcae85e | 402 | #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
9fa01778 | 403 | pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> { |
dfeec247 | 404 | if self.is_empty() { None } else { Some(PeekMut { heap: self, sift: true }) } |
3157f602 XL |
405 | } |
406 | ||
1a4d82fc JJ |
407 | /// Removes the greatest item from the binary heap and returns it, or `None` if it |
408 | /// is empty. | |
409 | /// | |
410 | /// # Examples | |
411 | /// | |
54a0048b SL |
412 | /// Basic usage: |
413 | /// | |
1a4d82fc JJ |
414 | /// ``` |
415 | /// use std::collections::BinaryHeap; | |
b039eaaf | 416 | /// let mut heap = BinaryHeap::from(vec![1, 3]); |
1a4d82fc JJ |
417 | /// |
418 | /// assert_eq!(heap.pop(), Some(3)); | |
419 | /// assert_eq!(heap.pop(), Some(1)); | |
420 | /// assert_eq!(heap.pop(), None); | |
421 | /// ``` | |
48663c56 XL |
422 | /// |
423 | /// # Time complexity | |
424 | /// | |
ba9703b0 | 425 | /// The worst case cost of `pop` on a heap containing *n* elements is `O(log(n))`. |
85aaf69f | 426 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
427 | pub fn pop(&mut self) -> Option<T> { |
428 | self.data.pop().map(|mut item| { | |
429 | if !self.is_empty() { | |
430 | swap(&mut item, &mut self.data[0]); | |
9cc50fc6 | 431 | self.sift_down_to_bottom(0); |
1a4d82fc JJ |
432 | } |
433 | item | |
434 | }) | |
435 | } | |
436 | ||
437 | /// Pushes an item onto the binary heap. | |
438 | /// | |
439 | /// # Examples | |
440 | /// | |
54a0048b SL |
441 | /// Basic usage: |
442 | /// | |
1a4d82fc JJ |
443 | /// ``` |
444 | /// use std::collections::BinaryHeap; | |
445 | /// let mut heap = BinaryHeap::new(); | |
85aaf69f | 446 | /// heap.push(3); |
1a4d82fc JJ |
447 | /// heap.push(5); |
448 | /// heap.push(1); | |
449 | /// | |
450 | /// assert_eq!(heap.len(), 3); | |
451 | /// assert_eq!(heap.peek(), Some(&5)); | |
452 | /// ``` | |
48663c56 XL |
453 | /// |
454 | /// # Time complexity | |
455 | /// | |
456 | /// The expected cost of `push`, averaged over every possible ordering of | |
457 | /// the elements being pushed, and over a sufficiently large number of | |
ba9703b0 | 458 | /// pushes, is `O(1)`. This is the most meaningful cost metric when pushing |
48663c56 XL |
459 | /// elements that are *not* already in any sorted pattern. |
460 | /// | |
461 | /// The time complexity degrades if elements are pushed in predominantly | |
462 | /// ascending order. In the worst case, elements are pushed in ascending | |
ba9703b0 | 463 | /// sorted order and the amortized cost per push is `O(log(n))` against a heap |
48663c56 XL |
464 | /// containing *n* elements. |
465 | /// | |
ba9703b0 | 466 | /// The worst case cost of a *single* call to `push` is `O(n)`. The worst case |
48663c56 XL |
467 | /// occurs when capacity is exhausted and needs a resize. The resize cost |
468 | /// has been amortized in the previous figures. | |
85aaf69f | 469 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
470 | pub fn push(&mut self, item: T) { |
471 | let old_len = self.len(); | |
472 | self.data.push(item); | |
473 | self.sift_up(0, old_len); | |
474 | } | |
475 | ||
1a4d82fc JJ |
476 | /// Consumes the `BinaryHeap` and returns a vector in sorted |
477 | /// (ascending) order. | |
478 | /// | |
479 | /// # Examples | |
480 | /// | |
54a0048b SL |
481 | /// Basic usage: |
482 | /// | |
1a4d82fc JJ |
483 | /// ``` |
484 | /// use std::collections::BinaryHeap; | |
485 | /// | |
b039eaaf | 486 | /// let mut heap = BinaryHeap::from(vec![1, 2, 4, 5, 7]); |
1a4d82fc JJ |
487 | /// heap.push(6); |
488 | /// heap.push(3); | |
489 | /// | |
490 | /// let vec = heap.into_sorted_vec(); | |
c34b1796 | 491 | /// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]); |
1a4d82fc | 492 | /// ``` |
b039eaaf | 493 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
1a4d82fc JJ |
494 | pub fn into_sorted_vec(mut self) -> Vec<T> { |
495 | let mut end = self.len(); | |
496 | while end > 1 { | |
497 | end -= 1; | |
498 | self.data.swap(0, end); | |
499 | self.sift_down_range(0, end); | |
500 | } | |
501 | self.into_vec() | |
502 | } | |
503 | ||
504 | // The implementations of sift_up and sift_down use unsafe blocks in | |
505 | // order to move an element out of the vector (leaving behind a | |
d9579d0f AL |
506 | // hole), shift along the others and move the removed element back into the |
507 | // vector at the final location of the hole. | |
508 | // The `Hole` type is used to represent this, and make sure | |
509 | // the hole is filled back at the end of its scope, even on panic. | |
510 | // Using a hole reduces the constant factor compared to using swaps, | |
511 | // which involves twice as many moves. | |
32a655c1 | 512 | fn sift_up(&mut self, start: usize, pos: usize) -> usize { |
1a4d82fc | 513 | unsafe { |
d9579d0f AL |
514 | // Take out the value at `pos` and create a hole. |
515 | let mut hole = Hole::new(&mut self.data, pos); | |
1a4d82fc | 516 | |
d9579d0f AL |
517 | while hole.pos() > start { |
518 | let parent = (hole.pos() - 1) / 2; | |
92a42be0 SL |
519 | if hole.element() <= hole.get(parent) { |
520 | break; | |
521 | } | |
d9579d0f | 522 | hole.move_to(parent); |
1a4d82fc | 523 | } |
32a655c1 | 524 | hole.pos() |
1a4d82fc JJ |
525 | } |
526 | } | |
527 | ||
92a42be0 SL |
528 | /// Take an element at `pos` and move it down the heap, |
529 | /// while its children are larger. | |
530 | fn sift_down_range(&mut self, pos: usize, end: usize) { | |
1a4d82fc | 531 | unsafe { |
d9579d0f | 532 | let mut hole = Hole::new(&mut self.data, pos); |
1a4d82fc JJ |
533 | let mut child = 2 * pos + 1; |
534 | while child < end { | |
535 | let right = child + 1; | |
92a42be0 | 536 | // compare with the greater of the two children |
74b04a01 | 537 | if right < end && hole.get(child) <= hole.get(right) { |
1a4d82fc JJ |
538 | child = right; |
539 | } | |
92a42be0 SL |
540 | // if we are already in order, stop. |
541 | if hole.element() >= hole.get(child) { | |
542 | break; | |
543 | } | |
d9579d0f AL |
544 | hole.move_to(child); |
545 | child = 2 * hole.pos() + 1; | |
1a4d82fc | 546 | } |
1a4d82fc JJ |
547 | } |
548 | } | |
549 | ||
85aaf69f | 550 | fn sift_down(&mut self, pos: usize) { |
1a4d82fc JJ |
551 | let len = self.len(); |
552 | self.sift_down_range(pos, len); | |
553 | } | |
554 | ||
9cc50fc6 SL |
555 | /// Take an element at `pos` and move it all the way down the heap, |
556 | /// then sift it up to its position. | |
557 | /// | |
558 | /// Note: This is faster when the element is known to be large / should | |
559 | /// be closer to the bottom. | |
560 | fn sift_down_to_bottom(&mut self, mut pos: usize) { | |
561 | let end = self.len(); | |
562 | let start = pos; | |
563 | unsafe { | |
564 | let mut hole = Hole::new(&mut self.data, pos); | |
565 | let mut child = 2 * pos + 1; | |
566 | while child < end { | |
567 | let right = child + 1; | |
568 | // compare with the greater of the two children | |
74b04a01 | 569 | if right < end && hole.get(child) <= hole.get(right) { |
9cc50fc6 SL |
570 | child = right; |
571 | } | |
572 | hole.move_to(child); | |
573 | child = 2 * hole.pos() + 1; | |
574 | } | |
575 | pos = hole.pos; | |
576 | } | |
577 | self.sift_up(start, pos); | |
578 | } | |
579 | ||
9fa01778 XL |
580 | fn rebuild(&mut self) { |
581 | let mut n = self.len() / 2; | |
582 | while n > 0 { | |
583 | n -= 1; | |
584 | self.sift_down(n); | |
585 | } | |
586 | } | |
587 | ||
588 | /// Moves all the elements of `other` into `self`, leaving `other` empty. | |
589 | /// | |
590 | /// # Examples | |
591 | /// | |
592 | /// Basic usage: | |
593 | /// | |
594 | /// ``` | |
595 | /// use std::collections::BinaryHeap; | |
596 | /// | |
597 | /// let v = vec![-10, 1, 2, 3, 3]; | |
598 | /// let mut a = BinaryHeap::from(v); | |
599 | /// | |
600 | /// let v = vec![-20, 5, 43]; | |
601 | /// let mut b = BinaryHeap::from(v); | |
602 | /// | |
603 | /// a.append(&mut b); | |
604 | /// | |
605 | /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]); | |
606 | /// assert!(b.is_empty()); | |
607 | /// ``` | |
608 | #[stable(feature = "binary_heap_append", since = "1.11.0")] | |
609 | pub fn append(&mut self, other: &mut Self) { | |
610 | if self.len() < other.len() { | |
611 | swap(self, other); | |
612 | } | |
613 | ||
614 | if other.is_empty() { | |
615 | return; | |
616 | } | |
617 | ||
618 | #[inline(always)] | |
619 | fn log2_fast(x: usize) -> usize { | |
620 | 8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1 | |
621 | } | |
622 | ||
623 | // `rebuild` takes O(len1 + len2) operations | |
624 | // and about 2 * (len1 + len2) comparisons in the worst case | |
ba9703b0 | 625 | // while `extend` takes O(len2 * log(len1)) operations |
9fa01778 XL |
626 | // and about 1 * len2 * log_2(len1) comparisons in the worst case, |
627 | // assuming len1 >= len2. | |
628 | #[inline] | |
629 | fn better_to_rebuild(len1: usize, len2: usize) -> bool { | |
630 | 2 * (len1 + len2) < len2 * log2_fast(len1) | |
631 | } | |
632 | ||
633 | if better_to_rebuild(self.len(), other.len()) { | |
634 | self.data.append(&mut other.data); | |
635 | self.rebuild(); | |
636 | } else { | |
637 | self.extend(other.drain()); | |
638 | } | |
639 | } | |
e74abb32 XL |
640 | |
641 | /// Returns an iterator which retrieves elements in heap order. | |
642 | /// The retrieved elements are removed from the original heap. | |
643 | /// The remaining elements will be removed on drop in heap order. | |
644 | /// | |
645 | /// Note: | |
ba9703b0 | 646 | /// * `.drain_sorted()` is `O(n * log(n))`; much slower than `.drain()`. |
e74abb32 XL |
647 | /// You should use the latter for most cases. |
648 | /// | |
649 | /// # Examples | |
650 | /// | |
651 | /// Basic usage: | |
652 | /// | |
653 | /// ``` | |
654 | /// #![feature(binary_heap_drain_sorted)] | |
655 | /// use std::collections::BinaryHeap; | |
656 | /// | |
657 | /// let mut heap = BinaryHeap::from(vec![1, 2, 3, 4, 5]); | |
658 | /// assert_eq!(heap.len(), 5); | |
659 | /// | |
660 | /// drop(heap.drain_sorted()); // removes all elements in heap order | |
661 | /// assert_eq!(heap.len(), 0); | |
662 | /// ``` | |
663 | #[inline] | |
664 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
665 | pub fn drain_sorted(&mut self) -> DrainSorted<'_, T> { | |
dfeec247 | 666 | DrainSorted { inner: self } |
e74abb32 | 667 | } |
9fa01778 XL |
668 | } |
669 | ||
670 | impl<T> BinaryHeap<T> { | |
671 | /// Returns an iterator visiting all values in the underlying vector, in | |
672 | /// arbitrary order. | |
673 | /// | |
674 | /// # Examples | |
675 | /// | |
676 | /// Basic usage: | |
677 | /// | |
678 | /// ``` | |
679 | /// use std::collections::BinaryHeap; | |
680 | /// let heap = BinaryHeap::from(vec![1, 2, 3, 4]); | |
681 | /// | |
682 | /// // Print 1, 2, 3, 4 in arbitrary order | |
683 | /// for x in heap.iter() { | |
684 | /// println!("{}", x); | |
685 | /// } | |
686 | /// ``` | |
687 | #[stable(feature = "rust1", since = "1.0.0")] | |
688 | pub fn iter(&self) -> Iter<'_, T> { | |
689 | Iter { iter: self.data.iter() } | |
690 | } | |
691 | ||
e74abb32 XL |
692 | /// Returns an iterator which retrieves elements in heap order. |
693 | /// This method consumes the original heap. | |
694 | /// | |
695 | /// # Examples | |
696 | /// | |
697 | /// Basic usage: | |
698 | /// | |
699 | /// ``` | |
700 | /// #![feature(binary_heap_into_iter_sorted)] | |
701 | /// use std::collections::BinaryHeap; | |
702 | /// let heap = BinaryHeap::from(vec![1, 2, 3, 4, 5]); | |
703 | /// | |
704 | /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), vec![5, 4]); | |
705 | /// ``` | |
706 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
707 | pub fn into_iter_sorted(self) -> IntoIterSorted<T> { | |
dfeec247 | 708 | IntoIterSorted { inner: self } |
e74abb32 XL |
709 | } |
710 | ||
9fa01778 XL |
711 | /// Returns the greatest item in the binary heap, or `None` if it is empty. |
712 | /// | |
713 | /// # Examples | |
714 | /// | |
715 | /// Basic usage: | |
716 | /// | |
717 | /// ``` | |
718 | /// use std::collections::BinaryHeap; | |
719 | /// let mut heap = BinaryHeap::new(); | |
720 | /// assert_eq!(heap.peek(), None); | |
721 | /// | |
722 | /// heap.push(1); | |
723 | /// heap.push(5); | |
724 | /// heap.push(2); | |
725 | /// assert_eq!(heap.peek(), Some(&5)); | |
726 | /// | |
727 | /// ``` | |
48663c56 XL |
728 | /// |
729 | /// # Time complexity | |
730 | /// | |
ba9703b0 | 731 | /// Cost is `O(1)` in the worst case. |
9fa01778 XL |
732 | #[stable(feature = "rust1", since = "1.0.0")] |
733 | pub fn peek(&self) -> Option<&T> { | |
734 | self.data.get(0) | |
735 | } | |
736 | ||
737 | /// Returns the number of elements the binary heap can hold without reallocating. | |
738 | /// | |
739 | /// # Examples | |
740 | /// | |
741 | /// Basic usage: | |
742 | /// | |
743 | /// ``` | |
744 | /// use std::collections::BinaryHeap; | |
745 | /// let mut heap = BinaryHeap::with_capacity(100); | |
746 | /// assert!(heap.capacity() >= 100); | |
747 | /// heap.push(4); | |
748 | /// ``` | |
749 | #[stable(feature = "rust1", since = "1.0.0")] | |
750 | pub fn capacity(&self) -> usize { | |
751 | self.data.capacity() | |
752 | } | |
753 | ||
754 | /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the | |
755 | /// given `BinaryHeap`. Does nothing if the capacity is already sufficient. | |
756 | /// | |
757 | /// Note that the allocator may give the collection more space than it requests. Therefore | |
758 | /// capacity can not be relied upon to be precisely minimal. Prefer [`reserve`] if future | |
759 | /// insertions are expected. | |
760 | /// | |
761 | /// # Panics | |
762 | /// | |
763 | /// Panics if the new capacity overflows `usize`. | |
764 | /// | |
765 | /// # Examples | |
766 | /// | |
767 | /// Basic usage: | |
768 | /// | |
769 | /// ``` | |
770 | /// use std::collections::BinaryHeap; | |
771 | /// let mut heap = BinaryHeap::new(); | |
772 | /// heap.reserve_exact(100); | |
773 | /// assert!(heap.capacity() >= 100); | |
774 | /// heap.push(4); | |
775 | /// ``` | |
776 | /// | |
777 | /// [`reserve`]: #method.reserve | |
778 | #[stable(feature = "rust1", since = "1.0.0")] | |
779 | pub fn reserve_exact(&mut self, additional: usize) { | |
780 | self.data.reserve_exact(additional); | |
781 | } | |
782 | ||
783 | /// Reserves capacity for at least `additional` more elements to be inserted in the | |
784 | /// `BinaryHeap`. The collection may reserve more space to avoid frequent reallocations. | |
785 | /// | |
786 | /// # Panics | |
787 | /// | |
788 | /// Panics if the new capacity overflows `usize`. | |
789 | /// | |
790 | /// # Examples | |
791 | /// | |
792 | /// Basic usage: | |
793 | /// | |
794 | /// ``` | |
795 | /// use std::collections::BinaryHeap; | |
796 | /// let mut heap = BinaryHeap::new(); | |
797 | /// heap.reserve(100); | |
798 | /// assert!(heap.capacity() >= 100); | |
799 | /// heap.push(4); | |
800 | /// ``` | |
801 | #[stable(feature = "rust1", since = "1.0.0")] | |
802 | pub fn reserve(&mut self, additional: usize) { | |
803 | self.data.reserve(additional); | |
804 | } | |
805 | ||
806 | /// Discards as much additional capacity as possible. | |
807 | /// | |
808 | /// # Examples | |
809 | /// | |
810 | /// Basic usage: | |
811 | /// | |
812 | /// ``` | |
813 | /// use std::collections::BinaryHeap; | |
814 | /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); | |
815 | /// | |
816 | /// assert!(heap.capacity() >= 100); | |
817 | /// heap.shrink_to_fit(); | |
818 | /// assert!(heap.capacity() == 0); | |
819 | /// ``` | |
820 | #[stable(feature = "rust1", since = "1.0.0")] | |
821 | pub fn shrink_to_fit(&mut self) { | |
822 | self.data.shrink_to_fit(); | |
823 | } | |
824 | ||
825 | /// Discards capacity with a lower bound. | |
826 | /// | |
827 | /// The capacity will remain at least as large as both the length | |
828 | /// and the supplied value. | |
829 | /// | |
830 | /// Panics if the current capacity is smaller than the supplied | |
831 | /// minimum capacity. | |
832 | /// | |
833 | /// # Examples | |
834 | /// | |
835 | /// ``` | |
836 | /// #![feature(shrink_to)] | |
837 | /// use std::collections::BinaryHeap; | |
838 | /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); | |
839 | /// | |
840 | /// assert!(heap.capacity() >= 100); | |
841 | /// heap.shrink_to(10); | |
842 | /// assert!(heap.capacity() >= 10); | |
843 | /// ``` | |
844 | #[inline] | |
dfeec247 | 845 | #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] |
9fa01778 XL |
846 | pub fn shrink_to(&mut self, min_capacity: usize) { |
847 | self.data.shrink_to(min_capacity) | |
848 | } | |
849 | ||
850 | /// Consumes the `BinaryHeap` and returns the underlying vector | |
851 | /// in arbitrary order. | |
852 | /// | |
853 | /// # Examples | |
854 | /// | |
855 | /// Basic usage: | |
856 | /// | |
857 | /// ``` | |
858 | /// use std::collections::BinaryHeap; | |
859 | /// let heap = BinaryHeap::from(vec![1, 2, 3, 4, 5, 6, 7]); | |
860 | /// let vec = heap.into_vec(); | |
861 | /// | |
862 | /// // Will print in some order | |
863 | /// for x in vec { | |
864 | /// println!("{}", x); | |
865 | /// } | |
866 | /// ``` | |
867 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] | |
868 | pub fn into_vec(self) -> Vec<T> { | |
869 | self.into() | |
870 | } | |
871 | ||
1a4d82fc | 872 | /// Returns the length of the binary heap. |
54a0048b SL |
873 | /// |
874 | /// # Examples | |
875 | /// | |
876 | /// Basic usage: | |
877 | /// | |
878 | /// ``` | |
879 | /// use std::collections::BinaryHeap; | |
880 | /// let heap = BinaryHeap::from(vec![1, 3]); | |
881 | /// | |
882 | /// assert_eq!(heap.len(), 2); | |
883 | /// ``` | |
85aaf69f | 884 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
885 | pub fn len(&self) -> usize { |
886 | self.data.len() | |
887 | } | |
1a4d82fc JJ |
888 | |
889 | /// Checks if the binary heap is empty. | |
54a0048b SL |
890 | /// |
891 | /// # Examples | |
892 | /// | |
893 | /// Basic usage: | |
894 | /// | |
895 | /// ``` | |
896 | /// use std::collections::BinaryHeap; | |
897 | /// let mut heap = BinaryHeap::new(); | |
898 | /// | |
899 | /// assert!(heap.is_empty()); | |
900 | /// | |
901 | /// heap.push(3); | |
902 | /// heap.push(5); | |
903 | /// heap.push(1); | |
904 | /// | |
905 | /// assert!(!heap.is_empty()); | |
906 | /// ``` | |
85aaf69f | 907 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
908 | pub fn is_empty(&self) -> bool { |
909 | self.len() == 0 | |
910 | } | |
1a4d82fc JJ |
911 | |
912 | /// Clears the binary heap, returning an iterator over the removed elements. | |
c34b1796 AL |
913 | /// |
914 | /// The elements are removed in arbitrary order. | |
54a0048b SL |
915 | /// |
916 | /// # Examples | |
917 | /// | |
918 | /// Basic usage: | |
919 | /// | |
920 | /// ``` | |
921 | /// use std::collections::BinaryHeap; | |
922 | /// let mut heap = BinaryHeap::from(vec![1, 3]); | |
923 | /// | |
924 | /// assert!(!heap.is_empty()); | |
925 | /// | |
926 | /// for x in heap.drain() { | |
927 | /// println!("{}", x); | |
928 | /// } | |
929 | /// | |
930 | /// assert!(heap.is_empty()); | |
931 | /// ``` | |
1a4d82fc | 932 | #[inline] |
92a42be0 | 933 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 934 | pub fn drain(&mut self) -> Drain<'_, T> { |
d9579d0f | 935 | Drain { iter: self.data.drain(..) } |
1a4d82fc JJ |
936 | } |
937 | ||
938 | /// Drops all items from the binary heap. | |
54a0048b SL |
939 | /// |
940 | /// # Examples | |
941 | /// | |
942 | /// Basic usage: | |
943 | /// | |
944 | /// ``` | |
945 | /// use std::collections::BinaryHeap; | |
946 | /// let mut heap = BinaryHeap::from(vec![1, 3]); | |
947 | /// | |
948 | /// assert!(!heap.is_empty()); | |
949 | /// | |
950 | /// heap.clear(); | |
951 | /// | |
952 | /// assert!(heap.is_empty()); | |
953 | /// ``` | |
85aaf69f | 954 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 SL |
955 | pub fn clear(&mut self) { |
956 | self.drain(); | |
957 | } | |
1a4d82fc JJ |
958 | } |
959 | ||
0731742a | 960 | /// Hole represents a hole in a slice i.e., an index without valid value |
d9579d0f AL |
961 | /// (because it was moved from or duplicated). |
962 | /// In drop, `Hole` will restore the slice by filling the hole | |
963 | /// position with the value that was originally removed. | |
964 | struct Hole<'a, T: 'a> { | |
965 | data: &'a mut [T], | |
83c7162d | 966 | elt: ManuallyDrop<T>, |
d9579d0f AL |
967 | pos: usize, |
968 | } | |
969 | ||
970 | impl<'a, T> Hole<'a, T> { | |
9fa01778 | 971 | /// Create a new `Hole` at index `pos`. |
9e0c209e SL |
972 | /// |
973 | /// Unsafe because pos must be within the data slice. | |
974 | #[inline] | |
975 | unsafe fn new(data: &'a mut [T], pos: usize) -> Self { | |
976 | debug_assert!(pos < data.len()); | |
9fa01778 XL |
977 | // SAFE: pos should be inside the slice |
978 | let elt = ptr::read(data.get_unchecked(pos)); | |
dfeec247 | 979 | Hole { data, elt: ManuallyDrop::new(elt), pos } |
d9579d0f AL |
980 | } |
981 | ||
9e0c209e | 982 | #[inline] |
92a42be0 SL |
983 | fn pos(&self) -> usize { |
984 | self.pos | |
985 | } | |
d9579d0f | 986 | |
cc61c64b | 987 | /// Returns a reference to the element removed. |
9e0c209e | 988 | #[inline] |
92a42be0 | 989 | fn element(&self) -> &T { |
83c7162d | 990 | &self.elt |
d9579d0f AL |
991 | } |
992 | ||
cc61c64b | 993 | /// Returns a reference to the element at `index`. |
d9579d0f | 994 | /// |
9e0c209e SL |
995 | /// Unsafe because index must be within the data slice and not equal to pos. |
996 | #[inline] | |
d9579d0f AL |
997 | unsafe fn get(&self, index: usize) -> &T { |
998 | debug_assert!(index != self.pos); | |
9e0c209e SL |
999 | debug_assert!(index < self.data.len()); |
1000 | self.data.get_unchecked(index) | |
d9579d0f AL |
1001 | } |
1002 | ||
1003 | /// Move hole to new location | |
1004 | /// | |
9e0c209e SL |
1005 | /// Unsafe because index must be within the data slice and not equal to pos. |
1006 | #[inline] | |
d9579d0f AL |
1007 | unsafe fn move_to(&mut self, index: usize) { |
1008 | debug_assert!(index != self.pos); | |
9e0c209e SL |
1009 | debug_assert!(index < self.data.len()); |
1010 | let index_ptr: *const _ = self.data.get_unchecked(index); | |
1011 | let hole_ptr = self.data.get_unchecked_mut(self.pos); | |
d9579d0f AL |
1012 | ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1); |
1013 | self.pos = index; | |
1014 | } | |
1015 | } | |
1016 | ||
9fa01778 | 1017 | impl<T> Drop for Hole<'_, T> { |
9e0c209e | 1018 | #[inline] |
d9579d0f AL |
1019 | fn drop(&mut self) { |
1020 | // fill the hole again | |
1021 | unsafe { | |
1022 | let pos = self.pos; | |
83c7162d | 1023 | ptr::copy_nonoverlapping(&*self.elt, self.data.get_unchecked_mut(pos), 1); |
d9579d0f AL |
1024 | } |
1025 | } | |
1026 | } | |
1027 | ||
cc61c64b XL |
1028 | /// An iterator over the elements of a `BinaryHeap`. |
1029 | /// | |
1030 | /// This `struct` is created by the [`iter`] method on [`BinaryHeap`]. See its | |
1031 | /// documentation for more. | |
1032 | /// | |
1033 | /// [`iter`]: struct.BinaryHeap.html#method.iter | |
1034 | /// [`BinaryHeap`]: struct.BinaryHeap.html | |
85aaf69f | 1035 | #[stable(feature = "rust1", since = "1.0.0")] |
92a42be0 | 1036 | pub struct Iter<'a, T: 'a> { |
1a4d82fc JJ |
1037 | iter: slice::Iter<'a, T>, |
1038 | } | |
1039 | ||
8bb4bdeb | 1040 | #[stable(feature = "collection_debug", since = "1.17.0")] |
9fa01778 XL |
1041 | impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { |
1042 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | |
dfeec247 | 1043 | f.debug_tuple("Iter").field(&self.iter.as_slice()).finish() |
8bb4bdeb XL |
1044 | } |
1045 | } | |
1046 | ||
ea8adc8c | 1047 | // FIXME(#26925) Remove in favor of `#[derive(Clone)]` |
85aaf69f | 1048 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 XL |
1049 | impl<T> Clone for Iter<'_, T> { |
1050 | fn clone(&self) -> Self { | |
1a4d82fc JJ |
1051 | Iter { iter: self.iter.clone() } |
1052 | } | |
1053 | } | |
1054 | ||
85aaf69f | 1055 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1056 | impl<'a, T> Iterator for Iter<'a, T> { |
1057 | type Item = &'a T; | |
1058 | ||
1059 | #[inline] | |
92a42be0 SL |
1060 | fn next(&mut self) -> Option<&'a T> { |
1061 | self.iter.next() | |
1062 | } | |
1a4d82fc JJ |
1063 | |
1064 | #[inline] | |
92a42be0 SL |
1065 | fn size_hint(&self) -> (usize, Option<usize>) { |
1066 | self.iter.size_hint() | |
1067 | } | |
416331ca XL |
1068 | |
1069 | #[inline] | |
1070 | fn last(self) -> Option<&'a T> { | |
1071 | self.iter.last() | |
1072 | } | |
1a4d82fc JJ |
1073 | } |
1074 | ||
85aaf69f | 1075 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1076 | impl<'a, T> DoubleEndedIterator for Iter<'a, T> { |
1077 | #[inline] | |
92a42be0 SL |
1078 | fn next_back(&mut self) -> Option<&'a T> { |
1079 | self.iter.next_back() | |
1080 | } | |
1a4d82fc JJ |
1081 | } |
1082 | ||
85aaf69f | 1083 | #[stable(feature = "rust1", since = "1.0.0")] |
9fa01778 | 1084 | impl<T> ExactSizeIterator for Iter<'_, T> { |
476ff2be SL |
1085 | fn is_empty(&self) -> bool { |
1086 | self.iter.is_empty() | |
1087 | } | |
1088 | } | |
1a4d82fc | 1089 | |
0531ce1d | 1090 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 1091 | impl<T> FusedIterator for Iter<'_, T> {} |
9e0c209e | 1092 | |
cc61c64b XL |
1093 | /// An owning iterator over the elements of a `BinaryHeap`. |
1094 | /// | |
dfeec247 | 1095 | /// This `struct` is created by the [`into_iter`] method on [`BinaryHeap`] |
cc61c64b XL |
1096 | /// (provided by the `IntoIterator` trait). See its documentation for more. |
1097 | /// | |
1098 | /// [`into_iter`]: struct.BinaryHeap.html#method.into_iter | |
1099 | /// [`BinaryHeap`]: struct.BinaryHeap.html | |
85aaf69f | 1100 | #[stable(feature = "rust1", since = "1.0.0")] |
a7813a04 | 1101 | #[derive(Clone)] |
1a4d82fc JJ |
1102 | pub struct IntoIter<T> { |
1103 | iter: vec::IntoIter<T>, | |
1104 | } | |
1105 | ||
8bb4bdeb XL |
1106 | #[stable(feature = "collection_debug", since = "1.17.0")] |
1107 | impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { | |
9fa01778 | 1108 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
dfeec247 | 1109 | f.debug_tuple("IntoIter").field(&self.iter.as_slice()).finish() |
8bb4bdeb XL |
1110 | } |
1111 | } | |
1112 | ||
85aaf69f | 1113 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1114 | impl<T> Iterator for IntoIter<T> { |
1115 | type Item = T; | |
1116 | ||
1117 | #[inline] | |
92a42be0 SL |
1118 | fn next(&mut self) -> Option<T> { |
1119 | self.iter.next() | |
1120 | } | |
1a4d82fc JJ |
1121 | |
1122 | #[inline] | |
92a42be0 SL |
1123 | fn size_hint(&self) -> (usize, Option<usize>) { |
1124 | self.iter.size_hint() | |
1125 | } | |
1a4d82fc JJ |
1126 | } |
1127 | ||
85aaf69f | 1128 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc JJ |
1129 | impl<T> DoubleEndedIterator for IntoIter<T> { |
1130 | #[inline] | |
92a42be0 SL |
1131 | fn next_back(&mut self) -> Option<T> { |
1132 | self.iter.next_back() | |
1133 | } | |
1a4d82fc JJ |
1134 | } |
1135 | ||
85aaf69f | 1136 | #[stable(feature = "rust1", since = "1.0.0")] |
476ff2be SL |
1137 | impl<T> ExactSizeIterator for IntoIter<T> { |
1138 | fn is_empty(&self) -> bool { | |
1139 | self.iter.is_empty() | |
1140 | } | |
1141 | } | |
1a4d82fc | 1142 | |
0531ce1d | 1143 | #[stable(feature = "fused", since = "1.26.0")] |
9e0c209e SL |
1144 | impl<T> FusedIterator for IntoIter<T> {} |
1145 | ||
e74abb32 XL |
1146 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
1147 | #[derive(Clone, Debug)] | |
1148 | pub struct IntoIterSorted<T> { | |
1149 | inner: BinaryHeap<T>, | |
1150 | } | |
1151 | ||
1152 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
1153 | impl<T: Ord> Iterator for IntoIterSorted<T> { | |
1154 | type Item = T; | |
1155 | ||
1156 | #[inline] | |
1157 | fn next(&mut self) -> Option<T> { | |
1158 | self.inner.pop() | |
1159 | } | |
1160 | ||
1161 | #[inline] | |
1162 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1163 | let exact = self.inner.len(); | |
1164 | (exact, Some(exact)) | |
1165 | } | |
1166 | } | |
1167 | ||
1168 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
1169 | impl<T: Ord> ExactSizeIterator for IntoIterSorted<T> {} | |
1170 | ||
1171 | #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] | |
1172 | impl<T: Ord> FusedIterator for IntoIterSorted<T> {} | |
1173 | ||
1174 | #[unstable(feature = "trusted_len", issue = "37572")] | |
1175 | unsafe impl<T: Ord> TrustedLen for IntoIterSorted<T> {} | |
1176 | ||
cc61c64b XL |
1177 | /// A draining iterator over the elements of a `BinaryHeap`. |
1178 | /// | |
1179 | /// This `struct` is created by the [`drain`] method on [`BinaryHeap`]. See its | |
1180 | /// documentation for more. | |
1181 | /// | |
1182 | /// [`drain`]: struct.BinaryHeap.html#method.drain | |
1183 | /// [`BinaryHeap`]: struct.BinaryHeap.html | |
92a42be0 | 1184 | #[stable(feature = "drain", since = "1.6.0")] |
8bb4bdeb | 1185 | #[derive(Debug)] |
1a4d82fc JJ |
1186 | pub struct Drain<'a, T: 'a> { |
1187 | iter: vec::Drain<'a, T>, | |
1188 | } | |
1189 | ||
c30ab7b3 | 1190 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1191 | impl<T> Iterator for Drain<'_, T> { |
1a4d82fc JJ |
1192 | type Item = T; |
1193 | ||
1194 | #[inline] | |
92a42be0 SL |
1195 | fn next(&mut self) -> Option<T> { |
1196 | self.iter.next() | |
1197 | } | |
1a4d82fc JJ |
1198 | |
1199 | #[inline] | |
92a42be0 SL |
1200 | fn size_hint(&self) -> (usize, Option<usize>) { |
1201 | self.iter.size_hint() | |
1202 | } | |
1a4d82fc JJ |
1203 | } |
1204 | ||
c30ab7b3 | 1205 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1206 | impl<T> DoubleEndedIterator for Drain<'_, T> { |
1a4d82fc | 1207 | #[inline] |
92a42be0 SL |
1208 | fn next_back(&mut self) -> Option<T> { |
1209 | self.iter.next_back() | |
1210 | } | |
1a4d82fc JJ |
1211 | } |
1212 | ||
c30ab7b3 | 1213 | #[stable(feature = "drain", since = "1.6.0")] |
9fa01778 | 1214 | impl<T> ExactSizeIterator for Drain<'_, T> { |
476ff2be SL |
1215 | fn is_empty(&self) -> bool { |
1216 | self.iter.is_empty() | |
1217 | } | |
1218 | } | |
1a4d82fc | 1219 | |
0531ce1d | 1220 | #[stable(feature = "fused", since = "1.26.0")] |
9fa01778 | 1221 | impl<T> FusedIterator for Drain<'_, T> {} |
9e0c209e | 1222 | |
e74abb32 XL |
1223 | /// A draining iterator over the elements of a `BinaryHeap`. |
1224 | /// | |
1225 | /// This `struct` is created by the [`drain_sorted`] method on [`BinaryHeap`]. See its | |
1226 | /// documentation for more. | |
1227 | /// | |
1228 | /// [`drain_sorted`]: struct.BinaryHeap.html#method.drain_sorted | |
1229 | /// [`BinaryHeap`]: struct.BinaryHeap.html | |
1230 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
1231 | #[derive(Debug)] | |
1232 | pub struct DrainSorted<'a, T: Ord> { | |
1233 | inner: &'a mut BinaryHeap<T>, | |
1234 | } | |
1235 | ||
1236 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
1237 | impl<'a, T: Ord> Drop for DrainSorted<'a, T> { | |
1238 | /// Removes heap elements in heap order. | |
1239 | fn drop(&mut self) { | |
74b04a01 XL |
1240 | struct DropGuard<'r, 'a, T: Ord>(&'r mut DrainSorted<'a, T>); |
1241 | ||
1242 | impl<'r, 'a, T: Ord> Drop for DropGuard<'r, 'a, T> { | |
1243 | fn drop(&mut self) { | |
1244 | while let Some(_) = self.0.inner.pop() {} | |
1245 | } | |
1246 | } | |
1247 | ||
1248 | while let Some(item) = self.inner.pop() { | |
1249 | let guard = DropGuard(self); | |
1250 | drop(item); | |
1251 | mem::forget(guard); | |
1252 | } | |
e74abb32 XL |
1253 | } |
1254 | } | |
1255 | ||
1256 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
1257 | impl<T: Ord> Iterator for DrainSorted<'_, T> { | |
1258 | type Item = T; | |
1259 | ||
1260 | #[inline] | |
1261 | fn next(&mut self) -> Option<T> { | |
1262 | self.inner.pop() | |
1263 | } | |
1264 | ||
1265 | #[inline] | |
1266 | fn size_hint(&self) -> (usize, Option<usize>) { | |
1267 | let exact = self.inner.len(); | |
1268 | (exact, Some(exact)) | |
1269 | } | |
1270 | } | |
1271 | ||
1272 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
dfeec247 | 1273 | impl<T: Ord> ExactSizeIterator for DrainSorted<'_, T> {} |
e74abb32 XL |
1274 | |
1275 | #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] | |
1276 | impl<T: Ord> FusedIterator for DrainSorted<'_, T> {} | |
1277 | ||
1278 | #[unstable(feature = "trusted_len", issue = "37572")] | |
1279 | unsafe impl<T: Ord> TrustedLen for DrainSorted<'_, T> {} | |
1280 | ||
8bb4bdeb | 1281 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
b039eaaf | 1282 | impl<T: Ord> From<Vec<T>> for BinaryHeap<T> { |
e1599b0c XL |
1283 | /// Converts a `Vec<T>` into a `BinaryHeap<T>`. |
1284 | /// | |
1285 | /// This conversion happens in-place, and has `O(n)` time complexity. | |
b039eaaf SL |
1286 | fn from(vec: Vec<T>) -> BinaryHeap<T> { |
1287 | let mut heap = BinaryHeap { data: vec }; | |
a7813a04 | 1288 | heap.rebuild(); |
b039eaaf SL |
1289 | heap |
1290 | } | |
1291 | } | |
1292 | ||
8bb4bdeb | 1293 | #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
b039eaaf SL |
1294 | impl<T> From<BinaryHeap<T>> for Vec<T> { |
1295 | fn from(heap: BinaryHeap<T>) -> Vec<T> { | |
1296 | heap.data | |
1297 | } | |
1298 | } | |
1299 | ||
85aaf69f | 1300 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1301 | impl<T: Ord> FromIterator<T> for BinaryHeap<T> { |
92a42be0 | 1302 | fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> { |
b039eaaf | 1303 | BinaryHeap::from(iter.into_iter().collect::<Vec<_>>()) |
85aaf69f SL |
1304 | } |
1305 | } | |
1306 | ||
1307 | #[stable(feature = "rust1", since = "1.0.0")] | |
9fa01778 | 1308 | impl<T> IntoIterator for BinaryHeap<T> { |
85aaf69f SL |
1309 | type Item = T; |
1310 | type IntoIter = IntoIter<T>; | |
1311 | ||
9346a6ac AL |
1312 | /// Creates a consuming iterator, that is, one that moves each value out of |
1313 | /// the binary heap in arbitrary order. The binary heap cannot be used | |
1314 | /// after calling this. | |
1315 | /// | |
1316 | /// # Examples | |
1317 | /// | |
54a0048b SL |
1318 | /// Basic usage: |
1319 | /// | |
9346a6ac | 1320 | /// ``` |
9346a6ac | 1321 | /// use std::collections::BinaryHeap; |
b039eaaf | 1322 | /// let heap = BinaryHeap::from(vec![1, 2, 3, 4]); |
9346a6ac AL |
1323 | /// |
1324 | /// // Print 1, 2, 3, 4 in arbitrary order | |
1325 | /// for x in heap.into_iter() { | |
1326 | /// // x has type i32, not &i32 | |
1327 | /// println!("{}", x); | |
1328 | /// } | |
1329 | /// ``` | |
85aaf69f | 1330 | fn into_iter(self) -> IntoIter<T> { |
9346a6ac | 1331 | IntoIter { iter: self.data.into_iter() } |
85aaf69f SL |
1332 | } |
1333 | } | |
1334 | ||
1335 | #[stable(feature = "rust1", since = "1.0.0")] | |
9fa01778 | 1336 | impl<'a, T> IntoIterator for &'a BinaryHeap<T> { |
85aaf69f SL |
1337 | type Item = &'a T; |
1338 | type IntoIter = Iter<'a, T>; | |
1339 | ||
1340 | fn into_iter(self) -> Iter<'a, T> { | |
1341 | self.iter() | |
1a4d82fc JJ |
1342 | } |
1343 | } | |
1344 | ||
85aaf69f | 1345 | #[stable(feature = "rust1", since = "1.0.0")] |
1a4d82fc | 1346 | impl<T: Ord> Extend<T> for BinaryHeap<T> { |
a7813a04 | 1347 | #[inline] |
54a0048b | 1348 | fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { |
a7813a04 XL |
1349 | <Self as SpecExtend<I>>::spec_extend(self, iter); |
1350 | } | |
1351 | } | |
1352 | ||
1353 | impl<T: Ord, I: IntoIterator<Item = T>> SpecExtend<I> for BinaryHeap<T> { | |
1354 | default fn spec_extend(&mut self, iter: I) { | |
1355 | self.extend_desugared(iter.into_iter()); | |
1356 | } | |
1357 | } | |
1358 | ||
1359 | impl<T: Ord> SpecExtend<BinaryHeap<T>> for BinaryHeap<T> { | |
1360 | fn spec_extend(&mut self, ref mut other: BinaryHeap<T>) { | |
1361 | self.append(other); | |
1362 | } | |
1363 | } | |
1364 | ||
1365 | impl<T: Ord> BinaryHeap<T> { | |
1366 | fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) { | |
54a0048b SL |
1367 | let iterator = iter.into_iter(); |
1368 | let (lower, _) = iterator.size_hint(); | |
1a4d82fc JJ |
1369 | |
1370 | self.reserve(lower); | |
1371 | ||
532ac7d7 | 1372 | iterator.for_each(move |elem| self.push(elem)); |
1a4d82fc JJ |
1373 | } |
1374 | } | |
62682a34 SL |
1375 | |
1376 | #[stable(feature = "extend_ref", since = "1.2.0")] | |
1377 | impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BinaryHeap<T> { | |
92a42be0 | 1378 | fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { |
62682a34 SL |
1379 | self.extend(iter.into_iter().cloned()); |
1380 | } | |
1381 | } |