# Struct binary_heap_plus::BinaryHeap

source · [−]`pub struct BinaryHeap<T, C = MaxComparator> { /* 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 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

The value for `push`

is an expected cost; the method documentation gives a
more detailed analysis.

## Implementations

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

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

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

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

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

#### 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`

.

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

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

source### impl<T: Ord> BinaryHeap<T>

### impl<T: Ord> BinaryHeap<T>

source#### pub fn new() -> Self

#### 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));
```

source#### pub fn with_capacity(capacity: usize) -> Self

#### 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));
```

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

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

source#### pub fn new_min() -> Self

#### 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));
```

source#### pub fn with_capacity_min(capacity: usize) -> Self

#### 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));
```

source### impl<T, F> BinaryHeap<T, FnComparator<F>>where

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

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

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

source#### pub fn new_by(f: F) -> Self

#### 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));
```

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

#### 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));
```

source### impl<T, F, K: Ord> BinaryHeap<T, KeyComparator<F>>where

F: Fn(&T) -> K,

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

F: Fn(&T) -> K,

source#### pub fn new_by_key(f: F) -> Self

#### 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));
```

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

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

`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));
```

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

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

source#### pub fn replace_cmp(&mut self, cmp: 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]);
```

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

#### 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.

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

#### 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).

source#### pub 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 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*)).

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

#### 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.

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

#### 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]);
```

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

#### 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());
```

source### impl<T, C> BinaryHeap<T, C>

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

source#### pub 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;`

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);
}
```

source#### pub fn into_iter_sorted(self) -> IntoIterSorted<T, C>ⓘNotable traits for IntoIterSorted<T, C>`impl<T, C: Compare<T>> Iterator for IntoIterSorted<T, C> type Item = T;`

#### pub fn into_iter_sorted(self) -> IntoIterSorted<T, C>ⓘNotable traits for IntoIterSorted<T, C>`impl<T, C: Compare<T>> Iterator for IntoIterSorted<T, C> type Item = T;`

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]);
```

source#### pub 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 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.

source#### pub fn capacity(&self) -> usize

#### 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);
```

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

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

source#### pub fn shrink_to_fit(&mut self)

#### 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);
```

source#### pub 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);
```

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

#### 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);
}
```

source#### pub fn len(&self) -> usize

#### 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);
```

source#### pub fn is_empty(&self) -> bool

#### 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());
```

source#### pub 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 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());
```

## Trait Implementations

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

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

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

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

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

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

source#### fn default() -> BinaryHeap<T>

#### fn default() -> BinaryHeap<T>

Creates an empty `BinaryHeap<T>`

.

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

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

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

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

source#### fn extend_one(&mut self, item: A)

#### fn extend_one(&mut self, item: A)

`extend_one`

)source#### fn extend_reserve(&mut self, additional: usize)

#### fn extend_reserve(&mut self, additional: usize)

`extend_one`

)source### impl<T, C: Compare<T>> Extend<T> for BinaryHeap<T, C>

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

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

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

source#### fn extend_one(&mut self, item: A)

#### fn extend_one(&mut self, item: A)

`extend_one`

)source#### fn extend_reserve(&mut self, additional: usize)

#### fn extend_reserve(&mut self, additional: usize)

`extend_one`

)source### impl<T, C> From<BinaryHeap<T, C>> for Vec<T>

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

source#### fn from(heap: BinaryHeap<T, C>) -> 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.

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

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

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

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

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

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

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

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

source#### fn 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 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);
}
```