如何在Swift 4中防止函数生成相同的随机数集

Question

I developed some code to generate five arrays of six numbers between 1 and 49. I used arc4random_uniform(49) function to try to do just that. However, when appendArrays() is producing same set of number for all five loops.

 class six49: lottery {

    var price: Int
    var winner: [Int] = []

    override init(draws: Int, lines: Int){

        price = 3
        super.init(draws: draws, lines: lines)
        }

    func appendArrays(win: inout [Int], win2: inout [[Int]]) -> [[Int]] {

        while win2.count < lines {

            while win.count < 6 {

                let selection = arc4random_uniform(49)

                if win.contains(Int(selection)){
                    continue
                } else {
                    win.append(Int(selection))
                    win = win.sorted()

                }
            }

            win2.append(win)

        }

        return win2

    }

}


let result = six49(draws: 1, lines: 5)

var arr2: [[Int]] = []
var arr1: [Int] = []
var collection = result.appendArrays(win: &arr1,win2: &arr2)

print(collection)

Here is output:

[[11, 16, 27, 31, 37, 39], [11, 16, 27, 31, 37, 39], [11, 16, 27, 31, 37, 39], [11, 16, 27, 31, 37, 39], [11, 16, 27, 31, 37, 39]]

I have been looking everywhere to try to create different set of number every loop, but I can't seem to find any solution.

Answer 1

Your problem is that you never reinitialize the win array. Once it has 6 numbers, it never changes so you just keep appending the same win array to your win2 array of arrays.

Instead of passing win as an inout [Int] into your appendArrays method, create a new win array each time in your main loop.

func appendArrays(win2: inout [[Int]]) -> [[Int]] {

    while win2.count < lines {

        var win = [Int]()

        while win.count < 6 {

            let selection = arc4random_uniform(49)

            if win.contains(Int(selection)){
                continue
            } else {
                win.append(Int(selection))
                win = win.sorted()                    
            }
        }

        win2.append(win)            
    }

    return win2        
}

---

Also, it isn't clear why you're passing win2 in since appendArrays returns the final value anyway. You could just create win2 inside of the function.

Also, you can sort the array once before adding it to win2 .

If you want numbers in 1...49 then you need to add 1 to your arc4random_uniform(49) number.

func appendArrays() -> [[Int]] {
    var win2 = [[Int]]()

    while win2.count < lines {
        var win = [Int]()

        while win.count < 6 {
            let selection = Int(arc4random_uniform(49) + 1)

            if !win.contains(selection) {
                win.append(selection)
            }
        }

        win.sort()

        win2.append(win)
    }

    return win2
}