ios - Generate a Swift array of nonrepeating random numbers

Question

I'd like to generate multiple different random numbers in Swift. Here is the procedure.

1. Set up an empty array
2. Generate a random number

3. Check if the array is empty
   a. If the array is empty, insert the random number
   b. If the array is not empty, compare the random number to the numbers in array
   i. If the numbers are the same, repeat 2
   ii. if the numbers are not the same, insert the random number and repeat 2

   import UIKit 
   
   //the random number generator
   func randomInt(min: Int, max:Int) -> Int {
       return min + Int(arc4random_uniform(UInt32(max - min + 1)))
   }
   
   var temp = [Int]()
   for var i = 0; i<4; i++ {
     var randomNumber = randomInt(1, 5)
     if temp.isEmpty{
       temp.append(randomNumber)
     } else {
     //I don't know how to continue...
    }
   }
   

Answer 1

If you use your method the problem is, that you will create a new random-number each time. So you possibly could have the same random-number 4 times and so your array will only have one element.

So, if you just want to have an array of numbers from within a specific range of numbers (for example 0-100), in a random order, you can first fill an array with numbers in 'normal' order. For example with for loop etc:

var min = 1
var max = 5
for var i = min; i<= max; i++ {
    temp.append(i)
}

After that, you can use a shuffle method to shuffle all elements of the array with the shuffle method from this answer:

func shuffle<C: MutableCollectionType where C.Index == Int>(var list: C) -> C {
    let count = countElements(list)
    for i in 0..<(count - 1) {
        let j = Int(arc4random_uniform(UInt32(count - i))) + i
        swap(&list[i], &list[j])
    }
    return list
}

Ater that you can do something like that:

shuffle(temp)        // e.g., [3, 1, 2, 4, 5]