swift实现栈和队列

在swift中并没有内设的栈和队列，接下来我们通过数组来实现栈和队列

栈的实现代码如下：

protocol Stack {
    associatedtype Element
    //是否为空
    var isEmpty: Bool{ get }
    //栈的大小
    var Size: Int{ get }
    //栈顶元素
    var peek: Element? { get }
    //入栈
    mutating func push(_ newElement:Element)
    //出栈
    mutating func pop()->Element?
}

struct IntegerStack:Stack {
    typealias Element  = Int
    private var stack = [Element]()
    var isEmpty: Bool {return stack.isEmpty}
    var Size: Int {return stack.count}
    var peek: Int? {return stack.last}
    mutating func push(_ newElement: Int) {
        self.stack.append(newElement)
    }
    func pop() -> Int? {
        return stack.last
    }
}

队列的实现代码如下：

protocol Queue {
    associatedtype Element
    var isEmpty: Bool {get}
    var Size: Int {get}
    var Peek:Element? {get}
    mutating func enQueue(_ newElement:Element)
    mutating func deQueue()->Element?
}

struct IntergerQueue:Queue {
    typealias Element = Int
    private var left = [Element]()
    private var right = [Element]()
    var isEmpty: Bool {return left.isEmpty && right.isEmpty}
    var Size: Int {return left.count + right.count}
    var Peek: Element? {return left.isEmpty ? right.first : left.last}
    mutating func enQueue(_ newElement: Int) {
       right.append(newElement)
    }
    mutating func deQueue() -> Element? {
        if left.isEmpty {
            left = right.reversed()
            right.removeAll()
        }
        return left.popLast()
    }
}