Struct std::collections::BinaryHeap
1.0.0 · source · [−]pub struct BinaryHeap<T> { /* private fields */ }
Expand description
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 (it
could include panics, incorrect results, aborts, memory leaks, or
non-termination) but will not be undefined behavior.
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())
RunA BinaryHeap
with a known list of items can be initialized from an array:
use std::collections::BinaryHeap;
let heap = BinaryHeap::from([1, 5, 2]);
RunMin-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);
RunTime complexity
The value for push
is an expected cost; the method documentation gives a
more detailed analysis.
Implementations
sourceimpl<T> BinaryHeap<T> where
T: Ord,
impl<T> BinaryHeap<T> where
T: Ord,
sourcepub fn new() -> BinaryHeap<T>
pub fn new() -> BinaryHeap<T>
sourcepub fn with_capacity(capacity: usize) -> BinaryHeap<T>
pub fn with_capacity(capacity: usize) -> BinaryHeap<T>
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);
Run1.12.0 · sourcepub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>>
pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T>>
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));
RunTime complexity
If the item is modified then the worst case time complexity is O(log(n)), otherwise it’s O(1).
sourcepub fn pop(&mut self) -> Option<T>
pub fn pop(&mut self) -> Option<T>
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);
RunTime complexity
The worst case cost of pop
on a heap containing n elements is O(log(n)).
sourcepub fn push(&mut self, item: T)
pub fn push(&mut self, item: T)
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));
RunTime 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.
1.5.0 · sourcepub fn into_sorted_vec(self) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A: Allocator> Write for Vec<u8, A>
pub fn into_sorted_vec(self) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A: Allocator> Write for Vec<u8, A>
1.11.0 · sourcepub fn append(&mut self, other: &mut BinaryHeap<T>)
pub fn append(&mut self, other: &mut BinaryHeap<T>)
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());
Runsourcepub fn drain_sorted(&mut self) -> DrainSorted<'_, T>ⓘNotable traits for DrainSorted<'_, T>impl<'_, T> Iterator for DrainSorted<'_, T> where
T: Ord, type Item = T;
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;
T: Ord, type Item = T;
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);
Runsourcepub fn retain<F>(&mut self, f: F) where
F: FnMut(&T) -> bool,
pub fn retain<F>(&mut self, f: F) where
F: FnMut(&T) -> bool,
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])
Runsourceimpl<T> BinaryHeap<T>
impl<T> BinaryHeap<T>
sourcepub fn iter(&self) -> Iter<'_, T>ⓘNotable traits for Iter<'a, T>impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;
pub fn iter(&self) -> Iter<'_, T>ⓘNotable traits for Iter<'a, T>impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;
sourcepub fn into_iter_sorted(self) -> IntoIterSorted<T>ⓘNotable traits for IntoIterSorted<T>impl<T> Iterator for IntoIterSorted<T> where
T: Ord, type Item = T;
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;
T: Ord, type Item = T;
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]);
Runsourcepub fn peek(&self) -> Option<&T>
pub fn peek(&self) -> Option<&T>
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));
RunTime complexity
Cost is O(1) in the worst case.
sourcepub fn reserve_exact(&mut self, additional: usize)
pub fn reserve_exact(&mut self, additional: usize)
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);
Runsourcepub fn reserve(&mut self, additional: usize)
pub fn reserve(&mut self, additional: usize)
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);
Runsourcepub fn try_reserve_exact(
&mut self,
additional: usize
) -> Result<(), TryReserveError>
pub fn try_reserve_exact(
&mut self,
additional: usize
) -> Result<(), TryReserveError>
Tries to reserve the minimum capacity for exactly additional
elements to be inserted in the given BinaryHeap<T>
. 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.
Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
Examples
#![feature(try_reserve_2)]
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())
}
Runsourcepub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>
Tries to reserve capacity for at least additional
more elements to be inserted
in the given BinaryHeap<T>
. The collection may reserve more space to avoid
frequent reallocations. After calling try_reserve
, capacity will be
greater than or equal to self.len() + additional
. Does nothing if
capacity is already sufficient.
Errors
If the capacity overflows, or the allocator reports a failure, then an error is returned.
Examples
#![feature(try_reserve_2)]
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())
}
Runsourcepub fn shrink_to_fit(&mut self)
pub fn shrink_to_fit(&mut self)
1.56.0 · sourcepub fn shrink_to(&mut self, min_capacity: usize)
pub fn shrink_to(&mut self, min_capacity: usize)
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);
Runsourcepub fn as_slice(&self) -> &[T]ⓘNotable traits for &[u8]impl Read for &[u8]impl Write for &mut [u8]
pub fn as_slice(&self) -> &[T]ⓘNotable traits for &[u8]impl Read for &[u8]impl Write for &mut [u8]
1.5.0 · sourcepub fn into_vec(self) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A: Allocator> Write for Vec<u8, A>
pub fn into_vec(self) -> Vec<T, Global>ⓘNotable traits for Vec<u8, A>impl<A: Allocator> Write for Vec<u8, A>
1.6.0 · sourcepub fn drain(&mut self) -> Drain<'_, T>ⓘNotable traits for Drain<'_, T>impl<'_, T> Iterator for Drain<'_, T> type Item = T;
pub fn drain(&mut self) -> Drain<'_, T>ⓘNotable traits for Drain<'_, T>impl<'_, T> Iterator for Drain<'_, T> type Item = T;
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());
RunTrait Implementations
sourceimpl<T> Clone for BinaryHeap<T> where
T: Clone,
impl<T> Clone for BinaryHeap<T> where
T: Clone,
sourcefn clone(&self) -> BinaryHeap<T>
fn clone(&self) -> BinaryHeap<T>
Returns a copy of the value. Read more
sourcefn clone_from(&mut self, source: &BinaryHeap<T>)
fn clone_from(&mut self, source: &BinaryHeap<T>)
Performs copy-assignment from source
. Read more
1.4.0 · sourceimpl<T> Debug for BinaryHeap<T> where
T: Debug,
impl<T> Debug for BinaryHeap<T> where
T: Debug,
sourceimpl<T> Default for BinaryHeap<T> where
T: Ord,
impl<T> Default for BinaryHeap<T> where
T: Ord,
sourcefn default() -> BinaryHeap<T>
fn default() -> BinaryHeap<T>
Creates an empty BinaryHeap<T>
.
1.2.0 · sourceimpl<'a, T> Extend<&'a T> for BinaryHeap<T> where
T: 'a + Ord + Copy,
impl<'a, T> Extend<&'a T> for BinaryHeap<T> where
T: 'a + Ord + Copy,
sourcefn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = &'a T>,
Extends a collection with the contents of an iterator. Read more
sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
Reserves capacity in a collection for the given number of additional elements. Read more
sourceimpl<T> Extend<T> for BinaryHeap<T> where
T: Ord,
impl<T> Extend<T> for BinaryHeap<T> where
T: Ord,
sourcefn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
fn extend<I>(&mut self, iter: I) where
I: IntoIterator<Item = T>,
Extends a collection with the contents of an iterator. Read more
sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
Reserves capacity in a collection for the given number of additional elements. Read more
1.5.0 · sourceimpl<T> From<BinaryHeap<T>> for Vec<T, Global>
impl<T> From<BinaryHeap<T>> for Vec<T, Global>
1.5.0 · sourceimpl<T> From<Vec<T, Global>> for BinaryHeap<T> where
T: Ord,
impl<T> From<Vec<T, Global>> for BinaryHeap<T> where
T: Ord,
sourcefn from(vec: Vec<T, Global>) -> BinaryHeap<T>
fn from(vec: Vec<T, Global>) -> BinaryHeap<T>
Converts a Vec<T>
into a BinaryHeap<T>
.
This conversion happens in-place, and has O(n) time complexity.
sourceimpl<T> FromIterator<T> for BinaryHeap<T> where
T: Ord,
impl<T> FromIterator<T> for BinaryHeap<T> where
T: Ord,
sourcefn from_iter<I>(iter: I) -> BinaryHeap<T> where
I: IntoIterator<Item = T>,
fn from_iter<I>(iter: I) -> BinaryHeap<T> where
I: IntoIterator<Item = T>,
Creates a value from an iterator. Read more
sourceimpl<'a, T> IntoIterator for &'a BinaryHeap<T>
impl<'a, T> IntoIterator for &'a BinaryHeap<T>
sourceimpl<T> IntoIterator for BinaryHeap<T>
impl<T> IntoIterator for BinaryHeap<T>
sourcefn into_iter(self) -> IntoIter<T>ⓘNotable traits for IntoIter<T>impl<T> Iterator for IntoIter<T> type Item = T;
fn into_iter(self) -> IntoIter<T>ⓘNotable traits for IntoIter<T>impl<T> Iterator for IntoIter<T> type Item = 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}");
}
Runtype Item = T
type Item = T
The type of the elements being iterated over.
Auto Trait Implementations
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,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
Uses borrowed data to replace owned data, usually by cloning. Read more