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Diffstat (limited to 'src/liballoc/collections/binary_heap.rs')
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diff --git a/src/liballoc/collections/binary_heap.rs b/src/liballoc/collections/binary_heap.rs deleted file mode 100644 index 8398cfa3bd3..00000000000 --- a/src/liballoc/collections/binary_heap.rs +++ /dev/null @@ -1,1431 +0,0 @@ -//! 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]: http://en.wikipedia.org/wiki/Dijkstra%27s_algorithm -//! [sssp]: http://en.wikipedia.org/wiki/Shortest_path_problem -//! [dir_graph]: http://en.wikipedia.org/wiki/Directed_graph -//! [`BinaryHeap`]: struct.BinaryHeap.html -//! -//! ``` -//! 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: &State) -> 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: &State) -> Option<Ordering> { -//! Some(self.cmp(other)) -//! } -//! } -//! -//! // Each node is represented as an `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, TrustedLen}; -use core::mem::{self, size_of, swap, ManuallyDrop}; -use core::ops::{Deref, DerefMut}; -use core::ptr; - -use crate::slice; -use crate::vec::{self, Vec}; - -use super::SpecExtend; - -/// 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. -/// -/// # 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()) -/// ``` -/// -/// ## Min-heap -/// -/// Either `std::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. -/// -/// [push]: #method.push -/// [pop]: #method.pop -/// [peek]: #method.peek -/// [peek\_mut]: #method.peek_mut -#[stable(feature = "rust1", since = "1.0.0")] -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`]: struct.BinaryHeap.html#method.peek_mut -/// [`BinaryHeap`]: struct.BinaryHeap.html -#[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 { - 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()); - // 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")] - pub fn new() -> BinaryHeap<T> { - BinaryHeap { data: vec![] } - } - - /// Creates an empty `BinaryHeap` with a specific capacity. - /// This preallocates enough memory for `capacity` elements, - /// so that the `BinaryHeap` does not have to be reallocated - /// until it contains at least that many values. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// use std::collections::BinaryHeap; - /// let mut heap = BinaryHeap::with_capacity(10); - /// heap.push(4); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - 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 - /// - /// Cost is *O*(1) in the worst case. - #[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: true }) } - } - - /// 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(vec![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]); - 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); - 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(vec![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]); - /// ``` - #[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; - self.data.swap(0, end); - 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. - fn sift_up(&mut self, start: usize, pos: usize) -> usize { - unsafe { - // Take out the value at `pos` and create a hole. - let mut hole = Hole::new(&mut self.data, pos); - - while hole.pos() > start { - let parent = (hole.pos() - 1) / 2; - if hole.element() <= hole.get(parent) { - break; - } - hole.move_to(parent); - } - hole.pos() - } - } - - /// Take an element at `pos` and move it down the heap, - /// while its children are larger. - fn sift_down_range(&mut self, pos: usize, end: usize) { - unsafe { - let mut hole = Hole::new(&mut self.data, pos); - let mut child = 2 * pos + 1; - while child < end { - let right = child + 1; - // compare with the greater of the two children - if right < end && hole.get(child) <= hole.get(right) { - child = right; - } - // if we are already in order, stop. - if hole.element() >= hole.get(child) { - break; - } - hole.move_to(child); - child = 2 * hole.pos() + 1; - } - } - } - - fn sift_down(&mut self, pos: usize) { - let len = self.len(); - 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. - fn sift_down_to_bottom(&mut self, mut pos: usize) { - let end = self.len(); - let start = pos; - unsafe { - let mut hole = Hole::new(&mut self.data, pos); - let mut child = 2 * pos + 1; - while child < end { - let right = child + 1; - // compare with the greater of the two children - if right < end && hole.get(child) <= hole.get(right) { - child = right; - } - hole.move_to(child); - child = 2 * hole.pos() + 1; - } - pos = hole.pos; - } - self.sift_up(start, pos); - } - - fn rebuild(&mut self) { - let mut n = self.len() / 2; - while n > 0 { - n -= 1; - self.sift_down(n); - } - } - - /// Moves all the elements of `other` into `self`, leaving `other` empty. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// use std::collections::BinaryHeap; - /// - /// let v = vec![-10, 1, 2, 3, 3]; - /// let mut a = BinaryHeap::from(v); - /// - /// let v = vec![-20, 5, 43]; - /// let mut b = BinaryHeap::from(v); - /// - /// 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); - } - - if other.is_empty() { - return; - } - - #[inline(always)] - fn log2_fast(x: usize) -> usize { - 8 * size_of::<usize>() - (x.leading_zeros() as usize) - 1 - } - - // `rebuild` takes O(len1 + len2) operations - // and about 2 * (len1 + len2) comparisons in the worst case - // while `extend` takes O(len2 * log(len1)) operations - // and about 1 * len2 * log_2(len1) comparisons in the worst case, - // assuming len1 >= len2. - #[inline] - fn better_to_rebuild(len1: usize, len2: usize) -> bool { - 2 * (len1 + len2) < len2 * log2_fast(len1) - } - - if better_to_rebuild(self.len(), other.len()) { - self.data.append(&mut other.data); - self.rebuild(); - } else { - self.extend(other.drain()); - } - } - - /// Returns an iterator which retrieves elements in heap order. - /// The retrieved elements are removed from the original heap. - /// The remaining elements will be removed on drop in heap order. - /// - /// 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(vec![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` such that `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(vec![-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, f: F) - where - F: FnMut(&T) -> bool, - { - self.data.retain(f); - self.rebuild(); - } -} - -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(vec![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(vec![1, 2, 3, 4, 5]); - /// - /// assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), 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. - #[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); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn capacity(&self) -> usize { - self.data.capacity() - } - - /// Reserves the minimum capacity for exactly `additional` more elements to be inserted in the - /// given `BinaryHeap`. 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 [`reserve`] if future - /// insertions are expected. - /// - /// # 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`]: #method.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` more elements to be inserted in the - /// `BinaryHeap`. The collection may reserve more space to avoid frequent reallocations. - /// - /// # 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); - } - - /// 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. - /// - /// Panics if the current capacity is smaller than the supplied - /// minimum capacity. - /// - /// # Examples - /// - /// ``` - /// #![feature(shrink_to)] - /// 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] - #[unstable(feature = "shrink_to", reason = "new API", issue = "56431")] - pub fn shrink_to(&mut self, min_capacity: usize) { - self.data.shrink_to(min_capacity) - } - - /// Consumes the `BinaryHeap` and returns the underlying vector - /// in arbitrary order. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// use std::collections::BinaryHeap; - /// let heap = BinaryHeap::from(vec![1, 2, 3, 4, 5, 6, 7]); - /// let vec = heap.into_vec(); - /// - /// // Will print in some order - /// for x in vec { - /// println!("{}", x); - /// } - /// ``` - #[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(vec![1, 3]); - /// - /// assert_eq!(heap.len(), 2); - /// ``` - #[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()); - /// ``` - #[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. - /// - /// The elements are removed in arbitrary order. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// use std::collections::BinaryHeap; - /// let mut heap = BinaryHeap::from(vec![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(vec![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 index_ptr: *const _ = self.data.get_unchecked(index); - let hole_ptr = self.data.get_unchecked_mut(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 the [`iter`] method on [`BinaryHeap`]. See its -/// documentation for more. -/// -/// [`iter`]: struct.BinaryHeap.html#method.iter -/// [`BinaryHeap`]: struct.BinaryHeap.html -#[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 the [`into_iter`] method on [`BinaryHeap`] -/// (provided by the `IntoIterator` trait). See its documentation for more. -/// -/// [`into_iter`]: struct.BinaryHeap.html#method.into_iter -/// [`BinaryHeap`]: struct.BinaryHeap.html -#[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> {} - -#[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 the [`drain`] method on [`BinaryHeap`]. See its -/// documentation for more. -/// -/// [`drain`]: struct.BinaryHeap.html#method.drain -/// [`BinaryHeap`]: struct.BinaryHeap.html -#[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 the [`drain_sorted`] method on [`BinaryHeap`]. See its -/// documentation for more. -/// -/// [`drain_sorted`]: struct.BinaryHeap.html#method.drain_sorted -/// [`BinaryHeap`]: struct.BinaryHeap.html -#[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 = "binary_heap_extras_15", since = "1.5.0")] -impl<T> From<BinaryHeap<T>> for Vec<T> { - 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(vec![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<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); - } -} |