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/Rust

Struct std::collections::VecDeque

pub struct VecDeque<T> { /* fields omitted */ }

A double-ended queue implemented with a growable ring buffer.

The "default" usage of this type as a queue is to use push_back to add to the queue, and pop_front to remove from the queue. extend and append push onto the back in this manner, and iterating over VecDeque goes front to back.

Methods

`impl<T> VecDeque<T>` [src]

`fn new() -> VecDeque<T>` [src]

Creates an empty VecDeque.

Examples

use std::collections::VecDeque;

let vector: VecDeque<u32> = VecDeque::new();

`fn with_capacity(n: usize) -> VecDeque<T>` [src]

Creates an empty VecDeque with space for at least n elements.

Examples

use std::collections::VecDeque;

let vector: VecDeque<u32> = VecDeque::with_capacity(10);

`fn get(&self, index: usize) -> Option<&T>` [src]

Retrieves an element in the VecDeque by index.

Element at index 0 is the front of the queue.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(3);
buf.push_back(4);
buf.push_back(5);
assert_eq!(buf.get(1), Some(&4));

`fn get_mut(&mut self, index: usize) -> Option<&mut T>` [src]

Retrieves an element in the VecDeque mutably by index.

Element at index 0 is the front of the queue.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(3);
buf.push_back(4);
buf.push_back(5);
if let Some(elem) = buf.get_mut(1) {
    *elem = 7;
}

assert_eq!(buf[1], 7);

`fn swap(&mut self, i: usize, j: usize)` [src]

Swaps elements at indices i and j.

i and j may be equal.

Element at index 0 is the front of the queue.

Panics

Panics if either index is out of bounds.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(3);
buf.push_back(4);
buf.push_back(5);
assert_eq!(buf, [3, 4, 5]);
buf.swap(0, 2);
assert_eq!(buf, [5, 4, 3]);

`fn capacity(&self) -> usize` [src]

Returns the number of elements the VecDeque can hold without reallocating.

Examples

use std::collections::VecDeque;

let buf: VecDeque<i32> = VecDeque::with_capacity(10);
assert!(buf.capacity() >= 10);

`fn reserve_exact(&mut self, additional: usize)` [src]

Reserves the minimum capacity for exactly additional more elements to be inserted in the given VecDeque. 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

use std::collections::VecDeque;

let mut buf: VecDeque<i32> = vec![1].into_iter().collect();
buf.reserve_exact(10);
assert!(buf.capacity() >= 11);

`fn reserve(&mut self, additional: usize)` [src]

Reserves capacity for at least additional more elements to be inserted in the given VecDeque. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new capacity overflows usize.

Examples

use std::collections::VecDeque;

let mut buf: VecDeque<i32> = vec![1].into_iter().collect();
buf.reserve(10);
assert!(buf.capacity() >= 11);

`fn shrink_to_fit(&mut self)`
1.5.0
[src]

Shrinks the capacity of the VecDeque as much as possible.

It will drop down as close as possible to the length but the allocator may still inform the VecDeque that there is space for a few more elements.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::with_capacity(15);
buf.extend(0..4);
assert_eq!(buf.capacity(), 15);
buf.shrink_to_fit();
assert!(buf.capacity() >= 4);

`fn truncate(&mut self, len: usize)`
1.16.0
[src]

Shortens the VecDeque, dropping excess elements from the back.

If len is greater than the VecDeque's current length, this has no effect.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(5);
buf.push_back(10);
buf.push_back(15);
assert_eq!(buf, [5, 10, 15]);
buf.truncate(1);
assert_eq!(buf, [5]);

`fn iter(&self) -> Iter<T>` [src]

Returns a front-to-back iterator.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(5);
buf.push_back(3);
buf.push_back(4);
let b: &[_] = &[&5, &3, &4];
let c: Vec<&i32> = buf.iter().collect();
assert_eq!(&c[..], b);

`fn iter_mut(&mut self) -> IterMut<T>` [src]

Returns a front-to-back iterator that returns mutable references.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(5);
buf.push_back(3);
buf.push_back(4);
for num in buf.iter_mut() {
    *num = *num - 2;
}
let b: &[_] = &[&mut 3, &mut 1, &mut 2];
assert_eq!(&buf.iter_mut().collect::<Vec<&mut i32>>()[..], b);

`fn as_slices(&self) -> (&[T], &[T])`
1.5.0
[src]

Returns a pair of slices which contain, in order, the contents of the VecDeque.

Examples

use std::collections::VecDeque;

let mut vector = VecDeque::new();

vector.push_back(0);
vector.push_back(1);
vector.push_back(2);

assert_eq!(vector.as_slices(), (&[0, 1, 2][..], &[][..]));

vector.push_front(10);
vector.push_front(9);

assert_eq!(vector.as_slices(), (&[9, 10][..], &[0, 1, 2][..]));

`fn as_mut_slices(&mut self) -> (&mut [T], &mut [T])`
1.5.0
[src]

Returns a pair of slices which contain, in order, the contents of the VecDeque.

Examples

use std::collections::VecDeque;

let mut vector = VecDeque::new();

vector.push_back(0);
vector.push_back(1);

vector.push_front(10);
vector.push_front(9);

vector.as_mut_slices().0[0] = 42;
vector.as_mut_slices().1[0] = 24;
assert_eq!(vector.as_slices(), (&[42, 10][..], &[24, 1][..]));

`fn len(&self) -> usize` [src]

Returns the number of elements in the VecDeque.

Examples

use std::collections::VecDeque;

let mut v = VecDeque::new();
assert_eq!(v.len(), 0);
v.push_back(1);
assert_eq!(v.len(), 1);

`fn is_empty(&self) -> bool` [src]

Returns true if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut v = VecDeque::new();
assert!(v.is_empty());
v.push_front(1);
assert!(!v.is_empty());

`fn drain<R>(&mut self, range: R) -> Drain<T> where R: RangeArgument<usize>,`
1.6.0
[src]

Create a draining iterator that removes the specified range in the VecDeque and yields the removed items.

Note 1: The element range is removed even if the iterator is not consumed until the end.

Note 2: It is unspecified how many elements are removed from the deque, if the Drain value is not dropped, but the borrow it holds expires (eg. due to mem::forget).

Panics

Panics if the starting point is greater than the end point or if the end point is greater than the length of the vector.

Examples

use std::collections::VecDeque;

let mut v: VecDeque<_> = vec![1, 2, 3].into_iter().collect();
let drained = v.drain(2..).collect::<VecDeque<_>>();
assert_eq!(drained, [3]);
assert_eq!(v, [1, 2]);

// A full range clears all contents
v.drain(..);
assert!(v.is_empty());

`fn clear(&mut self)` [src]

Clears the buffer, removing all values.

Examples

use std::collections::VecDeque;

let mut v = VecDeque::new();
v.push_back(1);
v.clear();
assert!(v.is_empty());

`fn contains(&self, x: &T) -> bool where T: PartialEq<T>,`
1.12.0
[src]

Returns true if the VecDeque contains an element equal to the given value.

Examples

use std::collections::VecDeque;

let mut vector: VecDeque<u32> = VecDeque::new();

vector.push_back(0);
vector.push_back(1);

assert_eq!(vector.contains(&1), true);
assert_eq!(vector.contains(&10), false);

`fn front(&self) -> Option<&T>` [src]

Provides a reference to the front element, or None if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
assert_eq!(d.front(), None);

d.push_back(1);
d.push_back(2);
assert_eq!(d.front(), Some(&1));

`fn front_mut(&mut self) -> Option<&mut T>` [src]

Provides a mutable reference to the front element, or None if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
assert_eq!(d.front_mut(), None);

d.push_back(1);
d.push_back(2);
match d.front_mut() {
    Some(x) => *x = 9,
    None => (),
}
assert_eq!(d.front(), Some(&9));

`fn back(&self) -> Option<&T>` [src]

Provides a reference to the back element, or None if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
assert_eq!(d.back(), None);

d.push_back(1);
d.push_back(2);
assert_eq!(d.back(), Some(&2));

`fn back_mut(&mut self) -> Option<&mut T>` [src]

Provides a mutable reference to the back element, or None if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
assert_eq!(d.back(), None);

d.push_back(1);
d.push_back(2);
match d.back_mut() {
    Some(x) => *x = 9,
    None => (),
}
assert_eq!(d.back(), Some(&9));

`fn pop_front(&mut self) -> Option<T>` [src]

Removes the first element and returns it, or None if the VecDeque is empty.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
d.push_back(1);
d.push_back(2);

assert_eq!(d.pop_front(), Some(1));
assert_eq!(d.pop_front(), Some(2));
assert_eq!(d.pop_front(), None);

`fn push_front(&mut self, value: T)` [src]

Prepends an element to the VecDeque.

Examples

use std::collections::VecDeque;

let mut d = VecDeque::new();
d.push_front(1);
d.push_front(2);
assert_eq!(d.front(), Some(&2));

`fn push_back(&mut self, value: T)` [src]

Appends an element to the back of the VecDeque.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(1);
buf.push_back(3);
assert_eq!(3, *buf.back().unwrap());

`fn pop_back(&mut self) -> Option<T>` [src]

Removes the last element from the VecDeque and returns it, or None if it is empty.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
assert_eq!(buf.pop_back(), None);
buf.push_back(1);
buf.push_back(3);
assert_eq!(buf.pop_back(), Some(3));

`fn swap_remove_back(&mut self, index: usize) -> Option<T>`
1.5.0
[src]

Removes an element from anywhere in the VecDeque and returns it, replacing it with the last element.

This does not preserve ordering, but is O(1).

Returns None if index is out of bounds.

Element at index 0 is the front of the queue.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
assert_eq!(buf.swap_remove_back(0), None);
buf.push_back(1);
buf.push_back(2);
buf.push_back(3);
assert_eq!(buf, [1, 2, 3]);

assert_eq!(buf.swap_remove_back(0), Some(1));
assert_eq!(buf, [3, 2]);

`fn swap_remove_front(&mut self, index: usize) -> Option<T>`
1.5.0
[src]

Removes an element from anywhere in the VecDeque and returns it, replacing it with the first element.

This does not preserve ordering, but is O(1).

Returns None if index is out of bounds.

Element at index 0 is the front of the queue.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
assert_eq!(buf.swap_remove_front(0), None);
buf.push_back(1);
buf.push_back(2);
buf.push_back(3);
assert_eq!(buf, [1, 2, 3]);

assert_eq!(buf.swap_remove_front(2), Some(3));
assert_eq!(buf, [2, 1]);

`fn insert(&mut self, index: usize, value: T)`
1.5.0
[src]

Inserts an element at index within the VecDeque, shifting all elements with indices greater than or equal to index towards the back.

Element at index 0 is the front of the queue.

Panics

Panics if index is greater than VecDeque's length

Examples

use std::collections::VecDeque;

let mut vec_deque = VecDeque::new();
vec_deque.push_back('a');
vec_deque.push_back('b');
vec_deque.push_back('c');
assert_eq!(vec_deque, &['a', 'b', 'c']);

vec_deque.insert(1, 'd');
assert_eq!(vec_deque, &['a', 'd', 'b', 'c']);

`fn remove(&mut self, index: usize) -> Option<T>` [src]

Removes and returns the element at index from the VecDeque. Whichever end is closer to the removal point will be moved to make room, and all the affected elements will be moved to new positions. Returns None if index is out of bounds.

Element at index 0 is the front of the queue.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(1);
buf.push_back(2);
buf.push_back(3);
assert_eq!(buf, [1, 2, 3]);

assert_eq!(buf.remove(1), Some(2));
assert_eq!(buf, [1, 3]);

`fn split_off(&mut self, at: usize) -> VecDeque<T>`
1.4.0
[src]

Splits the collection into two at the given index.

Returns a newly allocated Self. self contains elements [0, at), and the returned Self contains elements [at, len).

Note that the capacity of self does not change.

Element at index 0 is the front of the queue.

Panics

Panics if at > len

Examples

use std::collections::VecDeque;

let mut buf: VecDeque<_> = vec![1,2,3].into_iter().collect();
let buf2 = buf.split_off(1);
assert_eq!(buf, [1]);
assert_eq!(buf2, [2, 3]);

`fn append(&mut self, other: &mut VecDeque<T>)`
1.4.0
[src]

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

Panics

Panics if the new number of elements in self overflows a usize.

Examples

use std::collections::VecDeque;

let mut buf: VecDeque<_> = vec![1, 2].into_iter().collect();
let mut buf2: VecDeque<_> = vec![3, 4].into_iter().collect();
buf.append(&mut buf2);
assert_eq!(buf, [1, 2, 3, 4]);
assert_eq!(buf2, []);

`fn retain<F>(&mut self, f: F) where F: FnMut(&T) -> bool,`
1.4.0
[src]

Retains only the elements specified by the predicate.

In other words, remove all elements e such that f(&e) returns false. This method operates in place and preserves the order of the retained elements.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.extend(1..5);
buf.retain(|&x| x%2 == 0);
assert_eq!(buf, [2, 4]);

`fn place_back(&mut self) -> PlaceBack<T>` [src]

🔬 This is a nightly-only experimental API. (collection_placement #30172)placement protocol is subject to change

Returns a place for insertion at the back of the VecDeque.

Using this method with placement syntax is equivalent to push_back, but may be more efficient.

Examples

#![feature(collection_placement)]
#![feature(placement_in_syntax)]

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.place_back() <- 3;
buf.place_back() <- 4;
assert_eq!(&buf, &[3, 4]);

`fn place_front(&mut self) -> PlaceFront<T>` [src]

🔬 This is a nightly-only experimental API. (collection_placement #30172)placement protocol is subject to change

Returns a place for insertion at the front of the VecDeque.

Using this method with placement syntax is equivalent to push_front, but may be more efficient.

Examples

#![feature(collection_placement)]
#![feature(placement_in_syntax)]

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.place_front() <- 3;
buf.place_front() <- 4;
assert_eq!(&buf, &[4, 3]);

`impl<T> VecDeque<T> where T: Clone,` [src]

`fn resize(&mut self, new_len: usize, value: T)`
1.16.0
[src]

Modifies the VecDeque in-place so that len() is equal to new_len, either by removing excess elements or by appending clones of value to the back.

Examples

use std::collections::VecDeque;

let mut buf = VecDeque::new();
buf.push_back(5);
buf.push_back(10);
buf.push_back(15);
assert_eq!(buf, [5, 10, 15]);

buf.resize(2, 0);
assert_eq!(buf, [5, 10]);

buf.resize(5, 20);
assert_eq!(buf, [5, 10, 20, 20, 20]);

Trait Implementations

`impl<T> From<Vec<T>> for VecDeque<T>`
1.10.0
[src]

`fn from(other: Vec<T>) -> VecDeque<T>` [src]

Performs the conversion.

`impl<T> From<VecDeque<T>> for Vec<T>`
1.10.0
[src]

`fn from(other: VecDeque<T>) -> Vec<T>` [src]

Performs the conversion.

`impl<'a, T> IntoIterator for &'a VecDeque<T>` [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>` [src]

Creates an iterator from a value. Read more

`impl<T> IntoIterator for VecDeque<T>` [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>` [src]

Consumes the list into a front-to-back iterator yielding elements by value.

`impl<'a, T> IntoIterator for &'a mut VecDeque<T>` [src]

`type Item = &'a mut T`

The type of the elements being iterated over.

`type IntoIter = IterMut<'a, T>`

Which kind of iterator are we turning this into?

`fn into_iter(self) -> IterMut<'a, T>` [src]

Creates an iterator from a value. Read more

`impl<A> PartialOrd<VecDeque<A>> for VecDeque<A> where A: PartialOrd<A>,` [src]

`fn partial_cmp(&self, other: &VecDeque<A>) -> Option<Ordering>` [src]

This method returns an ordering between self and other values if one exists. Read more

`fn lt(&self, other: &Rhs) -> bool` [src]

This method tests less than (for self and other) and is used by the < operator. Read more

`fn le(&self, other: &Rhs) -> bool` [src]

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

`fn gt(&self, other: &Rhs) -> bool` [src]

This method tests greater than (for self and other) and is used by the > operator. Read more

`fn ge(&self, other: &Rhs) -> bool` [src]

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more