Struct std::collections::BinaryHeap

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())

Methods

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

pub 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);

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);

Important traits for Iter<'a, T>

impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;

pub 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);
}

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));

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));

pub 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);

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);

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);

pub 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);

pub fn shrink_to(&mut self, min_capacity: usize)

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

new API

Discards capacity with a lower bound.

The capacity will remain at least as large as both the length and the supplied value.

Panics if the current capacity is smaller than the supplied minimum capacity.

Examples

#![feature(shrink_to)]
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 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);

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));

Important traits for Vec<u8>

impl Write for Vec<u8>

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

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);
}

Important traits for Vec<u8>

impl Write for Vec<u8>

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

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]);

pub 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);

pub 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());

Important traits for Drain<'a, T>

impl<'a, T> Iterator for Drain<'a, T> where
    T: 'a,  type Item = T;

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

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());

pub 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());

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 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());

Trait Implementations

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

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

Creates a value from an iterator.

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

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T> Debug for BinaryHeap<T> where     T: Ord + Debug,

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

Formats the value using the given formatter.

impl<T> IntoIterator for BinaryHeap<T> where     T: Ord,

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

Important traits for IntoIter<T>

impl<T> Iterator for IntoIter<T> type Item = T;

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);
}

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

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?

Important traits for Iter<'a, T>

impl<'a, T> Iterator for Iter<'a, T> type Item = &'a T;

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

Creates an iterator from a value.

impl<T> Extend<T> for BinaryHeap<T> where     T: Ord,

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

Extends a collection with the contents of an iterator.

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

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

Extends a collection with the contents of an iterator.

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

fn default() -> BinaryHeap<T>

Creates an empty BinaryHeap<T>.

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

Important traits for Vec<u8>

impl Write for Vec<u8>

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

Performs the conversion.

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

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

Performs the conversion.