如何使数字不超过2次

Question

大家！可以说我们有

let random = arc4random_uniform(6)

我如何使其不重复相同的数字，而不是两次？我尝试这样做：

let previousNumber = Int()
let lastNumber = Int ()
let random = Int(arc4random_uniform(6))
if random == previousNumber {
  lastNumber = previousNumber
} else {
previousNumber = random 
}
if random == lastNumber {
random = Int(arc4random_uniform(6))
}

，但它不起作用。我是Swift的新手，在新的Swift 3代码上没有找到有关此的主题。谢谢 ！

Answer 1

首先，让构建一个类以保存所选值的最新历史

class History {
    private let size: Int
    private var values = [Int]()
    init(size:Int) {
        self.size = size
    }
    func add(value: Int) {
        values.insert(value, at: 0)
        if values.count > size {
            values.removeLast()
        }
    }
    var repeatedValueOnFullHistory: Int? {
        guard Set(values).count <= 1 else { return nil }
        return values.first
    }
}

接下来让构建随机器

class Randomizer {
    private var allValues = [Int]()
    private var history: History
    init?(maxValue: Int) {
        guard maxValue > 0 else { return nil }
        self.allValues = Array(0...maxValue)
        self.history = History(size: maxValue + 1)
    }
    var next: Int {
        let excludedValue = history.repeatedValueOnFullHistory
        let allowedValues = allValues.filter { excludedValue != $0 }
        let randomIndex = Int(arc4random_uniform(UInt32(allowedValues.count)))
        let nextValue = allowedValues[randomIndex]
        history.add(value: nextValue)
        return nextValue
    }
}

最后让测试

if let r = Randomizer(maxValue: 6) {
    r.next // 6
    r.next // 2
    r.next // 1
    r.next // 4
    r.next // 6
    r.next // 4
    r.next // 1
}