Queue

Queue.swift

@@ -0,0 +1,41 @@
+import UIKit
+
+struct Queue<T> {
+
+    var array: [T] = []
+    init() {}
+
+    var isEmpty: Bool {
+        return array.isEmpty
+    }
+
+    var peek: T? {
+        return array.first
+    }
+
+    mutating func enqueue(_ element: T) -> Bool {
+        array.append(element)
+        return true
+    }
+
+    mutating func dequeue() -> T? {
+        return isEmpty ? nil : array.removeFirst()
+    }
+}
+
+extension Queue: CustomStringConvertible {
+    var description: String {
+        return String(describing: array)
+    }
+}
+
+var queue = Queue<Int>()
+
+queue.enqueue(10)
+queue.enqueue(20)
+queue.enqueue(30)
+queue.enqueue(40)
+print(queue)               //[10, 20, 30, 40]
+
+queue.dequeue()
+print(queue)               //[20, 30, 40]