| //! A priority queue implemented with a binary heap. |
| //! |
| //! Insertion and popping the largest element have *O*(log(*n*)) time complexity. |
| //! Checking the largest element is *O*(1). Converting a vector to a binary heap |
| //! can be done in-place, and has *O*(*n*) complexity. A binary heap can also be |
| //! converted to a sorted vector in-place, allowing it to be used for an *O*(*n* * log(*n*)) |
| //! in-place heapsort. |
| //! |
| //! # Examples |
| //! |
| //! This is a larger example that implements [Dijkstra's algorithm][dijkstra] |
| //! to solve the [shortest path problem][sssp] on a [directed graph][dir_graph]. |
| //! It shows how to use [`BinaryHeap`] with custom types. |
| //! |
| //! [dijkstra]: https://en.wikipedia.org/wiki/Dijkstra%27s_algorithm |
| //! [sssp]: https://en.wikipedia.org/wiki/Shortest_path_problem |
| //! [dir_graph]: https://en.wikipedia.org/wiki/Directed_graph |
| //! |
| //! ``` |
| //! use std::cmp::Ordering; |
| //! use std::collections::BinaryHeap; |
| //! |
| //! #[derive(Copy, Clone, Eq, PartialEq)] |
| //! struct State { |
| //! cost: usize, |
| //! position: usize, |
| //! } |
| //! |
| //! // The priority queue depends on `Ord`. |
| //! // Explicitly implement the trait so the queue becomes a min-heap |
| //! // instead of a max-heap. |
| //! impl Ord for State { |
| //! fn cmp(&self, other: &Self) -> Ordering { |
| //! // Notice that the we flip the ordering on costs. |
| //! // In case of a tie we compare positions - this step is necessary |
| //! // to make implementations of `PartialEq` and `Ord` consistent. |
| //! other.cost.cmp(&self.cost) |
| //! .then_with(|| self.position.cmp(&other.position)) |
| //! } |
| //! } |
| //! |
| //! // `PartialOrd` needs to be implemented as well. |
| //! impl PartialOrd for State { |
| //! fn partial_cmp(&self, other: &Self) -> Option<Ordering> { |
| //! Some(self.cmp(other)) |
| //! } |
| //! } |
| //! |
| //! // Each node is represented as a `usize`, for a shorter implementation. |
| //! struct Edge { |
| //! node: usize, |
| //! cost: usize, |
| //! } |
| //! |
| //! // Dijkstra's shortest path algorithm. |
| //! |
| //! // Start at `start` and use `dist` to track the current shortest distance |
| //! // to each node. This implementation isn't memory-efficient as it may leave duplicate |
| //! // nodes in the queue. It also uses `usize::MAX` as a sentinel value, |
| //! // for a simpler implementation. |
| //! fn shortest_path(adj_list: &Vec<Vec<Edge>>, start: usize, goal: usize) -> Option<usize> { |
| //! // dist[node] = current shortest distance from `start` to `node` |
| //! let mut dist: Vec<_> = (0..adj_list.len()).map(|_| usize::MAX).collect(); |
| //! |
| //! let mut heap = BinaryHeap::new(); |
| //! |
| //! // We're at `start`, with a zero cost |
| //! dist[start] = 0; |
| //! heap.push(State { cost: 0, position: start }); |
| //! |
| //! // Examine the frontier with lower cost nodes first (min-heap) |
| //! while let Some(State { cost, position }) = heap.pop() { |
| //! // Alternatively we could have continued to find all shortest paths |
| //! if position == goal { return Some(cost); } |
| //! |
| //! // Important as we may have already found a better way |
| //! if cost > dist[position] { continue; } |
| //! |
| //! // For each node we can reach, see if we can find a way with |
| //! // a lower cost going through this node |
| //! for edge in &adj_list[position] { |
| //! let next = State { cost: cost + edge.cost, position: edge.node }; |
| //! |
| //! // If so, add it to the frontier and continue |
| //! if next.cost < dist[next.position] { |
| //! heap.push(next); |
| //! // Relaxation, we have now found a better way |
| //! dist[next.position] = next.cost; |
| //! } |
| //! } |
| //! } |
| //! |
| //! // Goal not reachable |
| //! None |
| //! } |
| //! |
| //! fn main() { |
| //! // This is the directed graph we're going to use. |
| //! // The node numbers correspond to the different states, |
| //! // and the edge weights symbolize the cost of moving |
| //! // from one node to another. |
| //! // Note that the edges are one-way. |
| //! // |
| //! // 7 |
| //! // +-----------------+ |
| //! // | | |
| //! // v 1 2 | 2 |
| //! // 0 -----> 1 -----> 3 ---> 4 |
| //! // | ^ ^ ^ |
| //! // | | 1 | | |
| //! // | | | 3 | 1 |
| //! // +------> 2 -------+ | |
| //! // 10 | | |
| //! // +---------------+ |
| //! // |
| //! // The graph is represented as an adjacency list where each index, |
| //! // corresponding to a node value, has a list of outgoing edges. |
| //! // Chosen for its efficiency. |
| //! let graph = vec![ |
| //! // Node 0 |
| //! vec![Edge { node: 2, cost: 10 }, |
| //! Edge { node: 1, cost: 1 }], |
| //! // Node 1 |
| //! vec![Edge { node: 3, cost: 2 }], |
| //! // Node 2 |
| //! vec![Edge { node: 1, cost: 1 }, |
| //! Edge { node: 3, cost: 3 }, |
| //! Edge { node: 4, cost: 1 }], |
| //! // Node 3 |
| //! vec![Edge { node: 0, cost: 7 }, |
| //! Edge { node: 4, cost: 2 }], |
| //! // Node 4 |
| //! vec![]]; |
| //! |
| //! assert_eq!(shortest_path(&graph, 0, 1), Some(1)); |
| //! assert_eq!(shortest_path(&graph, 0, 3), Some(3)); |
| //! assert_eq!(shortest_path(&graph, 3, 0), Some(7)); |
| //! assert_eq!(shortest_path(&graph, 0, 4), Some(5)); |
| //! assert_eq!(shortest_path(&graph, 4, 0), None); |
| //! } |
| //! ``` |
| |
| #![allow(missing_docs)] |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use core::fmt; |
| use core::iter::{FromIterator, FusedIterator, InPlaceIterable, SourceIter, TrustedLen}; |
| use core::mem::{self, swap, ManuallyDrop}; |
| use core::ops::{Deref, DerefMut}; |
| use core::ptr; |
| |
| use crate::collections::TryReserveError; |
| use crate::slice; |
| use crate::vec::{self, AsVecIntoIter, Vec}; |
| |
| use super::SpecExtend; |
| |
| #[cfg(test)] |
| mod tests; |
| |
| /// A priority queue implemented with a binary heap. |
| /// |
| /// This will be a max-heap. |
| /// |
| /// It is a logic error for an item to be modified in such a way that the |
| /// item's ordering relative to any other item, as determined by the [`Ord`] |
| /// trait, changes while it is in the heap. This is normally only possible |
| /// through [`Cell`], [`RefCell`], global state, I/O, or unsafe code. The |
| /// behavior resulting from such a logic error is not specified, but will |
| /// be encapsulated to the `BinaryHeap` that observed the logic error and not |
| /// result in undefined behavior. This could include panics, incorrect results, |
| /// aborts, memory leaks, and non-termination. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// |
| /// // Type inference lets us omit an explicit type signature (which |
| /// // would be `BinaryHeap<i32>` in this example). |
| /// let mut heap = BinaryHeap::new(); |
| /// |
| /// // We can use peek to look at the next item in the heap. In this case, |
| /// // there's no items in there yet so we get None. |
| /// assert_eq!(heap.peek(), None); |
| /// |
| /// // Let's add some scores... |
| /// heap.push(1); |
| /// heap.push(5); |
| /// heap.push(2); |
| /// |
| /// // Now peek shows the most important item in the heap. |
| /// assert_eq!(heap.peek(), Some(&5)); |
| /// |
| /// // We can check the length of a heap. |
| /// assert_eq!(heap.len(), 3); |
| /// |
| /// // We can iterate over the items in the heap, although they are returned in |
| /// // a random order. |
| /// for x in &heap { |
| /// println!("{x}"); |
| /// } |
| /// |
| /// // If we instead pop these scores, they should come back in order. |
| /// assert_eq!(heap.pop(), Some(5)); |
| /// assert_eq!(heap.pop(), Some(2)); |
| /// assert_eq!(heap.pop(), Some(1)); |
| /// assert_eq!(heap.pop(), None); |
| /// |
| /// // We can clear the heap of any remaining items. |
| /// heap.clear(); |
| /// |
| /// // The heap should now be empty. |
| /// assert!(heap.is_empty()) |
| /// ``` |
| /// |
| /// A `BinaryHeap` with a known list of items can be initialized from an array: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let heap = BinaryHeap::from([1, 5, 2]); |
| /// ``` |
| /// |
| /// ## Min-heap |
| /// |
| /// Either [`core::cmp::Reverse`] or a custom [`Ord`] implementation can be used to |
| /// make `BinaryHeap` a min-heap. This makes `heap.pop()` return the smallest |
| /// value instead of the greatest one. |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// use std::cmp::Reverse; |
| /// |
| /// let mut heap = BinaryHeap::new(); |
| /// |
| /// // Wrap values in `Reverse` |
| /// heap.push(Reverse(1)); |
| /// heap.push(Reverse(5)); |
| /// heap.push(Reverse(2)); |
| /// |
| /// // If we pop these scores now, they should come back in the reverse order. |
| /// assert_eq!(heap.pop(), Some(Reverse(1))); |
| /// assert_eq!(heap.pop(), Some(Reverse(2))); |
| /// assert_eq!(heap.pop(), Some(Reverse(5))); |
| /// assert_eq!(heap.pop(), None); |
| /// ``` |
| /// |
| /// # Time complexity |
| /// |
| /// | [push] | [pop] | [peek]/[peek\_mut] | |
| /// |---------|---------------|--------------------| |
| /// | *O*(1)~ | *O*(log(*n*)) | *O*(1) | |
| /// |
| /// The value for `push` is an expected cost; the method documentation gives a |
| /// more detailed analysis. |
| /// |
| /// [`core::cmp::Reverse`]: core::cmp::Reverse |
| /// [`Ord`]: core::cmp::Ord |
| /// [`Cell`]: core::cell::Cell |
| /// [`RefCell`]: core::cell::RefCell |
| /// [push]: BinaryHeap::push |
| /// [pop]: BinaryHeap::pop |
| /// [peek]: BinaryHeap::peek |
| /// [peek\_mut]: BinaryHeap::peek_mut |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[cfg_attr(not(test), rustc_diagnostic_item = "BinaryHeap")] |
| pub struct BinaryHeap<T> { |
| data: Vec<T>, |
| } |
| |
| /// Structure wrapping a mutable reference to the greatest item on a |
| /// `BinaryHeap`. |
| /// |
| /// This `struct` is created by the [`peek_mut`] method on [`BinaryHeap`]. See |
| /// its documentation for more. |
| /// |
| /// [`peek_mut`]: BinaryHeap::peek_mut |
| #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
| pub struct PeekMut<'a, T: 'a + Ord> { |
| heap: &'a mut BinaryHeap<T>, |
| sift: bool, |
| } |
| |
| #[stable(feature = "collection_debug", since = "1.17.0")] |
| impl<T: Ord + fmt::Debug> fmt::Debug for PeekMut<'_, T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_tuple("PeekMut").field(&self.heap.data[0]).finish() |
| } |
| } |
| |
| #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
| impl<T: Ord> Drop for PeekMut<'_, T> { |
| fn drop(&mut self) { |
| if self.sift { |
| // SAFETY: PeekMut is only instantiated for non-empty heaps. |
| unsafe { self.heap.sift_down(0) }; |
| } |
| } |
| } |
| |
| #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
| impl<T: Ord> Deref for PeekMut<'_, T> { |
| type Target = T; |
| fn deref(&self) -> &T { |
| debug_assert!(!self.heap.is_empty()); |
| // SAFE: PeekMut is only instantiated for non-empty heaps |
| unsafe { self.heap.data.get_unchecked(0) } |
| } |
| } |
| |
| #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
| impl<T: Ord> DerefMut for PeekMut<'_, T> { |
| fn deref_mut(&mut self) -> &mut T { |
| debug_assert!(!self.heap.is_empty()); |
| self.sift = true; |
| // SAFE: PeekMut is only instantiated for non-empty heaps |
| unsafe { self.heap.data.get_unchecked_mut(0) } |
| } |
| } |
| |
| impl<'a, T: Ord> PeekMut<'a, T> { |
| /// Removes the peeked value from the heap and returns it. |
| #[stable(feature = "binary_heap_peek_mut_pop", since = "1.18.0")] |
| pub fn pop(mut this: PeekMut<'a, T>) -> T { |
| let value = this.heap.pop().unwrap(); |
| this.sift = false; |
| value |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Clone> Clone for BinaryHeap<T> { |
| fn clone(&self) -> Self { |
| BinaryHeap { data: self.data.clone() } |
| } |
| |
| fn clone_from(&mut self, source: &Self) { |
| self.data.clone_from(&source.data); |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Ord> Default for BinaryHeap<T> { |
| /// Creates an empty `BinaryHeap<T>`. |
| #[inline] |
| fn default() -> BinaryHeap<T> { |
| BinaryHeap::new() |
| } |
| } |
| |
| #[stable(feature = "binaryheap_debug", since = "1.4.0")] |
| impl<T: fmt::Debug> fmt::Debug for BinaryHeap<T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_list().entries(self.iter()).finish() |
| } |
| } |
| |
| impl<T: Ord> BinaryHeap<T> { |
| /// Creates an empty `BinaryHeap` as a max-heap. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// heap.push(4); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[must_use] |
| pub fn new() -> BinaryHeap<T> { |
| BinaryHeap { data: vec![] } |
| } |
| |
| /// Creates an empty `BinaryHeap` with at least the specified capacity. |
| /// |
| /// The binary heap will be able to hold at least `capacity` elements without |
| /// reallocating. This method is allowed to allocate for more elements than |
| /// `capacity`. If `capacity` is 0, the binary heap will not allocate. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::with_capacity(10); |
| /// heap.push(4); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[must_use] |
| pub fn with_capacity(capacity: usize) -> BinaryHeap<T> { |
| BinaryHeap { data: Vec::with_capacity(capacity) } |
| } |
| |
| /// Returns a mutable reference to the greatest item in the binary heap, or |
| /// `None` if it is empty. |
| /// |
| /// Note: If the `PeekMut` value is leaked, the heap may be in an |
| /// inconsistent state. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// assert!(heap.peek_mut().is_none()); |
| /// |
| /// heap.push(1); |
| /// heap.push(5); |
| /// heap.push(2); |
| /// { |
| /// let mut val = heap.peek_mut().unwrap(); |
| /// *val = 0; |
| /// } |
| /// assert_eq!(heap.peek(), Some(&2)); |
| /// ``` |
| /// |
| /// # Time complexity |
| /// |
| /// If the item is modified then the worst case time complexity is *O*(log(*n*)), |
| /// otherwise it's *O*(1). |
| #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")] |
| pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>> { |
| if self.is_empty() { None } else { Some(PeekMut { heap: self, sift: false }) } |
| } |
| |
| /// Removes the greatest item from the binary heap and returns it, or `None` if it |
| /// is empty. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::from([1, 3]); |
| /// |
| /// assert_eq!(heap.pop(), Some(3)); |
| /// assert_eq!(heap.pop(), Some(1)); |
| /// assert_eq!(heap.pop(), None); |
| /// ``` |
| /// |
| /// # Time complexity |
| /// |
| /// The worst case cost of `pop` on a heap containing *n* elements is *O*(log(*n*)). |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn pop(&mut self) -> Option<T> { |
| self.data.pop().map(|mut item| { |
| if !self.is_empty() { |
| swap(&mut item, &mut self.data[0]); |
| // SAFETY: !self.is_empty() means that self.len() > 0 |
| unsafe { self.sift_down_to_bottom(0) }; |
| } |
| item |
| }) |
| } |
| |
| /// Pushes an item onto the binary heap. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// heap.push(3); |
| /// heap.push(5); |
| /// heap.push(1); |
| /// |
| /// assert_eq!(heap.len(), 3); |
| /// assert_eq!(heap.peek(), Some(&5)); |
| /// ``` |
| /// |
| /// # Time complexity |
| /// |
| /// The expected cost of `push`, averaged over every possible ordering of |
| /// the elements being pushed, and over a sufficiently large number of |
| /// pushes, is *O*(1). This is the most meaningful cost metric when pushing |
| /// elements that are *not* already in any sorted pattern. |
| /// |
| /// The time complexity degrades if elements are pushed in predominantly |
| /// ascending order. In the worst case, elements are pushed in ascending |
| /// sorted order and the amortized cost per push is *O*(log(*n*)) against a heap |
| /// containing *n* elements. |
| /// |
| /// The worst case cost of a *single* call to `push` is *O*(*n*). The worst case |
| /// occurs when capacity is exhausted and needs a resize. The resize cost |
| /// has been amortized in the previous figures. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn push(&mut self, item: T) { |
| let old_len = self.len(); |
| self.data.push(item); |
| // SAFETY: Since we pushed a new item it means that |
| // old_len = self.len() - 1 < self.len() |
| unsafe { self.sift_up(0, old_len) }; |
| } |
| |
| /// Consumes the `BinaryHeap` and returns a vector in sorted |
| /// (ascending) order. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let mut heap = BinaryHeap::from([1, 2, 4, 5, 7]); |
| /// heap.push(6); |
| /// heap.push(3); |
| /// |
| /// let vec = heap.into_sorted_vec(); |
| /// assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]); |
| /// ``` |
| #[must_use = "`self` will be dropped if the result is not used"] |
| #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
| pub fn into_sorted_vec(mut self) -> Vec<T> { |
| let mut end = self.len(); |
| while end > 1 { |
| end -= 1; |
| // SAFETY: `end` goes from `self.len() - 1` to 1 (both included), |
| // so it's always a valid index to access. |
| // It is safe to access index 0 (i.e. `ptr`), because |
| // 1 <= end < self.len(), which means self.len() >= 2. |
| unsafe { |
| let ptr = self.data.as_mut_ptr(); |
| ptr::swap(ptr, ptr.add(end)); |
| } |
| // SAFETY: `end` goes from `self.len() - 1` to 1 (both included) so: |
| // 0 < 1 <= end <= self.len() - 1 < self.len() |
| // Which means 0 < end and end < self.len(). |
| unsafe { self.sift_down_range(0, end) }; |
| } |
| self.into_vec() |
| } |
| |
| // The implementations of sift_up and sift_down use unsafe blocks in |
| // order to move an element out of the vector (leaving behind a |
| // hole), shift along the others and move the removed element back into the |
| // vector at the final location of the hole. |
| // The `Hole` type is used to represent this, and make sure |
| // the hole is filled back at the end of its scope, even on panic. |
| // Using a hole reduces the constant factor compared to using swaps, |
| // which involves twice as many moves. |
| |
| /// # Safety |
| /// |
| /// The caller must guarantee that `pos < self.len()`. |
| unsafe fn sift_up(&mut self, start: usize, pos: usize) -> usize { |
| // Take out the value at `pos` and create a hole. |
| // SAFETY: The caller guarantees that pos < self.len() |
| let mut hole = unsafe { Hole::new(&mut self.data, pos) }; |
| |
| while hole.pos() > start { |
| let parent = (hole.pos() - 1) / 2; |
| |
| // SAFETY: hole.pos() > start >= 0, which means hole.pos() > 0 |
| // and so hole.pos() - 1 can't underflow. |
| // This guarantees that parent < hole.pos() so |
| // it's a valid index and also != hole.pos(). |
| if hole.element() <= unsafe { hole.get(parent) } { |
| break; |
| } |
| |
| // SAFETY: Same as above |
| unsafe { hole.move_to(parent) }; |
| } |
| |
| hole.pos() |
| } |
| |
| /// Take an element at `pos` and move it down the heap, |
| /// while its children are larger. |
| /// |
| /// # Safety |
| /// |
| /// The caller must guarantee that `pos < end <= self.len()`. |
| unsafe fn sift_down_range(&mut self, pos: usize, end: usize) { |
| // SAFETY: The caller guarantees that pos < end <= self.len(). |
| let mut hole = unsafe { Hole::new(&mut self.data, pos) }; |
| let mut child = 2 * hole.pos() + 1; |
| |
| // Loop invariant: child == 2 * hole.pos() + 1. |
| while child <= end.saturating_sub(2) { |
| // compare with the greater of the two children |
| // SAFETY: child < end - 1 < self.len() and |
| // child + 1 < end <= self.len(), so they're valid indexes. |
| // child == 2 * hole.pos() + 1 != hole.pos() and |
| // child + 1 == 2 * hole.pos() + 2 != hole.pos(). |
| // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow |
| // if T is a ZST |
| child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize; |
| |
| // if we are already in order, stop. |
| // SAFETY: child is now either the old child or the old child+1 |
| // We already proven that both are < self.len() and != hole.pos() |
| if hole.element() >= unsafe { hole.get(child) } { |
| return; |
| } |
| |
| // SAFETY: same as above. |
| unsafe { hole.move_to(child) }; |
| child = 2 * hole.pos() + 1; |
| } |
| |
| // SAFETY: && short circuit, which means that in the |
| // second condition it's already true that child == end - 1 < self.len(). |
| if child == end - 1 && hole.element() < unsafe { hole.get(child) } { |
| // SAFETY: child is already proven to be a valid index and |
| // child == 2 * hole.pos() + 1 != hole.pos(). |
| unsafe { hole.move_to(child) }; |
| } |
| } |
| |
| /// # Safety |
| /// |
| /// The caller must guarantee that `pos < self.len()`. |
| unsafe fn sift_down(&mut self, pos: usize) { |
| let len = self.len(); |
| // SAFETY: pos < len is guaranteed by the caller and |
| // obviously len = self.len() <= self.len(). |
| unsafe { self.sift_down_range(pos, len) }; |
| } |
| |
| /// Take an element at `pos` and move it all the way down the heap, |
| /// then sift it up to its position. |
| /// |
| /// Note: This is faster when the element is known to be large / should |
| /// be closer to the bottom. |
| /// |
| /// # Safety |
| /// |
| /// The caller must guarantee that `pos < self.len()`. |
| unsafe fn sift_down_to_bottom(&mut self, mut pos: usize) { |
| let end = self.len(); |
| let start = pos; |
| |
| // SAFETY: The caller guarantees that pos < self.len(). |
| let mut hole = unsafe { Hole::new(&mut self.data, pos) }; |
| let mut child = 2 * hole.pos() + 1; |
| |
| // Loop invariant: child == 2 * hole.pos() + 1. |
| while child <= end.saturating_sub(2) { |
| // SAFETY: child < end - 1 < self.len() and |
| // child + 1 < end <= self.len(), so they're valid indexes. |
| // child == 2 * hole.pos() + 1 != hole.pos() and |
| // child + 1 == 2 * hole.pos() + 2 != hole.pos(). |
| // FIXME: 2 * hole.pos() + 1 or 2 * hole.pos() + 2 could overflow |
| // if T is a ZST |
| child += unsafe { hole.get(child) <= hole.get(child + 1) } as usize; |
| |
| // SAFETY: Same as above |
| unsafe { hole.move_to(child) }; |
| child = 2 * hole.pos() + 1; |
| } |
| |
| if child == end - 1 { |
| // SAFETY: child == end - 1 < self.len(), so it's a valid index |
| // and child == 2 * hole.pos() + 1 != hole.pos(). |
| unsafe { hole.move_to(child) }; |
| } |
| pos = hole.pos(); |
| drop(hole); |
| |
| // SAFETY: pos is the position in the hole and was already proven |
| // to be a valid index. |
| unsafe { self.sift_up(start, pos) }; |
| } |
| |
| /// Rebuild assuming data[0..start] is still a proper heap. |
| fn rebuild_tail(&mut self, start: usize) { |
| if start == self.len() { |
| return; |
| } |
| |
| let tail_len = self.len() - start; |
| |
| #[inline(always)] |
| fn log2_fast(x: usize) -> usize { |
| (usize::BITS - x.leading_zeros() - 1) as usize |
| } |
| |
| // `rebuild` takes O(self.len()) operations |
| // and about 2 * self.len() comparisons in the worst case |
| // while repeating `sift_up` takes O(tail_len * log(start)) operations |
| // and about 1 * tail_len * log_2(start) comparisons in the worst case, |
| // assuming start >= tail_len. For larger heaps, the crossover point |
| // no longer follows this reasoning and was determined empirically. |
| let better_to_rebuild = if start < tail_len { |
| true |
| } else if self.len() <= 2048 { |
| 2 * self.len() < tail_len * log2_fast(start) |
| } else { |
| 2 * self.len() < tail_len * 11 |
| }; |
| |
| if better_to_rebuild { |
| self.rebuild(); |
| } else { |
| for i in start..self.len() { |
| // SAFETY: The index `i` is always less than self.len(). |
| unsafe { self.sift_up(0, i) }; |
| } |
| } |
| } |
| |
| fn rebuild(&mut self) { |
| let mut n = self.len() / 2; |
| while n > 0 { |
| n -= 1; |
| // SAFETY: n starts from self.len() / 2 and goes down to 0. |
| // The only case when !(n < self.len()) is if |
| // self.len() == 0, but it's ruled out by the loop condition. |
| unsafe { self.sift_down(n) }; |
| } |
| } |
| |
| /// Moves all the elements of `other` into `self`, leaving `other` empty. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let mut a = BinaryHeap::from([-10, 1, 2, 3, 3]); |
| /// let mut b = BinaryHeap::from([-20, 5, 43]); |
| /// |
| /// a.append(&mut b); |
| /// |
| /// assert_eq!(a.into_sorted_vec(), [-20, -10, 1, 2, 3, 3, 5, 43]); |
| /// assert!(b.is_empty()); |
| /// ``` |
| #[stable(feature = "binary_heap_append", since = "1.11.0")] |
| pub fn append(&mut self, other: &mut Self) { |
| if self.len() < other.len() { |
| swap(self, other); |
| } |
| |
| let start = self.data.len(); |
| |
| self.data.append(&mut other.data); |
| |
| self.rebuild_tail(start); |
| } |
| |
| /// Clears the binary heap, returning an iterator over the removed elements |
| /// in heap order. If the iterator is dropped before being fully consumed, |
| /// it drops the remaining elements in heap order. |
| /// |
| /// The returned iterator keeps a mutable borrow on the heap to optimize |
| /// its implementation. |
| /// |
| /// Note: |
| /// * `.drain_sorted()` is *O*(*n* \* log(*n*)); much slower than `.drain()`. |
| /// You should use the latter for most cases. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// #![feature(binary_heap_drain_sorted)] |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let mut heap = BinaryHeap::from([1, 2, 3, 4, 5]); |
| /// assert_eq!(heap.len(), 5); |
| /// |
| /// drop(heap.drain_sorted()); // removes all elements in heap order |
| /// assert_eq!(heap.len(), 0); |
| /// ``` |
| #[inline] |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| pub fn drain_sorted(&mut self) -> DrainSorted<'_, T> { |
| DrainSorted { inner: self } |
| } |
| |
| /// Retains only the elements specified by the predicate. |
| /// |
| /// In other words, remove all elements `e` for which `f(&e)` returns |
| /// `false`. The elements are visited in unsorted (and unspecified) order. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// #![feature(binary_heap_retain)] |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let mut heap = BinaryHeap::from([-10, -5, 1, 2, 4, 13]); |
| /// |
| /// heap.retain(|x| x % 2 == 0); // only keep even numbers |
| /// |
| /// assert_eq!(heap.into_sorted_vec(), [-10, 2, 4]) |
| /// ``` |
| #[unstable(feature = "binary_heap_retain", issue = "71503")] |
| pub fn retain<F>(&mut self, mut f: F) |
| where |
| F: FnMut(&T) -> bool, |
| { |
| let mut first_removed = self.len(); |
| let mut i = 0; |
| self.data.retain(|e| { |
| let keep = f(e); |
| if !keep && i < first_removed { |
| first_removed = i; |
| } |
| i += 1; |
| keep |
| }); |
| // data[0..first_removed] is untouched, so we only need to rebuild the tail: |
| self.rebuild_tail(first_removed); |
| } |
| } |
| |
| impl<T> BinaryHeap<T> { |
| /// Returns an iterator visiting all values in the underlying vector, in |
| /// arbitrary order. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let heap = BinaryHeap::from([1, 2, 3, 4]); |
| /// |
| /// // Print 1, 2, 3, 4 in arbitrary order |
| /// for x in heap.iter() { |
| /// println!("{x}"); |
| /// } |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn iter(&self) -> Iter<'_, T> { |
| Iter { iter: self.data.iter() } |
| } |
| |
| /// Returns an iterator which retrieves elements in heap order. |
| /// This method consumes the original heap. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// #![feature(binary_heap_into_iter_sorted)] |
| /// use std::collections::BinaryHeap; |
| /// let heap = BinaryHeap::from([1, 2, 3, 4, 5]); |
| /// |
| /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), [5, 4]); |
| /// ``` |
| #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
| pub fn into_iter_sorted(self) -> IntoIterSorted<T> { |
| IntoIterSorted { inner: self } |
| } |
| |
| /// Returns the greatest item in the binary heap, or `None` if it is empty. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// assert_eq!(heap.peek(), None); |
| /// |
| /// heap.push(1); |
| /// heap.push(5); |
| /// heap.push(2); |
| /// assert_eq!(heap.peek(), Some(&5)); |
| /// |
| /// ``` |
| /// |
| /// # Time complexity |
| /// |
| /// Cost is *O*(1) in the worst case. |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn peek(&self) -> Option<&T> { |
| self.data.get(0) |
| } |
| |
| /// Returns the number of elements the binary heap can hold without reallocating. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::with_capacity(100); |
| /// assert!(heap.capacity() >= 100); |
| /// heap.push(4); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn capacity(&self) -> usize { |
| self.data.capacity() |
| } |
| |
| /// Reserves the minimum capacity for at least `additional` elements more than |
| /// the current length. Unlike [`reserve`], this will not |
| /// deliberately over-allocate to speculatively avoid frequent allocations. |
| /// After calling `reserve_exact`, capacity will be greater than or equal to |
| /// `self.len() + additional`. Does nothing if the capacity is already |
| /// sufficient. |
| /// |
| /// [`reserve`]: BinaryHeap::reserve |
| /// |
| /// # Panics |
| /// |
| /// Panics if the new capacity overflows [`usize`]. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// heap.reserve_exact(100); |
| /// assert!(heap.capacity() >= 100); |
| /// heap.push(4); |
| /// ``` |
| /// |
| /// [`reserve`]: BinaryHeap::reserve |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn reserve_exact(&mut self, additional: usize) { |
| self.data.reserve_exact(additional); |
| } |
| |
| /// Reserves capacity for at least `additional` elements more than the |
| /// current length. The allocator may reserve more space to speculatively |
| /// avoid frequent allocations. After calling `reserve`, |
| /// capacity will be greater than or equal to `self.len() + additional`. |
| /// Does nothing if capacity is already sufficient. |
| /// |
| /// # Panics |
| /// |
| /// Panics if the new capacity overflows [`usize`]. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// heap.reserve(100); |
| /// assert!(heap.capacity() >= 100); |
| /// heap.push(4); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn reserve(&mut self, additional: usize) { |
| self.data.reserve(additional); |
| } |
| |
| /// Tries to reserve the minimum capacity for at least `additional` elements |
| /// more than the current length. Unlike [`try_reserve`], this will not |
| /// deliberately over-allocate to speculatively avoid frequent allocations. |
| /// After calling `try_reserve_exact`, capacity will be greater than or |
| /// equal to `self.len() + additional` if it returns `Ok(())`. |
| /// Does nothing if the capacity is already sufficient. |
| /// |
| /// Note that the allocator may give the collection more space than it |
| /// requests. Therefore, capacity can not be relied upon to be precisely |
| /// minimal. Prefer [`try_reserve`] if future insertions are expected. |
| /// |
| /// [`try_reserve`]: BinaryHeap::try_reserve |
| /// |
| /// # Errors |
| /// |
| /// If the capacity overflows, or the allocator reports a failure, then an error |
| /// is returned. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// use std::collections::TryReserveError; |
| /// |
| /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> { |
| /// let mut heap = BinaryHeap::new(); |
| /// |
| /// // Pre-reserve the memory, exiting if we can't |
| /// heap.try_reserve_exact(data.len())?; |
| /// |
| /// // Now we know this can't OOM in the middle of our complex work |
| /// heap.extend(data.iter()); |
| /// |
| /// Ok(heap.pop()) |
| /// } |
| /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); |
| /// ``` |
| #[stable(feature = "try_reserve_2", since = "1.63.0")] |
| pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { |
| self.data.try_reserve_exact(additional) |
| } |
| |
| /// Tries to reserve capacity for at least `additional` elements more than the |
| /// current length. The allocator may reserve more space to speculatively |
| /// avoid frequent allocations. After calling `try_reserve`, capacity will be |
| /// greater than or equal to `self.len() + additional` if it returns |
| /// `Ok(())`. Does nothing if capacity is already sufficient. This method |
| /// preserves the contents even if an error occurs. |
| /// |
| /// # Errors |
| /// |
| /// If the capacity overflows, or the allocator reports a failure, then an error |
| /// is returned. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// use std::collections::TryReserveError; |
| /// |
| /// fn find_max_slow(data: &[u32]) -> Result<Option<u32>, TryReserveError> { |
| /// let mut heap = BinaryHeap::new(); |
| /// |
| /// // Pre-reserve the memory, exiting if we can't |
| /// heap.try_reserve(data.len())?; |
| /// |
| /// // Now we know this can't OOM in the middle of our complex work |
| /// heap.extend(data.iter()); |
| /// |
| /// Ok(heap.pop()) |
| /// } |
| /// # find_max_slow(&[1, 2, 3]).expect("why is the test harness OOMing on 12 bytes?"); |
| /// ``` |
| #[stable(feature = "try_reserve_2", since = "1.63.0")] |
| pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { |
| self.data.try_reserve(additional) |
| } |
| |
| /// Discards as much additional capacity as possible. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); |
| /// |
| /// assert!(heap.capacity() >= 100); |
| /// heap.shrink_to_fit(); |
| /// assert!(heap.capacity() == 0); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn shrink_to_fit(&mut self) { |
| self.data.shrink_to_fit(); |
| } |
| |
| /// Discards capacity with a lower bound. |
| /// |
| /// The capacity will remain at least as large as both the length |
| /// and the supplied value. |
| /// |
| /// If the current capacity is less than the lower limit, this is a no-op. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap: BinaryHeap<i32> = BinaryHeap::with_capacity(100); |
| /// |
| /// assert!(heap.capacity() >= 100); |
| /// heap.shrink_to(10); |
| /// assert!(heap.capacity() >= 10); |
| /// ``` |
| #[inline] |
| #[stable(feature = "shrink_to", since = "1.56.0")] |
| pub fn shrink_to(&mut self, min_capacity: usize) { |
| self.data.shrink_to(min_capacity) |
| } |
| |
| /// Returns a slice of all values in the underlying vector, in arbitrary |
| /// order. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// #![feature(binary_heap_as_slice)] |
| /// use std::collections::BinaryHeap; |
| /// use std::io::{self, Write}; |
| /// |
| /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]); |
| /// |
| /// io::sink().write(heap.as_slice()).unwrap(); |
| /// ``` |
| #[must_use] |
| #[unstable(feature = "binary_heap_as_slice", issue = "83659")] |
| pub fn as_slice(&self) -> &[T] { |
| self.data.as_slice() |
| } |
| |
| /// Consumes the `BinaryHeap` and returns the underlying vector |
| /// in arbitrary order. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]); |
| /// let vec = heap.into_vec(); |
| /// |
| /// // Will print in some order |
| /// for x in vec { |
| /// println!("{x}"); |
| /// } |
| /// ``` |
| #[must_use = "`self` will be dropped if the result is not used"] |
| #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
| pub fn into_vec(self) -> Vec<T> { |
| self.into() |
| } |
| |
| /// Returns the length of the binary heap. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let heap = BinaryHeap::from([1, 3]); |
| /// |
| /// assert_eq!(heap.len(), 2); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn len(&self) -> usize { |
| self.data.len() |
| } |
| |
| /// Checks if the binary heap is empty. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::new(); |
| /// |
| /// assert!(heap.is_empty()); |
| /// |
| /// heap.push(3); |
| /// heap.push(5); |
| /// heap.push(1); |
| /// |
| /// assert!(!heap.is_empty()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn is_empty(&self) -> bool { |
| self.len() == 0 |
| } |
| |
| /// Clears the binary heap, returning an iterator over the removed elements |
| /// in arbitrary order. If the iterator is dropped before being fully |
| /// consumed, it drops the remaining elements in arbitrary order. |
| /// |
| /// The returned iterator keeps a mutable borrow on the heap to optimize |
| /// its implementation. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::from([1, 3]); |
| /// |
| /// assert!(!heap.is_empty()); |
| /// |
| /// for x in heap.drain() { |
| /// println!("{x}"); |
| /// } |
| /// |
| /// assert!(heap.is_empty()); |
| /// ``` |
| #[inline] |
| #[stable(feature = "drain", since = "1.6.0")] |
| pub fn drain(&mut self) -> Drain<'_, T> { |
| Drain { iter: self.data.drain(..) } |
| } |
| |
| /// Drops all items from the binary heap. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let mut heap = BinaryHeap::from([1, 3]); |
| /// |
| /// assert!(!heap.is_empty()); |
| /// |
| /// heap.clear(); |
| /// |
| /// assert!(heap.is_empty()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn clear(&mut self) { |
| self.drain(); |
| } |
| } |
| |
| /// Hole represents a hole in a slice i.e., an index without valid value |
| /// (because it was moved from or duplicated). |
| /// In drop, `Hole` will restore the slice by filling the hole |
| /// position with the value that was originally removed. |
| struct Hole<'a, T: 'a> { |
| data: &'a mut [T], |
| elt: ManuallyDrop<T>, |
| pos: usize, |
| } |
| |
| impl<'a, T> Hole<'a, T> { |
| /// Create a new `Hole` at index `pos`. |
| /// |
| /// Unsafe because pos must be within the data slice. |
| #[inline] |
| unsafe fn new(data: &'a mut [T], pos: usize) -> Self { |
| debug_assert!(pos < data.len()); |
| // SAFE: pos should be inside the slice |
| let elt = unsafe { ptr::read(data.get_unchecked(pos)) }; |
| Hole { data, elt: ManuallyDrop::new(elt), pos } |
| } |
| |
| #[inline] |
| fn pos(&self) -> usize { |
| self.pos |
| } |
| |
| /// Returns a reference to the element removed. |
| #[inline] |
| fn element(&self) -> &T { |
| &self.elt |
| } |
| |
| /// Returns a reference to the element at `index`. |
| /// |
| /// Unsafe because index must be within the data slice and not equal to pos. |
| #[inline] |
| unsafe fn get(&self, index: usize) -> &T { |
| debug_assert!(index != self.pos); |
| debug_assert!(index < self.data.len()); |
| unsafe { self.data.get_unchecked(index) } |
| } |
| |
| /// Move hole to new location |
| /// |
| /// Unsafe because index must be within the data slice and not equal to pos. |
| #[inline] |
| unsafe fn move_to(&mut self, index: usize) { |
| debug_assert!(index != self.pos); |
| debug_assert!(index < self.data.len()); |
| unsafe { |
| let ptr = self.data.as_mut_ptr(); |
| let index_ptr: *const _ = ptr.add(index); |
| let hole_ptr = ptr.add(self.pos); |
| ptr::copy_nonoverlapping(index_ptr, hole_ptr, 1); |
| } |
| self.pos = index; |
| } |
| } |
| |
| impl<T> Drop for Hole<'_, T> { |
| #[inline] |
| fn drop(&mut self) { |
| // fill the hole again |
| unsafe { |
| let pos = self.pos; |
| ptr::copy_nonoverlapping(&*self.elt, self.data.get_unchecked_mut(pos), 1); |
| } |
| } |
| } |
| |
| /// An iterator over the elements of a `BinaryHeap`. |
| /// |
| /// This `struct` is created by [`BinaryHeap::iter()`]. See its |
| /// documentation for more. |
| /// |
| /// [`iter`]: BinaryHeap::iter |
| #[must_use = "iterators are lazy and do nothing unless consumed"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub struct Iter<'a, T: 'a> { |
| iter: slice::Iter<'a, T>, |
| } |
| |
| #[stable(feature = "collection_debug", since = "1.17.0")] |
| impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_tuple("Iter").field(&self.iter.as_slice()).finish() |
| } |
| } |
| |
| // FIXME(#26925) Remove in favor of `#[derive(Clone)]` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> Clone for Iter<'_, T> { |
| fn clone(&self) -> Self { |
| Iter { iter: self.iter.clone() } |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, T> Iterator for Iter<'a, T> { |
| type Item = &'a T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<&'a T> { |
| self.iter.next() |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.iter.size_hint() |
| } |
| |
| #[inline] |
| fn last(self) -> Option<&'a T> { |
| self.iter.last() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, T> DoubleEndedIterator for Iter<'a, T> { |
| #[inline] |
| fn next_back(&mut self) -> Option<&'a T> { |
| self.iter.next_back() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> ExactSizeIterator for Iter<'_, T> { |
| fn is_empty(&self) -> bool { |
| self.iter.is_empty() |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<T> FusedIterator for Iter<'_, T> {} |
| |
| /// An owning iterator over the elements of a `BinaryHeap`. |
| /// |
| /// This `struct` is created by [`BinaryHeap::into_iter()`] |
| /// (provided by the [`IntoIterator`] trait). See its documentation for more. |
| /// |
| /// [`into_iter`]: BinaryHeap::into_iter |
| /// [`IntoIterator`]: core::iter::IntoIterator |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[derive(Clone)] |
| pub struct IntoIter<T> { |
| iter: vec::IntoIter<T>, |
| } |
| |
| #[stable(feature = "collection_debug", since = "1.17.0")] |
| impl<T: fmt::Debug> fmt::Debug for IntoIter<T> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| f.debug_tuple("IntoIter").field(&self.iter.as_slice()).finish() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> Iterator for IntoIter<T> { |
| type Item = T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<T> { |
| self.iter.next() |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.iter.size_hint() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> DoubleEndedIterator for IntoIter<T> { |
| #[inline] |
| fn next_back(&mut self) -> Option<T> { |
| self.iter.next_back() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> ExactSizeIterator for IntoIter<T> { |
| fn is_empty(&self) -> bool { |
| self.iter.is_empty() |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<T> FusedIterator for IntoIter<T> {} |
| |
| // In addition to the SAFETY invariants of the following three unsafe traits |
| // also refer to the vec::in_place_collect module documentation to get an overview |
| #[unstable(issue = "none", feature = "inplace_iteration")] |
| #[doc(hidden)] |
| unsafe impl<T> SourceIter for IntoIter<T> { |
| type Source = IntoIter<T>; |
| |
| #[inline] |
| unsafe fn as_inner(&mut self) -> &mut Self::Source { |
| self |
| } |
| } |
| |
| #[unstable(issue = "none", feature = "inplace_iteration")] |
| #[doc(hidden)] |
| unsafe impl<I> InPlaceIterable for IntoIter<I> {} |
| |
| unsafe impl<I> AsVecIntoIter for IntoIter<I> { |
| type Item = I; |
| |
| fn as_into_iter(&mut self) -> &mut vec::IntoIter<Self::Item> { |
| &mut self.iter |
| } |
| } |
| |
| #[must_use = "iterators are lazy and do nothing unless consumed"] |
| #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
| #[derive(Clone, Debug)] |
| pub struct IntoIterSorted<T> { |
| inner: BinaryHeap<T>, |
| } |
| |
| #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
| impl<T: Ord> Iterator for IntoIterSorted<T> { |
| type Item = T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<T> { |
| self.inner.pop() |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let exact = self.inner.len(); |
| (exact, Some(exact)) |
| } |
| } |
| |
| #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
| impl<T: Ord> ExactSizeIterator for IntoIterSorted<T> {} |
| |
| #[unstable(feature = "binary_heap_into_iter_sorted", issue = "59278")] |
| impl<T: Ord> FusedIterator for IntoIterSorted<T> {} |
| |
| #[unstable(feature = "trusted_len", issue = "37572")] |
| unsafe impl<T: Ord> TrustedLen for IntoIterSorted<T> {} |
| |
| /// A draining iterator over the elements of a `BinaryHeap`. |
| /// |
| /// This `struct` is created by [`BinaryHeap::drain()`]. See its |
| /// documentation for more. |
| /// |
| /// [`drain`]: BinaryHeap::drain |
| #[stable(feature = "drain", since = "1.6.0")] |
| #[derive(Debug)] |
| pub struct Drain<'a, T: 'a> { |
| iter: vec::Drain<'a, T>, |
| } |
| |
| #[stable(feature = "drain", since = "1.6.0")] |
| impl<T> Iterator for Drain<'_, T> { |
| type Item = T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<T> { |
| self.iter.next() |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.iter.size_hint() |
| } |
| } |
| |
| #[stable(feature = "drain", since = "1.6.0")] |
| impl<T> DoubleEndedIterator for Drain<'_, T> { |
| #[inline] |
| fn next_back(&mut self) -> Option<T> { |
| self.iter.next_back() |
| } |
| } |
| |
| #[stable(feature = "drain", since = "1.6.0")] |
| impl<T> ExactSizeIterator for Drain<'_, T> { |
| fn is_empty(&self) -> bool { |
| self.iter.is_empty() |
| } |
| } |
| |
| #[stable(feature = "fused", since = "1.26.0")] |
| impl<T> FusedIterator for Drain<'_, T> {} |
| |
| /// A draining iterator over the elements of a `BinaryHeap`. |
| /// |
| /// This `struct` is created by [`BinaryHeap::drain_sorted()`]. See its |
| /// documentation for more. |
| /// |
| /// [`drain_sorted`]: BinaryHeap::drain_sorted |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| #[derive(Debug)] |
| pub struct DrainSorted<'a, T: Ord> { |
| inner: &'a mut BinaryHeap<T>, |
| } |
| |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| impl<'a, T: Ord> Drop for DrainSorted<'a, T> { |
| /// Removes heap elements in heap order. |
| fn drop(&mut self) { |
| struct DropGuard<'r, 'a, T: Ord>(&'r mut DrainSorted<'a, T>); |
| |
| impl<'r, 'a, T: Ord> Drop for DropGuard<'r, 'a, T> { |
| fn drop(&mut self) { |
| while self.0.inner.pop().is_some() {} |
| } |
| } |
| |
| while let Some(item) = self.inner.pop() { |
| let guard = DropGuard(self); |
| drop(item); |
| mem::forget(guard); |
| } |
| } |
| } |
| |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| impl<T: Ord> Iterator for DrainSorted<'_, T> { |
| type Item = T; |
| |
| #[inline] |
| fn next(&mut self) -> Option<T> { |
| self.inner.pop() |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let exact = self.inner.len(); |
| (exact, Some(exact)) |
| } |
| } |
| |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| impl<T: Ord> ExactSizeIterator for DrainSorted<'_, T> {} |
| |
| #[unstable(feature = "binary_heap_drain_sorted", issue = "59278")] |
| impl<T: Ord> FusedIterator for DrainSorted<'_, T> {} |
| |
| #[unstable(feature = "trusted_len", issue = "37572")] |
| unsafe impl<T: Ord> TrustedLen for DrainSorted<'_, T> {} |
| |
| #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
| impl<T: Ord> From<Vec<T>> for BinaryHeap<T> { |
| /// Converts a `Vec<T>` into a `BinaryHeap<T>`. |
| /// |
| /// This conversion happens in-place, and has *O*(*n*) time complexity. |
| fn from(vec: Vec<T>) -> BinaryHeap<T> { |
| let mut heap = BinaryHeap { data: vec }; |
| heap.rebuild(); |
| heap |
| } |
| } |
| |
| #[stable(feature = "std_collections_from_array", since = "1.56.0")] |
| impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T> { |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// |
| /// let mut h1 = BinaryHeap::from([1, 4, 2, 3]); |
| /// let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into(); |
| /// while let Some((a, b)) = h1.pop().zip(h2.pop()) { |
| /// assert_eq!(a, b); |
| /// } |
| /// ``` |
| fn from(arr: [T; N]) -> Self { |
| Self::from_iter(arr) |
| } |
| } |
| |
| #[stable(feature = "binary_heap_extras_15", since = "1.5.0")] |
| impl<T> From<BinaryHeap<T>> for Vec<T> { |
| /// Converts a `BinaryHeap<T>` into a `Vec<T>`. |
| /// |
| /// This conversion requires no data movement or allocation, and has |
| /// constant time complexity. |
| fn from(heap: BinaryHeap<T>) -> Vec<T> { |
| heap.data |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Ord> FromIterator<T> for BinaryHeap<T> { |
| fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> BinaryHeap<T> { |
| BinaryHeap::from(iter.into_iter().collect::<Vec<_>>()) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T> IntoIterator for BinaryHeap<T> { |
| type Item = T; |
| type IntoIter = IntoIter<T>; |
| |
| /// Creates a consuming iterator, that is, one that moves each value out of |
| /// the binary heap in arbitrary order. The binary heap cannot be used |
| /// after calling this. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::collections::BinaryHeap; |
| /// let heap = BinaryHeap::from([1, 2, 3, 4]); |
| /// |
| /// // Print 1, 2, 3, 4 in arbitrary order |
| /// for x in heap.into_iter() { |
| /// // x has type i32, not &i32 |
| /// println!("{x}"); |
| /// } |
| /// ``` |
| fn into_iter(self) -> IntoIter<T> { |
| IntoIter { iter: self.data.into_iter() } |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, T> IntoIterator for &'a BinaryHeap<T> { |
| type Item = &'a T; |
| type IntoIter = Iter<'a, T>; |
| |
| fn into_iter(self) -> Iter<'a, T> { |
| self.iter() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Ord> Extend<T> for BinaryHeap<T> { |
| #[inline] |
| fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) { |
| <Self as SpecExtend<I>>::spec_extend(self, iter); |
| } |
| |
| #[inline] |
| fn extend_one(&mut self, item: T) { |
| self.push(item); |
| } |
| |
| #[inline] |
| fn extend_reserve(&mut self, additional: usize) { |
| self.reserve(additional); |
| } |
| } |
| |
| impl<T: Ord, I: IntoIterator<Item = T>> SpecExtend<I> for BinaryHeap<T> { |
| default fn spec_extend(&mut self, iter: I) { |
| self.extend_desugared(iter.into_iter()); |
| } |
| } |
| |
| impl<T: Ord> SpecExtend<Vec<T>> for BinaryHeap<T> { |
| fn spec_extend(&mut self, ref mut other: Vec<T>) { |
| let start = self.data.len(); |
| self.data.append(other); |
| self.rebuild_tail(start); |
| } |
| } |
| |
| impl<T: Ord> SpecExtend<BinaryHeap<T>> for BinaryHeap<T> { |
| fn spec_extend(&mut self, ref mut other: BinaryHeap<T>) { |
| self.append(other); |
| } |
| } |
| |
| impl<T: Ord> BinaryHeap<T> { |
| fn extend_desugared<I: IntoIterator<Item = T>>(&mut self, iter: I) { |
| let iterator = iter.into_iter(); |
| let (lower, _) = iterator.size_hint(); |
| |
| self.reserve(lower); |
| |
| iterator.for_each(move |elem| self.push(elem)); |
| } |
| } |
| |
| #[stable(feature = "extend_ref", since = "1.2.0")] |
| impl<'a, T: 'a + Ord + Copy> Extend<&'a T> for BinaryHeap<T> { |
| fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) { |
| self.extend(iter.into_iter().cloned()); |
| } |
| |
| #[inline] |
| fn extend_one(&mut self, &item: &'a T) { |
| self.push(item); |
| } |
| |
| #[inline] |
| fn extend_reserve(&mut self, additional: usize) { |
| self.reserve(additional); |
| } |
| } |