pub struct BinaryHeap<T> { /* fields omitted */ }
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.
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())
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);
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.
impl<T> BinaryHeap<T> where
T: Ord,
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pub fn new() -> BinaryHeap<T>
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Creates an empty BinaryHeap
as a max-heap.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.push(4);
pub fn with_capacity(capacity: usize) -> BinaryHeap<T>
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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.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::with_capacity(10); heap.push(4);
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>>
[src]1.12.0
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.
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));
Cost is O(1) in the worst case.
pub fn pop(&mut self) -> Option<T>
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Removes the greatest item from the binary heap and returns it, or None
if it is empty.
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);
The worst case cost of pop
on a heap containing n elements is O(log(n)).
pub fn push(&mut self, item: T)
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Pushes an item onto the binary heap.
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));
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.
pub fn into_sorted_vec(self) -> Vec<T>ⓘNotable traits for Vec<u8>
impl Write for Vec<u8>
[src]1.5.0
Consumes the BinaryHeap
and returns a vector in sorted (ascending) order.
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]);
pub fn append(&mut self, other: &mut BinaryHeap<T>)
[src]1.11.0
Moves all the elements of other
into self
, leaving other
empty.
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());
pub fn drain_sorted(&mut self) -> DrainSorted<'_, T>ⓘNotable traits for DrainSorted<'_, T>
impl<'_, T> Iterator for DrainSorted<'_, T> where
T: Ord,
type Item = T;
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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.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);
pub fn retain<F>(&mut self, f: F) where
F: FnMut(&T) -> bool,
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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.
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])
impl<T> BinaryHeap<T>
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pub fn iter(&self) -> Iter<'_, T>ⓘNotable traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
type Item = &'a T;
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Returns an iterator visiting all values in the underlying vector, in arbitrary order.
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); }
pub fn into_iter_sorted(self) -> IntoIterSorted<T>ⓘNotable traits for IntoIterSorted<T>
impl<T> Iterator for IntoIterSorted<T> where
T: Ord,
type Item = T;
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Returns an iterator which retrieves elements in heap order. This method consumes the original heap.
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]);
pub fn peek(&self) -> Option<&T>
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Returns the greatest item in the binary heap, or None
if it is empty.
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));
Cost is O(1) in the worst case.
pub fn capacity(&self) -> usize
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Returns the number of elements the binary heap can hold without reallocating.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::with_capacity(100); assert!(heap.capacity() >= 100); heap.push(4);
pub fn reserve_exact(&mut self, additional: usize)
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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 if the new capacity overflows usize
.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.reserve_exact(100); assert!(heap.capacity() >= 100); heap.push(4);
pub fn reserve(&mut self, additional: usize)
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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 if the new capacity overflows usize
.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.reserve(100); assert!(heap.capacity() >= 100); heap.push(4);
pub fn shrink_to_fit(&mut self)
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Discards as much additional capacity as possible.
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);
pub fn shrink_to(&mut self, min_capacity: usize)
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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.
#![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);
pub fn into_vec(self) -> Vec<T>ⓘNotable traits for Vec<u8>
impl Write for Vec<u8>
[src]1.5.0
Consumes the BinaryHeap
and returns the underlying vector in arbitrary order.
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); }
pub fn len(&self) -> usize
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Returns the length of the binary heap.
Basic usage:
use std::collections::BinaryHeap; let heap = BinaryHeap::from(vec![1, 3]); assert_eq!(heap.len(), 2);
pub fn is_empty(&self) -> bool
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Checks if the binary heap is empty.
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());
pub fn drain(&mut self) -> Drain<'_, T>ⓘNotable traits for Drain<'_, T>
impl<'_, T> Iterator for Drain<'_, T>
type Item = T;
[src]1.6.0
Clears the binary heap, returning an iterator over the removed elements.
The elements are removed in arbitrary order.
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());
pub fn clear(&mut self)
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Drops all items from the binary heap.
Basic usage:
use std::collections::BinaryHeap; let mut heap = BinaryHeap::from(vec![1, 3]); assert!(!heap.is_empty()); heap.clear(); assert!(heap.is_empty());
impl<T> Clone for BinaryHeap<T> where
T: Clone,
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fn clone(&self) -> BinaryHeap<T>
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fn clone_from(&mut self, source: &BinaryHeap<T>)
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impl<T> Debug for BinaryHeap<T> where
T: Debug,
[src]1.4.0
impl<T> Default for BinaryHeap<T> where
T: Ord,
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fn default() -> BinaryHeap<T>
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Creates an empty BinaryHeap<T>
.
impl<'a, T> Extend<&'a T> for BinaryHeap<T> where
T: 'a + Ord + Copy,
[src]1.2.0
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
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fn extend_one(&mut self, &'a T)
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fn extend_reserve(&mut self, additional: usize)
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impl<T> Extend<T> for BinaryHeap<T> where
T: Ord,
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fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
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fn extend_one(&mut self, item: T)
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fn extend_reserve(&mut self, additional: usize)
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impl<T> From<BinaryHeap<T>> for Vec<T>
[src]1.5.0
fn from(heap: BinaryHeap<T>) -> Vec<T>ⓘNotable traits for Vec<u8>
impl Write for Vec<u8>
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impl<T> From<Vec<T>> for BinaryHeap<T> where
T: Ord,
[src]1.5.0
fn from(vec: Vec<T>) -> BinaryHeap<T>
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Converts a Vec<T>
into a BinaryHeap<T>
.
This conversion happens in-place, and has O(n) time complexity.
impl<T> FromIterator<T> for BinaryHeap<T> where
T: Ord,
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fn from_iter<I>(iter: I) -> BinaryHeap<T> where
I: IntoIterator<Item = T>,
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impl<'a, T> IntoIterator for &'a BinaryHeap<T>
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type Item = &'a T
The type of the elements being iterated over.
type IntoIter = Iter<'a, T>
Which kind of iterator are we turning this into?
fn into_iter(self) -> Iter<'a, T>ⓘNotable traits for Iter<'a, T>
impl<'a, T> Iterator for Iter<'a, T>
type Item = &'a T;
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impl<T> IntoIterator for BinaryHeap<T>
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type Item = T
The type of the elements being iterated over.
type IntoIter = IntoIter<T>
Which kind of iterator are we turning this into?
fn into_iter(self) -> IntoIter<T>ⓘNotable traits for IntoIter<T>
impl<T> Iterator for IntoIter<T>
type Item = T;
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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.
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); }
impl<T> RefUnwindSafe for BinaryHeap<T> where
T: RefUnwindSafe,
impl<T> Send for BinaryHeap<T> where
T: Send,
impl<T> Sync for BinaryHeap<T> where
T: Sync,
impl<T> Unpin for BinaryHeap<T> where
T: Unpin,
impl<T> UnwindSafe for BinaryHeap<T> where
T: UnwindSafe,
impl<T> Any for T where
T: 'static + ?Sized,
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impl<T> Borrow<T> for T where
T: ?Sized,
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fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
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impl<T> BorrowMut<T> for T where
T: ?Sized,
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fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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impl<I> IntoIterator for I where
I: Iterator,
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type Item = <I as Iterator>::Item
The type of the elements being iterated over.
type IntoIter = I
Which kind of iterator are we turning this into?
fn into_iter(self) -> I
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impl<T> ToOwned for T where
T: Clone,
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type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/collections/binary_heap/struct.BinaryHeap.html