std::collections::BinaryHeap - Rust
Description: API documentation for the Rust `BinaryHeap` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, BinaryHeap

# Struct std::collections::BinaryHeap 1.0.0 [−] [src]

    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.

# 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())Run

## Methods

### `impl<T> BinaryHeap<T> where T: Ord`
[src]

#### `fn new() -> 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);Run

#### `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);Run

#### `fn iter(&self) -> Iter<T>`

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);
    }Run

#### `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));
    Run

#### `fn peek_mut(&mut self) -> Option<PeekMut<T>>`
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.

# 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));Run

#### `fn capacity(&self) -> usize`

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);Run

#### `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);Run

#### `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);Run

#### `fn shrink_to_fit(&mut self)`

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);Run

#### `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(vec![1, 3]);

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

#### `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));Run

#### `fn push_pop(&mut self, item: T) -> T`

Deprecated since 1.13.0

: use `peek_mut` instead

🔬 This is a nightly-only experimental API. (`binary_heap_extras` #28147)

needs to be audited

Pushes an item onto the binary heap, then pops the greatest item off the queue in an optimized fashion.

# Examples

Basic usage:

    #![feature(binary_heap_extras)]
    #![allow(deprecated)]

    use std::collections::BinaryHeap;
    let mut heap = BinaryHeap::new();
    heap.push(1);
    heap.push(5);

    assert_eq!(heap.push_pop(3), 5);
    assert_eq!(heap.push_pop(9), 9);
    assert_eq!(heap.len(), 2);
    assert_eq!(heap.peek(), Some(&3));Run

#### `fn replace(&mut self, item: T) -> Option<T>`

Deprecated since 1.13.0

: use `peek_mut` instead

🔬 This is a nightly-only experimental API. (`binary_heap_extras` #28147)

needs to be audited

Pops the greatest item off the binary heap, then pushes an item onto the queue in an optimized fashion. The push is done regardless of whether the binary heap was empty.

# Examples

Basic usage:

    #![feature(binary_heap_extras)]
    #![allow(deprecated)]

    use std::collections::BinaryHeap;
    let mut heap = BinaryHeap::new();

    assert_eq!(heap.replace(1), None);
    assert_eq!(heap.replace(3), Some(1));
    assert_eq!(heap.len(), 1);
    assert_eq!(heap.peek(), Some(&3));Run

#### `fn into_vec(self) -> Vec<T>`
1.5.0

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);
    }Run

#### `fn into_sorted_vec(self) -> Vec<T>`
1.5.0

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]);Run

#### `fn len(&self) -> usize`

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);Run

#### `fn is_empty(&self) -> bool`

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());Run

#### `fn drain(&mut self) -> Drain<T>`
1.6.0

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());Run

#### `fn clear(&mut self)`

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());Run

#### `fn append(&mut self, other: &mut BinaryHeap<T>)`
1.11.0

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());Run

## Trait Implementations

### `impl<T> Extend<T> for BinaryHeap<T> where T: Ord`
[src]

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

Extends a collection with the contents of an iterator. Read more

### `impl<'a, T> Extend<&'a T> for BinaryHeap<T> where T: 'a + Copy + Ord`
1.2.0
[src]

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

Extends a collection with the contents of an iterator. Read more

### `impl<T> From<Vec<T>> for BinaryHeap<T> where T: Ord`
[src]

#### `fn from(vec: Vec<T>) -> BinaryHeap<T>`

Performs the conversion.

### `impl<T> IntoIterator for BinaryHeap<T> where T: Ord`
[src]

#### `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>`

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);
    }Run

### `impl<'a, T> IntoIterator for &'a BinaryHeap<T> where T: Ord`
[src]

#### `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. Read more

### `impl<T> Clone for BinaryHeap<T> where T: Clone`
[src]

#### `fn clone(&self) -> BinaryHeap<T>`

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &BinaryHeap<T>)`

Performs copy-assignment from `source`. Read more

### `impl<'a, T> Placer<T> for &'a mut BinaryHeap<T> where T: 'a + Clone + Ord`
[src]

#### `type Place = BinaryHeapPlace<'a, T>`

🔬 This is a nightly-only experimental API. (`placement_new_protocol` #27779)

`Place` is the intermedate agent guarding the uninitialized state for `Data`. Read more

#### `fn make_place(self) -> &'a mut BinaryHeap<T>::Place`

🔬 This is a nightly-only experimental API. (`placement_new_protocol` #27779)

Creates a fresh place from `self`.

### `impl<T> Debug for BinaryHeap<T> where T: Ord + Debug`
1.4.0
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

### `impl<T> Default for BinaryHeap<T> where T: Ord`
[src]

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

Creates an empty `BinaryHeap<T>`.

### `impl<T> FromIterator<T> for BinaryHeap<T> where T: Ord`
[src]

#### `fn from_iter<I>(iter: I) -> BinaryHeap<T> where I: IntoIterator<Item=T>`

Creates a value from an iterator. Read more

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