Struct BinaryHeap

pub struct BinaryHeap<T, C = MaxComparator> { /* private fields */ }

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 binary_heap_plus::BinaryHeap;

// Type inference lets us omit an explicit type signature (which
// would be `BinaryHeap<i32, MaxComparator>` in this example).
let mut heap = BinaryHeap::new();

// We can use peek to look at the next item in the heap. In this case,
// there's no items in there yet so we get None.
assert_eq!(heap.peek(), None);

// Let's add some scores...
heap.push(1);
heap.push(5);
heap.push(2);

// Now peek shows the most important item in the heap.
assert_eq!(heap.peek(), Some(&5));

// We can check the length of a heap.
assert_eq!(heap.len(), 3);

// We can iterate over the items in the heap, although they are returned in
// a random order.
for x in &heap {
    println!("{}", x);
}

// If we instead pop these scores, they should come back in order.
assert_eq!(heap.pop(), Some(5));
assert_eq!(heap.pop(), Some(2));
assert_eq!(heap.pop(), Some(1));
assert_eq!(heap.pop(), None);

// We can clear the heap of any remaining items.
heap.clear();

// The heap should now be empty.
assert!(heap.is_empty())

A BinaryHeap with a known list of items can be initialized from an array:

use binary_heap_plus::BinaryHeap;

// This will create a max-heap.
let heap = BinaryHeap::from([1, 5, 2]);

Min-heap

BinaryHeap can also act as a min-heap without requiring Reverse or a custom Ord implementation.

use binary_heap_plus::BinaryHeap;

let mut heap = BinaryHeap::new_min();

// There is no need to wrap values in `Reverse`
heap.push(1);
heap.push(5);
heap.push(2);

// If we pop these scores now, they should come back in the reverse order.
assert_eq!(heap.pop(), Some(1));
assert_eq!(heap.pop(), Some(2));
assert_eq!(heap.pop(), Some(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.

Implementations

impl<T, C: Compare<T> + Default> BinaryHeap<T, C>

pub fn from_vec(vec: Vec<T>) -> Self

Generic constructor for BinaryHeap from Vec.

Because BinaryHeap stores the elements in its internal Vec, it’s natural to construct it from Vec.

impl<T, C: Compare<T>> BinaryHeap<T, C>

pub fn from_vec_cmp(vec: Vec<T>, cmp: C) -> Self

Generic constructor for BinaryHeap from Vec and comparator.

Because BinaryHeap stores the elements in its internal Vec, it’s natural to construct it from Vec.

pub unsafe fn from_vec_cmp_raw(vec: Vec<T>, cmp: C, rebuild: bool) -> Self

Generic constructor for BinaryHeap from Vec and comparator.

Because BinaryHeap stores the elements in its internal Vec, it’s natural to construct it from Vec.

Safety

User is responsible for providing valid rebuild value.

impl<T: Ord> BinaryHeap<T>

pub fn new() -> Self

Creates an empty BinaryHeap.

This default version will create a max-heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new();
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(5));

pub fn with_capacity(capacity: usize) -> Self

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.

This default version will create a max-heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::with_capacity(10);
assert_eq!(heap.capacity(), 10);
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(5));

impl<T: Ord> BinaryHeap<T, MinComparator>

pub fn new_min() -> Self

Creates an empty BinaryHeap.

The _min() version will create a min-heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new_min();
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(1));

pub fn with_capacity_min(capacity: usize) -> Self

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.

The _min() version will create a min-heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::with_capacity_min(10);
assert_eq!(heap.capacity(), 10);
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(1));

impl<T, F> BinaryHeap<T, FnComparator<F>>

where F: Fn(&T, &T) -> Ordering,

pub fn new_by(f: F) -> Self

Creates an empty BinaryHeap.

The _by() version will create a heap ordered by given closure.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new_by(|a: &i32, b: &i32| b.cmp(a));
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(1));

pub fn with_capacity_by(capacity: usize, f: F) -> Self

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.

The _by() version will create a heap ordered by given closure.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::with_capacity_by(10, |a: &i32, b: &i32| b.cmp(a));
assert_eq!(heap.capacity(), 10);
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(1));

impl<T, F, K: Ord> BinaryHeap<T, KeyComparator<F>>

where F: Fn(&T) -> K,

pub fn new_by_key(f: F) -> Self

Creates an empty BinaryHeap.

The _by_key() version will create a heap ordered by key converted by given closure.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new_by_key(|a: &i32| a % 4);
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(3));

pub fn with_capacity_by_key(capacity: usize, f: F) -> Self

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.

The _by_key() version will create a heap ordered by key coverted by given closure.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::with_capacity_by_key(10, |a: &i32| a % 4);
assert_eq!(heap.capacity(), 10);
heap.push(3);
heap.push(1);
heap.push(5);
assert_eq!(heap.pop(), Some(3));

impl<T, C: Compare<T>> BinaryHeap<T, C>

pub fn replace_cmp(&mut self, cmp: C)

Replaces the comparator of binary heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
use compare::Compare;
use std::cmp::Ordering;

struct Comparator {
    ascending: bool
}

impl Compare<i32> for Comparator {
    fn compare(&self,l: &i32,r: &i32) -> Ordering {
        if self.ascending {
            r.cmp(l)
        } else {
            l.cmp(r)
        }
    }
}

// construct a heap in ascending order.
let mut heap = BinaryHeap::from_vec_cmp(vec![3, 1, 5], Comparator { ascending: true });

// replace the comparor
heap.replace_cmp(Comparator { ascending: false });
assert_eq!(heap.into_iter_sorted().collect::<Vec<_>>(), [5, 3, 1]);

pub unsafe fn replace_cmp_raw(&mut self, cmp: C, rebuild: bool)

Replaces the comparator of binary heap.

Safety

User is responsible for providing valid rebuild value.

pub fn peek_mut(&mut self) -> Option<PeekMut<'_, T, C>>

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 binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new();
assert!(heap.peek_mut().is_none());

heap.push(1);
heap.push(5);
heap.push(2);
{
    let mut val = heap.peek_mut().unwrap();
    *val = 0;
}
assert_eq!(heap.peek(), Some(&2));

Time complexity

If the item is modified then the worst case time complexity is O(log(n)), otherwise it’s O(1).

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 binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::from([1, 3]);

assert_eq!(heap.pop(), Some(3));
assert_eq!(heap.pop(), Some(1));
assert_eq!(heap.pop(), None);

Time complexity

The worst case cost of pop on a heap containing n elements is O(log(n)).

pub fn push(&mut self, item: T)

Pushes an item onto the binary heap.

Examples

Basic usage:

use binary_heap_plus::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.

pub fn into_sorted_vec(self) -> Vec<T>

Consumes the BinaryHeap and returns a vector in sorted (ascending) order.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;

let mut heap = BinaryHeap::from([1, 2, 4, 5, 7]);
heap.push(6);
heap.push(3);

let vec = heap.into_sorted_vec();
assert_eq!(vec, [1, 2, 3, 4, 5, 6, 7]);

pub fn append(&mut self, other: &mut Self)

Moves all the elements of other into self, leaving other empty.

Examples

Basic usage:

use binary_heap_plus::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());

impl<T, C> BinaryHeap<T, C>

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator visiting all values in the underlying vector, in arbitrary order.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let heap = BinaryHeap::from([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, C>

Returns an iterator which retrieves elements in heap order. This method consumes the original heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let heap = BinaryHeap::from([1, 2, 3, 4, 5]);

assert_eq!(heap.into_iter_sorted().take(2).collect::<Vec<_>>(), [5, 4]);

pub fn peek(&self) -> Option<&T>

Returns the greatest item in the binary heap, or None if it is empty.

Examples

Basic usage:

use binary_heap_plus::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.

pub fn capacity(&self) -> usize

Returns the number of elements the binary heap can hold without reallocating.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::with_capacity(100);
assert!(heap.capacity() >= 100);
heap.push(4);

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 binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new();
heap.reserve_exact(100);
assert!(heap.capacity() >= 100);
heap.push(4);

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 binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::new();
heap.reserve(100);
assert!(heap.capacity() >= 100);
heap.push(4);

pub fn shrink_to_fit(&mut self)

Discards as much additional capacity as possible.

Examples

Basic usage:

use binary_heap_plus::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)

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);

pub fn into_vec(self) -> Vec<T>

Consumes the BinaryHeap and returns the underlying vector in arbitrary order.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let heap = BinaryHeap::from([1, 2, 3, 4, 5, 6, 7]);
let vec = heap.into_vec();

// Will print in some order
for x in vec {
    println!("{}", x);
}

pub fn len(&self) -> usize

Returns the length of the binary heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let heap = BinaryHeap::from([1, 3]);

assert_eq!(heap.len(), 2);

pub fn is_empty(&self) -> bool

Checks if the binary heap is empty.

Examples

Basic usage:

use binary_heap_plus::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>

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 binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::from([1, 3]);

assert!(!heap.is_empty());

for x in heap.drain() {
    println!("{}", x);
}

assert!(heap.is_empty());

pub fn clear(&mut self)

Drops all items from the binary heap.

Examples

Basic usage:

use binary_heap_plus::BinaryHeap;
let mut heap = BinaryHeap::from([1, 3]);

assert!(!heap.is_empty());

heap.clear();

assert!(heap.is_empty());

Trait Implementations

impl<T: Clone, C: Clone> Clone for BinaryHeap<T, C>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug, C> Debug for BinaryHeap<T, C>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Ord> Default for BinaryHeap<T>

fn default() -> BinaryHeap<T>

Creates an empty BinaryHeap<T>.

impl<'a, T: 'a + Copy, C: Compare<T>> Extend<&'a T> for BinaryHeap<T, C>

fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<T, C: Compare<T>> Extend<T> for BinaryHeap<T, C>

fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<T: Ord, const N: usize> From<[T; N]> for BinaryHeap<T>

fn from(arr: [T; N]) -> Self

use binary_heap_plus::BinaryHeap;

let mut h1 = BinaryHeap::from([1, 4, 2, 3]);
let mut h2: BinaryHeap<_> = [1, 4, 2, 3].into();
while let Some((a, b)) = h1.pop().zip(h2.pop()) {
    assert_eq!(a, b);
}

impl<T, C> From<BinaryHeap<T, C>> for Vec<T>

fn from(heap: BinaryHeap<T, C>) -> Vec<T>

Converts a BinaryHeap<T> into a Vec<T>.

This conversion requires no data movement or allocation, and has constant time complexity.

impl<T: Ord> From<Vec<T>> for BinaryHeap<T>

fn from(vec: Vec<T>) -> Self

Converts a Vec<T> into a BinaryHeap<T>.

This conversion happens in-place, and has O(n) time complexity.

impl<T: Ord> FromIterator<T> for BinaryHeap<T>

fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self

Creates a value from an iterator.

impl<'a, T, C> IntoIterator for &'a BinaryHeap<T, C>

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>

Creates an iterator from a value.

impl<T, C> IntoIterator for BinaryHeap<T, C>

fn into_iter(self) -> 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 binary_heap_plus::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);
}

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?