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

    pub struct BinaryHeap<T> {
        // some 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.

## Methods

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

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

Creates an empty `BinaryHeap` as a max-heap.

# Examples

fn main() { use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.push(4); }

    use std::collections::BinaryHeap;
    let mut heap = BinaryHeap::new();
    heap.push(4);

#### `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

fn main() { use std::collections::BinaryHeap; let mut heap = BinaryHeap::with_capacity(10); heap.push(4); }

    use std::collections::BinaryHeap;
    let mut heap = BinaryHeap::with_capacity(10);
    heap.push(4);

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

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

# Examples

fn main() { 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); } }

    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);
    }

#### `fn peek(&self) -> Option<&T>`

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

# Examples

fn main() { 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)); }

    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));

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

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

# Examples

fn main() { use std::collections::BinaryHeap; let mut heap = BinaryHeap::with_capacity(100); assert!(heap.capacity() >= 100); heap.push(4); }

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

#### `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

fn main() { use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.reserve_exact(100); assert!(heap.capacity() >= 100); heap.push(4); }

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

#### `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

fn main() { use std::collections::BinaryHeap; let mut heap = BinaryHeap::new(); heap.reserve(100); assert!(heap.capacity() >= 100); heap.push(4); }

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

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

Discards as much additional capacity as possible.

#### `fn pop(&mut self) -> Option<T>`

Removes the greatest item from the binary heap and returns it, or `None` if it is empty.

# Examples

fn main() { 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); }

    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);

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

Pushes an item onto the binary heap.

# Examples

fn main() { 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)); }

    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));

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

Unstable (`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

#![feature(binary_heap_extras)] fn main() { 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)); }

    #![feature(binary_heap_extras)]

    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));

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

Unstable (`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

#![feature(binary_heap_extras)] fn main() { 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)); }

    #![feature(binary_heap_extras)]

    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));

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

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

# Examples

fn main() { 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); } }

    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);
    }

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

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

# Examples

fn main() { 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]); }

    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]);

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

Returns the length of the binary heap.

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

Checks if the binary heap is empty.

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

Clears the binary heap, returning an iterator over the removed elements.

The elements are removed in arbitrary order.

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

Drops all items from the binary heap.

## Trait Implementations

### `impl<T> Clone for BinaryHeap<T> where T: Clone`

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

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

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

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

### `impl<T> Debug for BinaryHeap<T> where T: Ord + Debug`

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

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

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

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

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

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

#### `type Item = T`

#### `type IntoIter = IntoIter<T>`

#### `fn into_iter(self) -> IntoIter<T>`

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

#### `type Item = &'a T`

#### `type IntoIter = Iter<'a, T>`

#### `fn into_iter(self) -> Iter<'a, T>`

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

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

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

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

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize`)