Deque

public struct Deque<T>

A double-ended queue (deque) is a collection that generalizes a queue, for which elements can be added to or removed from either the front or back.

The enqueueFirst, enqueueLast, dequeueFirst and dequeueLast operations run in amortized constant time.

Conforms to Sequence, ExpressibleByArrayLiteral, CustomStringConvertible.

Creating a Deque

  • Constructs an empty deque.

    Declaration

    Swift

    public init()

  • Constructs a deque from a sequence, such as an array. The elements will be enqueued from first to last.

    Declaration

    Swift

    public init<S: Sequence>(_ elements: S) where S.Iterator.Element == T

Querying a Deque

  • Number of elements stored in the deque.

    Declaration

    Swift

    public var count : Int

  • Returns true if and only if count == 0.

    Declaration

    Swift

    public var isEmpty: Bool

  • The front element in the deque, or nil if the deque is empty.

    Declaration

    Swift

    public var first: T?

  • The back element in the deque, or nil if the deque is empty.

    Declaration

    Swift

    public var last: T?

Adding and Removing Elements

  • Inserts an element into the back of the deque.

    Declaration

    Swift

    public mutating func enqueueLast(_ element: T)

  • Inserts an element into the front of the deque.

    Declaration

    Swift

    public mutating func enqueueFirst(_ element: T)

  • Retrieves and removes the front element of the deque.

    Declaration

    Swift

    public mutating func dequeueFirst() -> T

    Return Value

    The front element, or nil if the deque is empty.

  • Retrieves and removes the back element of the deque.

    Declaration

    Swift

    public mutating func dequeueLast() -> T

    Return Value

    The back element, or nil if the deque is empty.

  • Removes all the elements from the deque, and by default clears the underlying storage buffer.

    Declaration

    Swift

    public mutating func removeAll(keepingCapacity keep: Bool = false)

Sequence Protocol Conformance

  • Provides for-in loop functionality. Generates elements in FIFO order.

    Declaration

    Swift

    public func makeIterator() -> AnyIterator<T>

    Return Value

    A generator over the elements.

ExpressibleByArrayLiteral Protocol Conformance

  • Constructs a deque using an array literal. The elements will be enqueued from first to last. let deque: Deque<Int> = [1,2,3]

    Declaration

    Swift

    public init(arrayLiteral elements: T...)

CustomStringConvertible Protocol Conformance

  • A string containing a suitable textual representation of the deque.

    Declaration

    Swift

    public var description: String