ios - Swift 中的堆栈实现

Question

我是 Swift 和 iOS 编程的新手。

我正在尝试测试一个简单的算法并需要一个堆栈数组。不必花哨(Int 堆栈就可以)。

我从 The Swift Programming Language documentation 得到 Stack 实现:

struct IntStack {
    var items = [Int]()
    mutating func push(item: Int) {
        items.append(item)
    }
    mutating func pop() -> Int {
        return items.removeLast()
    }
    mutating func count() -> Int {
        return items.count
    }
    mutating func show() {
        println(items)
    }
}

计数和显示功能是我的贡献。但是当我尝试声明堆栈数组时出现错误...

var lines = IntStack()[5]

“IntStack”没有名为下标的成员

我猜它与 Optionals 有关，但可以弄清楚它是什么。

有什么帮助吗？

Answer 1

详情

• swift 5.1，Xcode 11.3.1

通用堆栈实现

Stackable protocol

protocol Stackable {
    associatedtype Element
    func peek() -> Element?
    mutating func push(_ element: Element)
    @discardableResult mutating func pop() -> Element?
}

extension Stackable {
    var isEmpty: Bool { peek() == nil }
}

Stack

struct Stack<Element>: Stackable where Element: Equatable {
    private var storage = [Element]()
    func peek() -> Element? { storage.last }
    mutating func push(_ element: Element) { storage.append(element)  }
    mutating func pop() -> Element? { storage.popLast() }
}

extension Stack: Equatable {
    static func == (lhs: Stack<Element>, rhs: Stack<Element>) -> Bool { lhs.storage == rhs.storage }
}

extension Stack: CustomStringConvertible {
    var description: String { "\(storage)" }
}
    
extension Stack: ExpressibleByArrayLiteral {
    init(arrayLiteral elements: Self.Element...) { storage = elements }
}

用法

var stack = Stack<Int>()
stack.push(1)
stack.push(2)
stack.push(3)
print(stack.peek())
print(stack.pop())
print(stack)
print(stack == Stack<Int>())
stack = [3,2,1]
print(stack)