queue-playground.swift

import Foundation


public struct Queue<Element>
{
    private var storage: [Element]
    
    public init()
    {
        self.storage = [Element]()
    }
    
    public mutating func enqueue(_ element: Element) -> Void
    {
        self.storage.append(element)
    }
    
    public mutating func dequeue() -> Element?
    {
        return self.storage.removeFirst()
    }
    
    public func whosFirst() -> Element?
    {
        return self.storage.first
    }
}

//
// TEST
//

var queue = Queue<Int>()

queue.enqueue(1)
queue.enqueue(2)
queue.enqueue(3)
queue.enqueue(4)
queue.enqueue(5)

print(queue)

if let first = queue.whosFirst()
{
    print("First: \(first)")
}

print(queue)

if let sacar = queue.dequeue()
{
    print("Sacar: \(sacar)")
}

print(queue)

queue.enqueue(1)
print(queue)