How to make a number not repeat itself more than 2 times?

Question

everyone ! Lets say we have

let random = arc4random_uniform(6)

how do i make it not repeat the same number more then two times ? I tried doing it like this :

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))
}

But it didn't work. I am new to swift and i didn't find a topic about this on the new swift 3 code. Thank you !

Answer 1

First of all lets build a class to save the recent history of the selected values

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
    }

}

Next let build a Randomizer

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
    }
}

And finally let test it

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
}