/rust

Permalink
Find file Copy path
2a66355 Dec 26, 2018
3 contributors

Users who have contributed to this file
@Mark-Simulacrum @ordovicia @alexreg
Raw Blame History
1187 lines (1097 sloc) 33.7 KB
//! 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;
//! use std::usize;
//!
//! #[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::ops::{Deref, DerefMut};
use core::iter::{FromIterator, FusedIterator};
use core::mem::{swap, size_of, ManuallyDrop};
use core::ptr;
use core::fmt;
use slice;
use 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())
/// ```
#[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<'a, T: Ord + fmt::Debug> fmt::Debug for PeekMut<'a, 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<'a, T: Ord> Drop for PeekMut<'a, T> {
fn drop(&mut self) {
if self.sift {
self.heap.sift_down(0);
}
}
}
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
impl<'a, T: Ord> Deref for PeekMut<'a, T> {
type Target = T;
fn deref(&self) -> &T {
&self.heap.data[0]
}
}
#[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
impl<'a, T: Ord> DerefMut for PeekMut<'a, T> {
fn deref_mut(&mut self) -> &mut T {
&mut self.heap.data[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 + Ord> 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 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 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));
///
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn peek(&self) -> Option<&T> {
self.data.get(0)
}
/// 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));
/// ```
#[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,
})
}
}
/// 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)
}
/// 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);
/// ```
#[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));
/// ```
#[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 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()
}
/// 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);
}
/// 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();
}
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_2(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());
}
}
}
/// 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());
let elt = ptr::read(&data[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());
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());
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<'a, T> Drop for Hole<'a, 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<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, 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<'a, T> Clone for Iter<'a, T> {
fn clone(&self) -> Iter<'a, T> {
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()
}
}
#[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<'a, T> ExactSizeIterator for Iter<'a, T> {
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<'a, T> FusedIterator for Iter<'a, T> {}
/// An owning iterator over the elements of a `BinaryHeap`.
///
/// This `struct` is created by the [`into_iter`] method on [`BinaryHeap`][`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> {}
/// 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<'a, T: 'a> Iterator for Drain<'a, 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<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
#[inline]
fn next_back(&mut self) -> Option<T> {
self.iter.next_back()
}
}
#[stable(feature = "drain", since = "1.6.0")]
impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}
#[stable(feature = "binary_heap_extras_15", since = "1.5.0")]
impl<T: Ord> From<Vec<T>> for BinaryHeap<T> {
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: Ord> 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>
where T: Ord
{
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);
}
}
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);
for elem in iterator {
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());
}
}