Implemented Dequeue data structure

Author: eleev

Data Structures.playground/Pages/Dequeue.xcplaygroundpage/Contents.swift

@@ -0,0 +1,169 @@
+//: [Previous](@previous)
+
+import Foundation
+
+struct Dequeue<T> {
+    // MARK: - Private properties
+    
+    private var data: [T]
+    
+    // MARK: - Public properties
+    
+    public var count: Int {
+        return data.count
+    }
+    
+    public var capacity: Int {
+        get {
+            return data.capacity
+        }
+        set {
+            data.reserveCapacity(capacity)
+        }
+    }
+    
+    // MARK: - Initializers
+    
+    public init() {
+        data = []
+    }
+    
+    public init<S: Sequence>(_ elements: S) where S.Iterator.Element == T {
+        self.init()
+        data.append(contentsOf: elements)
+    }
+    
+    // MARK: - Methods
+    
+    public mutating func dequeueFront() -> T? {
+        return data.removeFirst()
+    }
+    
+    public mutating func dequeueBack() -> T? {
+        return data.removeLast()
+    }
+    
+    public mutating func enqueue(front element: T) {
+        data.insert(element, at: 0)
+    }
+    
+    public mutating func enqueue(back element: T) {
+        data.append(element)
+    }
+    
+    public mutating func clear() {
+        data.removeAll()
+    }
+    
+    public mutating func isFull() -> Bool {
+        return count == data.capacity
+    }
+    
+    public func isEmpty() -> Bool {
+        return data.isEmpty
+    }
+    
+    public func peekFirst() -> T? {
+        return data.first
+    }
+    
+    public func peekLast() -> T? {
+        return data.last
+    }
+    
+    // MARK: - Private methods
+    
+    private  func checkIndex(index: Int) throws {
+        if index < 0 || index > count {
+            throw DequeueError.indexOutOfRange
+        }
+    }
+}
+
+enum DequeueError: Error {
+    case indexOutOfRange
+}
+
+extension Dequeue: CustomStringConvertible, CustomDebugStringConvertible {
+    
+    public var description: String {
+        return data.description
+    }
+    
+    public var debugDescription: String {
+        return data.description
+    }
+}
+
+extension Dequeue: ExpressibleByArrayLiteral {
+    
+    public init(arrayLiteral elements: T...) {
+        self.init(elements)
+    }
+}
+
+extension Dequeue: Sequence {
+    
+    public func makeIterator() -> AnyIterator<T> {
+        let indexedIterator = IndexingIterator(_elements: data.lazy)
+        return AnyIterator(indexedIterator)
+    }
+    
+    public func generate() -> AnyIterator<T> {
+        let indexingIteratoer = IndexingIterator(_elements: data.lazy)
+        return AnyIterator(indexingIteratoer)
+        
+    }
+}
+
+
+extension Dequeue: MutableCollection {
+    
+    // MARK: - Core protocol conformance
+    
+    public var startIndex: Int {
+        return 0
+    }
+    
+    public var endIndex: Int {
+        return count - 1
+    }
+    
+    public func index(after i: Int) -> Int {
+        return data.index(after: i)
+    }
+    
+    // MARK: - Subscript implementation
+    
+    public subscript(index: Int) -> T {
+        get {
+            checkHandledIndex(index: index)
+            return data[index]
+        }
+        set {
+            checkHandledIndex(index: index)
+            data[index] = newValue
+        }
+    }
+    
+    // MARK: - Utility method
+    
+    private func checkHandledIndex(index: Int) {
+        do {
+            try checkIndex(index: index)
+        } catch {
+            fatalError(error.localizedDescription)
+        }
+    }
+}
+
+//: Usage:
+
+var dequeue = Dequeue([1,2,34,5,6,7])
+let back = dequeue.dequeueBack()
+let front = dequeue.dequeueFront()
+
+dequeue.enqueue(front: 99)
+dequeue.enqueue(back: 99)
+
+//: [Next](@next)

Data Structures.playground/contents.xcplayground

@@ -13,5 +13,6 @@
         <page name='BinaryTree'/>
         <page name='BinarySearchTree'/>
         <page name='Red-Black Tree'/>
+        <page name='Dequeue'/>
     </pages>
 </playground>